Those LCDs have a complex initialization routine and very easily fall into an invalid state where they will just ignore commands, It could be running when the powerbank is "off" and picking up stray noise as commands. Another possibility is a bad solder joint, faulty connections have caused me hours of trouble with those displays especially when running in parallel mode (16 data lines to mess up).
Very much enjoyed this post. Very honest and as always you go into some depth. Maybe we need a post on fault finding. Your methodology and train of thought would be a gift from heaven. Well done Julian
Dean Greenhough Thanks very much Dean. I do enjoy fault finding - in fact it was my job for 13 years. The problem with fault finding videos is that you need something with a fault that can be fixed. So much stuff these days just can't be fixed.
When you said you were going to look at this, I thought I would buy one to learn how to use one. Now, as I would have thought I did something wrong if I built one, I am having second thoughts. You can't learn on something that is broke and you don't know why. I want one to learn how to use it to trouble shoot with it, so this as you said is a fail. Thanks for the video and can't wait for an update.
Could it be triggering the brown out detection on the microcontroller if the supply is doing odd things like starting at 3.7v then going up to 9v. I take it you have tried having the power bank already on and then plugging it in or using another 9v supply, a pp3 would probably be a good test to rule out any power supply stability issues. Did look an interesting product before it went foggy, so I hope you get to complete the demo.
I had looked at that same kit. I was planning on getting one but was looking for some reviews. I hope you get the issue fixed and your scope kit working. Looking forward to seeing what the issue ends up being.
The LEDs on the display are directly driven from the supply (after the reverse polarity protection diode), which is why they always light up. For the rest of the circuit the supply has to go through voltage regulators which have considerable voltage drop (at least as soon as some current is flowing). Especially all the 3.3V part, which has a diode and two regulators in series (supply -> diode -> 5V -> 3.3V) won't get any voltage until you supply at least 6 or 7 volts. So the powerbank won't break anything. If it could it would be very, very bad design of the DSO. There's always the possibility that a power supply fails (or takes quite some time to ramp up). That might make the micro choke and a rest is needed, but it should never kill the hardware. Maybe the micro hangs at initializing the display and generating the pulses for the negative voltage comes after that. If you are unlucky and applied a negative voltage at the signal input while the opamp had no negative power, you might have fried the opamp though. Opamps really don't like to have voltages at their inputs which are outside the supply rails!
Julian Ilett I agree with what Billy Sugger has already suggested but also add that most circuits can tolerate "slow" power ups but "slow" is still sub 1 second. If a circuit is going to need to tolerate under voltages you have to design for that a bit and it looks like that "scope" wasn't designed to sit at a low voltage long before being damaged. When ever I build a circuit, especially one that took hours to assemble, I try to always use a half decent PS that I can rely on and that has some kind of current limiting or shut down protection. I'm sure that USB PS can supply many times (10+ x) more current than required for that scope so it isn't going to shutdown before the smoke escapes. Using a better PS for initial testing at least will eliminate any doubts and when you later try it with a different PS you already know that it did work before and can try again on the good PS. The first thing you normally check when first turning on a circuit is the PS outputs and if the controller is doing some kind of POST it very likely would be checking those and halting before doing anything with the display. Little surprised the LED doesn't blink different for different POST failures. I would desolder the L1 lead at V- and apply ~ -8 V to the input of the 7905 and check its output. It looks like the controller checks for about 2.3 V on V-MON (hard to see) and may adjust its output on VGEN as a result. See what happens with VGEN and the 7905 output when supplying your own -8 V negative supply. Good luck and keep us informed of your progress!
Had one of these recently, seems to work pretty well (considering the price paid!), wouldn't imagine it being used as a proper measuring tool though. Got a low-end Siglent scope shortly after, but keeping this one.
check that your 79L05 isnt a 78 because i had that they sent me 2x 78 not 1 of each! i got all my voltages except -5V and i had the 0.6v you are getting. however i had the problem with my display but i managed to get it working and i still had these issues but al lthe other voltages were ok apart from V1 V2 and the -5V not present
Some tips based on my experience on the Jyetech oscilloscope (model DSO 062, with a simple 128x64 LCD dot matrix display and ATMega 64): 1. Check for proper soldering on every joint you have made. Especially if you have a low powered iron. I prefer using a 40W iron rather than a 15W one some people use, because it heats up large pieces of metal very quickly and makes soldering on the ground plane very easy. However it is also easy to burn out stuff :). But I think than it is even easier to burn out stuff with a 15W iron because you need sometimes to keep it applied for more than the 5 seconds most packages are rated at. 2. More importantly, check if Vgen is present by probing the MCU pin directly. Try resoldering the MCU if it still does not work (there was a bad solder joint on the Atmega so the display would appear garbled) 3. Try attaching the USB to a PC (assuming it has USB connectivity) and see if it enumerates. If it does then probably the microcontroller is very fine :D 4. Try supplying -5.5V to the LM7905. Watch out for the dropout voltage of the regulator! 5. Try using a non-switching power supply, eg 7809 or battery. 6. Check all decoupling capacitors 7. Check out Jyetech's website - usually they've got troubleshooting guides with all teh voltage references you should check to see if it is working properly. www.jyetech.com/Products/LcdScope/e138.php It also says it's a 320x240 display. This is the full version of the manual, www.jyetech.com/Products/LcdScope/UserManual_138.pdf at page 2 there is a chart with all the voltages that are supposed to be present. Best luck :)
MrOpenGL Thanks for that - I'd done most of it :) Just tried connecting the USB - Windows sees it , but there's almost no intelligible data (VID is 0000, PID is 0002) and no driver can be found (predictably). I worked out that the display is 320x240 by counting ten pixels, then imagining it multiplied by 32 - looks about right!
Julian Ilett Manufacturer states: usb port has no functionality, present for future use. Read instructions and measure elements before soldering. Do not rush.
I had the exact same voltages and behaviour (that is before your screen went out) and I had misplaced the regulators, that is I put the 7905 where the 7805 was supposed to go and vice versa. One of them didn't survive the ordeal but after I corrected the placement and swapped the broken one I got proper voltages and the trace showed up. Just my 2 cents. Thanks and keep up the good work!
It works fine, just double check. tripple check.R11 150 ohm.R38 1.5K. double check soldering, It's very delicate. I made the mistake myself confusing the two REGULATORS 79L05 and 78L05. Then it worked fine.
I'm building one of these for a bit of fun as soon as it arrives, I'll video the process and hopefully I'll have a bit more luck. A temperature controlled iron is absolutely essential, especially for those points where you need to get extra heat, I also find it's a lot less prone to losing heat.
*Edit - Seems its a newer version they sent me - and I saw your newer videos - glad you got it working - noise isn't as bad on the version I have* Just made one last night - for the SMDs I used solder paste and a big old heat gun to melt it. Board was very toasty, but it made a neat job of it - chip survived and worked first time. Reading those resisters was though so I did what the instructions suggested and measured them all as the went in. I received More instructions than you did.... 3 Sheets - (1) An SMT Component installation Guide (2) The guide for soldering the larger stuff (3) A User Guide with the schematic you found printed on the back. The User guide has some hidden feature tips like - Factory Default (Hold + and - ) - which I had to use once when the 0V Line Alignment (Hold Sel for 2 secs when ms is selected) completely messed up. However my scope seems to add a little offset - a 0V reads as 0.6v - quite a lot of error of an offset.
That 9v power bank might have overshot the voltage when ramping 3.7v to 9v. There is prob not protection on the board to stop it. A short 15v overshoot will kill the microcontroller, or at least pieces of it.
Sorry forgot to mention. I found the switches were rather badly contaminated, (guessing oil). So it's just possible you have a bad solder joint. I'd definitely be checking your switches. Run over them again with your soldering iron and maybe check with some good magnification. After soldering in the first switch and finding it reluctant to take solder I went over the rest with a small strip of fine wet and dry and used some flux paste. A fiddly job but well worth the effort..
I finished mine this afternoon and it worked first up. A little bit of tweaking and it's working well. Not exactly the most complicated kit I've tackled, but I definitely needed a little magnification checking those tiny resistors. An excellent kit for $19.50 USD. I was impressed with the display, good resolution for the size. The inbuilt oscillator is a handy thing to have as well. I just wish someone had a suitable box to put it in, although it would mean remotely wiring all those buttons and switches. I was thinking of buying another kit specifically for for that purpose rather than trying to de-solder all those connections.
i recently bought one of the upgraded kits (13803k) and after building it it works perfectly, it has a little noise but within tolerance for a kit of such a price. i did all the soldering without using static protection (i did touch an earthed source before hand) and had no problems after. i think this is that 1 in 1000 chance to have a defective part that is with everything from tvs to mobile phones
I had a SMB version of this kit, and got it working fine. It is a great little project. I agree with some of the others here, 9V does not seem to cut it as a power supply, but 12V is solid.
I just got one of these pre-assembled for $15CAD. I'm pretty happy with it for the price. Wanna get an actual kit and build one once I get a better soldering iron.
I was thinking of getting one of these so I watched with interest when you reviewed it. Think I will now wait and see what transpires!! I have found in the past a number of kits from China just use very basic manufacturers data sheets and exclude the extras that make it a safe working product. I guess that's the difference between a cheap kit and a named manufactured product.
It looks like the kits that are being offered now on Amazon are limited to soldering the mechanical parts and all the surface mount components are already installed.
I had the same "mysterious" problem when I built mine. Several minor problems corrected (SMT resistors not completely soldered) but still nothing worked.. I decided to reflash the program and that fixed the problem. There are two versions of the program on the Banggood site. I am running the modified version that gives numeric details about the wave form... Very clever.
This oscilloscope was my third soldering project (after a little 16-LED blinking heart and a simple digital clock) and it instantly worked. Ok - I have to admit that it took me 6 hours, I followed the instructions and i measured all the parts before placing them. I start getting the suspicion that the instruction to measure the resistors is not just there for raising multimeter sales. ;D Bottom line: It's sad that this great kit may get a bad reputation because of someone who seems like a professional but is not able to follow a simple, linear manual.
I think it's highly unlikely that you killed the LCD, it looks to me like it is just not getting any display signals, and the missing -V supply probably has something to do with it, or is a symptom of whatever's causing the malfunction.
You could try replacing the LM7905 regulator and see if that gets the -V supply working again, and maybe the transistor that's part of the -V supply circuitry as well, hope that helps.
It's very likely that ESD damage due to static from that suspiciously inadequate looking anti-static packaging (and/or careless handling we cringed at in the first video?) was the likely cause of the LCD (or its tiny driver circuit) failure. While it is possible this can be proved though very expensive investigation (requires an electron microscope and opening up the IC in the lab), the MFR should just replace it at no cost. Sometime a static discharge will just cause a glitch that requires software re-boot, but it's still a very good idea to take care because ESD damage can take several months to cause a failure if a very tiny hole (that gets punched by a very tiny spark) allows oxygen to enter, contaminate and eventually destroy the semiconductor layer/junction. BTW, back in the early days of 4000a/ae series C-MOS before internal protection design improvements, that was called “making the chip pregnant”! Use a wrist strap or better yet IMO, be meticulous in discharge/handling procedures.
A. R. Jasso I've had this issue before, I never use the stock electrons. Poorly machined crap. I only import hand made finely ground electrons from Canuckistan.
Is it just me or at 8:28 what I presume to be the ribbon cable to the screen looks pulled away at the top? Before and after this, it seems to be flush to the screen.
How clean is the output of your powerbank? The reason I ask is that I have a few microcontroller boards that refuse to work with one of my banggood powerbanks despite its output voltage looking ok on a meter. When I checked the supply on the scope there was a ton of noise on there causing all sorts of hang-ups and weird behaviour (the board, not me). I would test this again with a known clean linear PSU when you replace the screen just in case.........
Julian Ilett yep have a lot of them :D Around 10-15 pieces and one of those was this one i needed with the oscilloscope! Maybe write an email to bangood and they send you a new display! :)
A years ago, i tried these kinds of TFT and parallel them with the same parallel bus, which turns out if the flux is too much between the data bus pin, it actually shorted out the signal with such high frequency clock and data. Try probe the pin with a multimeter and see whether they have any short may tell the internal TFT driver is damage or not.
Measure the resistances, capacitors and inductors twice before placing them, some of the resistors shipped were way off, some were off by a factor of 10 (so i'm guessing they misread the last band) so i had to use my own resistors. I imagine that had something to do with it.
Julian Ilett Hmm did you only check for the pulse-train on the -av point? It would seem to me that that is the regulated output of the 7905. Try and see if you can find the pulstrain on the first mentioned resistor, from the back side.
Just a guess: I had an issue with this kind of displays, with multiple ones, powering the backlight straight from 5V or 3.3V supply the display just turned white, and at first I thought I was getting faulty displays. The problem seemed to be with the backlight, because once I used a pwm output from the microcontroller and could regulate voltage supplied to the backlight (or used a voltage divider), at certain point the display would return to normal operation. I did not investigate the exact cause of this, but it seemed that once a high enough voltage was applied, the backlight interfered with the pixels on the display turning everything maximum white. It could also be the current issue, maybe someone can confirm this.
Have they help you solve the issue with the screen? When you start this series again, could I suggest a few things I would like to see to make it complete. You could ask them while you are trying to get it fixed if they could send you the update firmware. I have 45 and they are suppose to be up to 49(50 but they changed r11 resistor and firmware and will not give out firmware 50) but only 36 and 40 on the manufacturer site. You might want to show how to do the update, and tell us where we can get the later them 40 update. You might want to ask them about the new 138 with the 50 firmware that is suppose to have less noise and maybe they would want to send one to you to show the difference? Just some suggestions. Hope they get yours sorted out. Thanks again for the videos.
Hello Julian. I bought also that dso138 and an acrylic case. If the dso boots, all voltages are ok but the screen is white blank, then, i had the same problem, i look for the test modus and later for the lcd/tft display. The display reacts on the slightest touch and goes white blank. I disconnected the display from its back lime and lift it a bit, so mechanical tensions are smaller to the flat cable.. Now it runs ok. I will not send it back, because i believe, there may come the same sh... back. So not our foult.
Well I could not wait even though yours did not work. You must have done Banggood some good as I ordered mine and everything is coming except the scope kit! They must have sold out. I have it coming so that when you get yours working, I can follow along with whatever you do with it. Thanks again and I hope you get yours fixed soon!!!!!!
Hi Julian, could it be that the failure of the minus voltage has somehow disabled the output from the ARM uP? Looking forwards to the next video. Kind Regards Bob
I think the display is fine maybe a few ports from the microcontroller got damaged for some reason. Is a 320x240 display see my last videos where I use a quite similar one for my new Solar BMS project. Mine is just the SPI version not the parallel one so less pins. You can try to unglued the PCB from the motherboard and look at the flat flex soldering. With so many pins for parallel maybe one of them had a bad solder joint.
***** I just re-made all the solder joints between the flat flex and the red PCB (underneath the LCD panel), but it's no different. If the LCD problem is damaged ports on the MCU, that would mean the 2 faults are actually just 1 - damaged MCU ports - it makes sense. But is the MCU really so fragile?
Julian Ilett Maybe your Batterybank overshot the voltage while boosting. I didn't think my 5V Atmel 328P/PU was so fragile but apparently 5.9V Managed to kill it dead. I guess it's to be expected when they're so damn complex. Hope you get it fixed up soon!
Julian Ilett Is enough for just one pin not to be soldered correctly on the microcontroller to not initialize the 16bit parallel LCD. I'm getting it has something to do with their external circuit and those power supplies for it. Maybe one of few of the ports got over 3.3V and damaged the internal protection diode of the port. The ESD was sure not a problem. I never cared about that and never had a IC of any type die because of that. And you climate is much more humid so chances of ESD are even more reduced. Look with a magnifying glass at the microcontroller pins. Maybe they send another unit. The LCD's are nice maybe you get a few (I think about 6 or 7$ for the 2.2" SPI ones with PCB on eBay based on ILI9341 controller) hey are quite nice do to high resolution. The parallel one require to many pins for the microcontroller. There are larger displays 2.4" 2.8" and I think even 3.2" all based on the ILI9341 but also all have the same 320x240 resolution this are realy popular at the moment a sort of replacement for the Nokia 5110
Julian Ilett The MCU is a STM32F103C8, almost the same as on a Naze32 (STM32F103CB) flight controller for example. While I have heard of people frying their FC board, it seems rare. And since the board is not only used by "electronic guys", but most often by people who just barely manage to solder, you could even say the MCU is quite sturdy. It has pretty much the same preotection measures in place as an AVR on an Arduino has and they don't fry that often either. My guess is still that the MCU is failing on initialization of the display (which seems to come before the negative voltage clock is initialized).
Julian !! In this cell phone dominated world - Where did you get that great selectable multi-voltage power bank?? I have searched everywhere - and can only find 5V / 9V auto-select units for charging cell phones. And the 5 volt version I have automatically turns off on low current applications (thinking the "charging" is completed). I'd love a 9 volt portable - battery powered - rechargable power supply like that !! Thanks for all you do !!!
A couple of thoughts, perhaps you should consider taking some ESD precautions ( feet in a bucket of water type of thing) when assembling circuits. Living room carpets can be killers and those green cutting mats are no help. And yes a temperature controlled iron would help. It's not so much the temperature control but the higher power (eg. 50W) that makes them better. The temperature control just prevents the higher power from overheating the circuit.
number 33 This kit was a real pig to solder, I've never had this much trouble before. I think the spokes on the grounded pads are too thick and too short, but that may be just me making excuses. Looks like I've been beaten into temperature-controlled iron submission! My ESD precautions are instinctive - touch something grounded before handling parts. But I suppose I should be SEEN to be taking the proper precautions. Maybe it's time to retire the cutting mat and get an ESD mat.
Julian Ilett On the subject of ESD precautions, here's a brilliant product, an anti-static wrist strap that's not only digital but wireless too. tinyurl.com/neecsxj Yes, I was googling "Anti-static matting", and it's expensive stuff. Surely there must be something that's naturally slightly conductive that would be cheaper like for instance black craft paper or maybe black bin-bags. Trouble is it's so difficult to measure such low levels of conductivity.
number 33 No offence but you must be joking. A wireless ESD Band? The whole point is it has a 9M Ohm WIRE going to ground... I don't see how having something electronically floating in the breeze will help at all
I ordered the pre-build one with the SMD already soldered. Therefore only 500 other parts needs to be soldered.... Anyhow. Mine works fine and have a lot of fun.
Make sure youre using a center positive power source. mine did this until i changes from a center negative power source to a center positive. A 9volt battery would also work
Have you had any luck getting it running or in getting banggood to send another scope or screen? I was hoping you would show us things we could or can do with it in our hobby. Good luck.
amtpdb1 I've fixed the missing negative analogue voltage (AV-). That was due to resistors fitted in the wrong locations - 120 ohms in horrible 4-band colour code reads the exact reverse of 10k :( I've asked Banggood for a new LCD - waiting for a reply.
Julian Ilett Thanks for getting back so quickly. It's hard to beleave that they are taking so long to get this resolved considering that they sent it to you for a review! You would have thought they would have just sent you another kit just so you would say how efficient they were to resolve issues! Have a nice weekend. But I am still waiting for you to show me how to use it!!!!!! (:-}
+Julian Ilett i soooo would have bought and built one of these if it had have worked for you. i'm still keen to see one working. Maybe if they don't send you the replacement (or new display) you can do a hammer destruction video of it - you might make enough cash from views to buy a replacement.
+chillzwinter I built the first model they had and then purchased the second model that they came out with that has better noise elimination. The manufacturer finally gave out the better software, so I will change both to the new software. I had a couple of problems. I had to change out a voltage regulator as I was getting the wrong voltage, and remove one chip and re-soldered it Jye does get back to you on their forum to resolve issues. One thing is that you need to get a 9 volt power supply as if you use a battery as most start off with, when the voltage drops everything goes haywire. Good luck
I really enjoy your videos Julian, including this one, but I'm always surprised by your lack of a current limited bench power supply! It's too easy to make a mistake when "building up" any PCB. Watch this space. (Well, your space).
Hi. Have you sorted this out yet? I believe that the instructions were a little unclear on JP4 having to be shorted out or it causes the display to not work properly.
So I tried a third one after a few minutes of use the screen just goes white. The 2nd one came back to life once but then turned white a few minutes after I used it. Not worth anything.
I had a similar problem with my LCD except mine never showed an image only displad white screen. The instruction stated that R36 should be checked. I checked it and it read 180 ohms replaced it and still wouldn't work. I decided to replace the resistor but only had a 220 ohm. I solder it in anyway and the display started working. Haven't had any problems after a couple of hours of use.
Just built mines today, I also have 0.687 V on the AV- However I have a working display and a trace. But the trace is either on the bottom of the screen or the top of the screen. Frustrating indeed. You can try to reflash the chip, it might just be a bug. One of the 16v 100uF capacitors actually went short circuit, I pull it out and replaced it with a 25v 100uF. Oh and I found out that this scope is very picky about input voltages and current. It wasn't happen when I fed it 9.00V at 500ma. It was screaming and making music. I changed the voltage to 9.39v and 1.00 A. No more noise and it worked just "fine". I used a KORAD Linear PS that I bought for $40.
Walter Boxhead JP3 JP4 are both shorted. JP3 connects the two ground together, and JP4 supplies power to the MCU. I thought it was the transistor, so i took it off the board and the transistor is fine. I'm getting 1.2v out of VGEN. I dont have another scope to help out.
You might want to test all the GND points on both the LCD and discrete components , like mentioned you did say you were having problems soldering them. For those sort of kits a good temperature controlled solder station is a mist, maybe look at getting one of the many Haiko clones on aliexpress?
Could you add in the video the schematic. I have it but parts of the schematic end with digital grounds. You could tell us what the difference is between the different grounds and anything else you might see to help the beginners. Thanks again.
Good evening Julian. I'd like you to ask Banggood about the display. Does he sell it separately I wonder? What is the resolution? Looks like a parallel (high speed?) interface.
Note , they have changed a resistor value which is not mentioned in the main assembly instructions, just on an extra bit of paper shoved in! Get it wrong and the sensitivity is very poor!Mine worked first time, luckily!
Is it worth trying to flash the later firmware to see if that is accepted? That'll show the microcontroller is working. It's a bit like it's failing to fully boot and initialise the screen.
Steve Cooper That would be worth a try - there's a link to a reflashing procedure document on jyetech's website. MrOpenGL supplied the address: www.jyetech.com/Products/LcdScope/e138.php
Check all your solder joints, had the same problem. Turned out to be a dry join on the lcd connector pins. Also there are two points that need shorting with solder, jp3 and jp4. Good luck and clean your iron 😜
My first one went up in a puff of smoke. I had to replace all three power regulators to get it running. Not sure if my board is the older type or not, and I'm also not sure if it need to be modified by linking the capacitors together or not? How can I tell?
[IF YOU DON'T WANT TO READ, THE SOLUTION IS THE SECOND LAST SENTENCE]I don't know if it really matters anymore, but I found the solution. I've had the same problem with my unit(led flashing correctly, screen not working), and after 1 year of sitting on the shelf, i found it while organizing, and decided to give troubleshooting a shot. I went about troubleshooting it as shown in the manual, and it turned on! For at least a little time. I found that if you fiddle around with the screen, bending it back and forth, it sometimes worked, and sometimes didn't. So I pulled the LCD with its metal casing and it was sitting directly on the top of the solder joints of the ribbon cable -.- . So I just stuck a bit of kapton tape on the solder joints, put the display back on with a bit of glue(as I had destroyed the double sided sticky tape by removing it), gave it power, and that solved the problem for real this time. Hope it helps somebody that is struggling with this issue.
just out of despair, because I had the same problem, I took off the metal plate, I removed the flexive tape from connections, and voila, it worked, thanks ...
If your having problems with the TFT display check & resolder the TFT header on the TFT and the main PCB. I let my mate solder it as he was eager to do it but found the display wasn't working & after checking with ohm meter found dry joints.
the DSO112A made by the same company is fucking excellent. it has very high build quality & is rather surprisingly sharp. comes with a built in lithium ion battery. i designed a 3D printable chassis for it that holds two 18650 batteries in parallel so it lasts forever. jyetech.com/dso-coral-112a-oscilloscope/ www.thingiverse.com/thing:4047330
Similar problem to me, and voltage verification doesn't work in the same Pins you revissed. Furthermore ...I did see some board in youtube and publicity with pre-soldering Micro resistenses and Chips... Unfortunately, my recived kit wasn't soldered this part
My kit arrived but I have not built it yet... every now and then I look at it with all those little SMD parts... and decide to do something else instead :) Hopefully I'll have better luck when I eventually get around to it. btw do you know what the UART connection lets you do?
***** Yes, I'd be interested to hear whether you have any trouble with yours. It seems you use the UART connection to upgrade the firmware - details here: www.jyetech.com/Products/LcdScope/DSO138_oscilloscope_upgrade.pdf
Julian Ilett Blank white screen. All symptoms same as yours except I never saw the proper screen ever, and no amount of fiddling with the switches will make the LED blink again after booting. Interestingly, I do get the correct AV- voltage of -5V when the screen is attached though (and 0.6V when screen not attached). I always did have a feeling I would be flushing 3 hours down the toilet, but for $20 it was worth a try.
***** I'm surprised - I thought it was just bad luck that my scope didn't work. I'm also hugely disappointed - the scope looks really useful... if the display worked! I've contacted Banggood - they said they'd pass the info onto their tech people. It'll be interesting to hear the response.
***** Hmm, that's interesting - I don't think mine does that, but I'll have another look. I really can't decide if it's the MCU or the LCD that's failed. The additional problem of no -ve voltage pulses makes me suspect the MCU more than the LCD, but I have no idea why it worked for 2 minutes then turned its toes up. Your video looks like some control signals are getting into the LCD though. A replacement kit would help me resolve this, but Banggood have so far only suggested using a different power source (which I'll try of course). I'm sure if I nag them, they'll send another kit!
Ive resolved any issues ive had with the parts and the construction of my kit is complete and is running without issues , Calibrating it is a bit fun tho
Likely that you over volted the screen, sometimes in cheap devices the power for the screen is taken from the input before the voltage control for the MCU. I'm guessing the justification for that would be bc its draws more powe prhaps? The MCU isnt getting feedback from the screen so its not going to initalise the clocks needed for measurement. The test signal is likly to be using a hardware timer and interupt so the MCU wouldnt need to be fully booted up for it to give the signal. I would try plugging that screen into an arduino and running some example programs or piggyback a known good screen onto the board. That way you will know if you over volted the screen or the MCU.
Hi I have exactly the same fault, I think they use a replacement lcd with a different initialisation routine. I hope you find the problem or Bangood opens the firmware so I can debug it.
What you want to do is buy yourself a good strong magnifying loupe and use it to give each solder-joint a good close eyeball and check that they are all good, and there are no unintentional short-circuits, or solder-bridges, or dry solder-joints, I've got to the point where I always use a good temperature controlled soldering station whenever I do any soldering now, I'm looking at buying one of these Digital Scope kits from Banggood soon, it will be going in a big analog Modular Synthesizer which I'm in the process of building.
Just built one of these from Ebay and, much to my surprise, it worked at first power-up, the only snag is that the probe compensation capacitor on the 1 volt range doesn't seem to do anything. Any idea as to the use of the USB connector?
Those LCDs have a complex initialization routine and very easily fall into an invalid state where they will just ignore commands, It could be running when the powerbank is "off" and picking up stray noise as commands. Another possibility is a bad solder joint, faulty connections have caused me hours of trouble with those displays especially when running in parallel mode (16 data lines to mess up).
Very much enjoyed this post. Very honest and as always you go into some depth. Maybe we need a post on fault finding. Your methodology and train of thought would be a gift from heaven. Well done Julian
Dean Greenhough Thanks very much Dean. I do enjoy fault finding - in fact it was my job for 13 years. The problem with fault finding videos is that you need something with a fault that can be fixed. So much stuff these days just can't be fixed.
When you said you were going to look at this, I thought I would buy one to learn how to use one. Now, as I would have thought I did something wrong if I built one, I am having second thoughts. You can't learn on something that is broke and you don't know why. I want one to learn how to use it to trouble shoot with it, so this as you said is a fail.
Thanks for the video and can't wait for an update.
Could it be triggering the brown out detection on the microcontroller if the supply is doing odd things like starting at 3.7v then going up to 9v. I take it you have tried having the power bank already on and then plugging it in or using another 9v supply, a pp3 would probably be a good test to rule out any power supply stability issues. Did look an interesting product before it went foggy, so I hope you get to complete the demo.
I had looked at that same kit. I was planning on getting one but was looking for some reviews. I hope you get the issue fixed and your scope kit working. Looking forward to seeing what the issue ends up being.
Would love if you will bring it to life once again and show all details how you would do it. Best regards,
The LEDs on the display are directly driven from the supply (after the reverse polarity protection diode), which is why they always light up. For the rest of the circuit the supply has to go through voltage regulators which have considerable voltage drop (at least as soon as some current is flowing). Especially all the 3.3V part, which has a diode and two regulators in series (supply -> diode -> 5V -> 3.3V) won't get any voltage until you supply at least 6 or 7 volts. So the powerbank won't break anything. If it could it would be very, very bad design of the DSO. There's always the possibility that a power supply fails (or takes quite some time to ramp up). That might make the micro choke and a rest is needed, but it should never kill the hardware.
Maybe the micro hangs at initializing the display and generating the pulses for the negative voltage comes after that. If you are unlucky and applied a negative voltage at the signal input while the opamp had no negative power, you might have fried the opamp though. Opamps really don't like to have voltages at their inputs which are outside the supply rails!
Amazing ! Can't wait for the next episode, what a suspense !
Julian Ilett I agree with what Billy Sugger has already suggested but also add that most circuits can tolerate "slow" power ups but "slow" is still sub 1 second. If a circuit is going to need to tolerate under voltages you have to design for that a bit and it looks like that "scope" wasn't designed to sit at a low voltage long before being damaged.
When ever I build a circuit, especially one that took hours to assemble, I try to always use a half decent PS that I can rely on and that has some kind of current limiting or shut down protection. I'm sure that USB PS can supply many times (10+ x) more current than required for that scope so it isn't going to shutdown before the smoke escapes. Using a better PS for initial testing at least will eliminate any doubts and when you later try it with a different PS you already know that it did work before and can try again on the good PS.
The first thing you normally check when first turning on a circuit is the PS outputs and if the controller is doing some kind of POST it very likely would be checking those and halting before doing anything with the display. Little surprised the LED doesn't blink different for different POST failures.
I would desolder the L1 lead at V- and apply ~ -8 V to the input of the 7905 and check its output. It looks like the controller checks for about 2.3 V on V-MON (hard to see) and may adjust its output on VGEN as a result. See what happens with VGEN and the 7905 output when supplying your own -8 V negative supply.
Good luck and keep us informed of your progress!
Had one of these recently, seems to work pretty well (considering the price paid!), wouldn't imagine it being used as a proper measuring tool though. Got a low-end Siglent scope shortly after, but keeping this one.
check that your 79L05 isnt a 78 because i had that they sent me 2x 78 not 1 of each! i got all my voltages except -5V and i had the 0.6v you are getting. however i had the problem with my display but i managed to get it working and i still had these issues but al lthe other voltages were ok apart from V1 V2 and the -5V not present
Some tips based on my experience on the Jyetech oscilloscope (model DSO 062, with a simple 128x64 LCD dot matrix display and ATMega 64):
1. Check for proper soldering on every joint you have made. Especially if you have a low powered iron. I prefer using a 40W iron rather than a 15W one some people use, because it heats up large pieces of metal very quickly and makes soldering on the ground plane very easy. However it is also easy to burn out stuff :). But I think than it is even easier to burn out stuff with a 15W iron because you need sometimes to keep it applied for more than the 5 seconds most packages are rated at.
2. More importantly, check if Vgen is present by probing the MCU pin directly. Try resoldering the MCU if it still does not work (there was a bad solder joint on the Atmega so the display would appear garbled)
3. Try attaching the USB to a PC (assuming it has USB connectivity) and see if it enumerates. If it does then probably the microcontroller is very fine :D
4. Try supplying -5.5V to the LM7905. Watch out for the dropout voltage of the regulator!
5. Try using a non-switching power supply, eg 7809 or battery.
6. Check all decoupling capacitors
7. Check out Jyetech's website - usually they've got troubleshooting guides with all teh voltage references you should check to see if it is working properly. www.jyetech.com/Products/LcdScope/e138.php
It also says it's a 320x240 display.
This is the full version of the manual, www.jyetech.com/Products/LcdScope/UserManual_138.pdf at page 2 there is a chart with all the voltages that are supposed to be present.
Best luck :)
MrOpenGL Thanks for that - I'd done most of it :)
Just tried connecting the USB - Windows sees it , but there's almost no intelligible data (VID is 0000, PID is 0002) and no driver can be found (predictably).
I worked out that the display is 320x240 by counting ten pixels, then imagining it multiplied by 32 - looks about right!
Julian Ilett
Manufacturer states: usb port has no functionality, present for future use. Read instructions and measure elements before soldering. Do not rush.
I had the exact same voltages and behaviour (that is before your screen went out) and I had misplaced the regulators, that is I put the 7905 where the 7805 was supposed to go and vice versa. One of them didn't survive the ordeal but after I corrected the placement and swapped the broken one I got proper voltages and the trace showed up. Just my 2 cents.
Thanks and keep up the good work!
It works fine, just double check. tripple check.R11 150 ohm.R38 1.5K. double check soldering, It's very delicate. I made the mistake myself confusing the two REGULATORS 79L05 and 78L05. Then it worked fine.
Robert Moller hi friend my dso138 have white screen problem. and its 78l05 regulator is overheat i do not touch it. is it normal ?
and led blink when i connect it power supply a few seconds later it does not blink please help me friend
I'm building one of these for a bit of fun as soon as it arrives, I'll video the process and hopefully I'll have a bit more luck. A temperature controlled iron is absolutely essential, especially for those points where you need to get extra heat, I also find it's a lot less prone to losing heat.
*Edit - Seems its a newer version they sent me - and I saw your newer videos - glad you got it working - noise isn't as bad on the version I have*
Just made one last night - for the SMDs I used solder paste and a big old heat gun to melt it. Board was very toasty, but it made a neat job of it - chip survived and worked first time.
Reading those resisters was though so I did what the instructions suggested and measured them all as the went in.
I received More instructions than you did.... 3 Sheets - (1) An SMT Component installation Guide (2) The guide for soldering the larger stuff (3) A User Guide with the schematic you found printed on the back.
The User guide has some hidden feature tips like - Factory Default (Hold + and - ) - which I had to use once when the 0V Line Alignment (Hold Sel for 2 secs when ms is selected) completely messed up.
However my scope seems to add a little offset - a 0V reads as 0.6v - quite a lot of error of an offset.
That 9v power bank might have overshot the voltage when ramping 3.7v to 9v. There is prob not protection on the board to stop it. A short 15v overshoot will kill the microcontroller, or at least pieces of it.
Sorry forgot to mention. I found the switches were rather badly contaminated, (guessing oil). So it's just possible you have a bad solder joint. I'd definitely be checking your switches. Run over them again with your soldering iron and maybe check with some good magnification. After soldering in the first switch and finding it reluctant to take solder I went over the rest with a small strip of fine wet and dry and used some flux paste. A fiddly job but well worth the effort..
I finished mine this afternoon and it worked first up. A little bit of tweaking and it's working well. Not exactly the most complicated kit I've tackled, but I definitely needed a little magnification checking those tiny resistors. An excellent kit for $19.50 USD. I was impressed with the display, good resolution for the size. The inbuilt oscillator is a handy thing to have as well. I just wish someone had a suitable box to put it in, although it would mean remotely wiring all those buttons and switches. I was thinking of buying another kit specifically for for that purpose rather than trying to de-solder all those connections.
i recently bought one of the upgraded kits (13803k) and after building it it works perfectly, it has a little noise but within tolerance for a kit of such a price. i did all the soldering without using static protection (i did touch an earthed source before hand) and had no problems after. i think this is that 1 in 1000 chance to have a defective part that is with everything from tvs to mobile phones
I had a SMB version of this kit, and got it working fine. It is a great little project. I agree with some of the others here, 9V does not seem to cut it as a power supply, but 12V is solid.
I just got one of these pre-assembled for $15CAD. I'm pretty happy with it for the price. Wanna get an actual kit and build one once I get a better soldering iron.
Bought the same unit from Banggood and mine did the same exact thing. Now that makes me wonder if they are just faulty display screens.
I was thinking of getting one of these so I watched with interest when you reviewed it. Think I will now wait and see what transpires!!
I have found in the past a number of kits from China just use very basic manufacturers data sheets and exclude the extras that make it a safe working product. I guess that's the difference between a cheap kit and a named manufactured product.
It looks like the kits that are being offered now on Amazon are limited to soldering the mechanical parts and all the surface mount components are already installed.
+eTechTom Service mount? And you call yourself eTechTom?
Good catch. Of course I meant surface mount.
eTechTom :P I should damn well hope so
I had the same "mysterious" problem when I built mine. Several minor problems corrected (SMT resistors not completely soldered) but still nothing worked.. I decided to reflash the program and that fixed the problem. There are two versions of the program on the Banggood site. I am running the modified version that gives numeric details about the wave form... Very clever.
This oscilloscope was my third soldering project (after a little 16-LED blinking heart and a simple digital clock) and it instantly worked. Ok - I have to admit that it took me 6 hours, I followed the instructions and i measured all the parts before placing them.
I start getting the suspicion that the instruction to measure the resistors is not just there for raising multimeter sales. ;D
Bottom line: It's sad that this great kit may get a bad reputation because of someone who seems like a professional but is not able to follow a simple, linear manual.
I think it's highly unlikely that you killed the LCD, it looks to me like it is just not getting any display signals, and the missing -V supply probably has something to do with it, or is a symptom of whatever's causing the malfunction.
You could try replacing the LM7905 regulator and see if that gets the -V supply working again, and maybe the transistor that's part of the -V supply circuitry as well, hope that helps.
Built one, works a treat..... BUT obey the instructions and check every single resistor before soldering, I had 3 wrong values!!
It's very likely that ESD damage due to static from that suspiciously inadequate looking anti-static packaging (and/or careless handling we cringed at in the first video?) was the likely cause of the LCD (or its tiny driver circuit) failure. While it is possible this can be proved though very expensive investigation (requires an electron microscope and opening up the IC in the lab), the MFR should just replace it at no cost. Sometime a static discharge will just cause a glitch that requires software re-boot, but it's still a very good idea to take care because ESD damage can take several months to cause a failure if a very tiny hole (that gets punched by a very tiny spark) allows oxygen to enter, contaminate and eventually destroy the semiconductor layer/junction. BTW, back in the early days of 4000a/ae series C-MOS before internal protection design improvements, that was called “making the chip pregnant”! Use a wrist strap or better yet IMO, be meticulous in discharge/handling procedures.
Y'all blokes are all wrong. The problem is a fat electron that is stuck between two pins. That is a common failure with this particular model :)
A. R. Jasso I've had this issue before, I never use the stock electrons. Poorly machined crap. I only import hand made finely ground electrons from Canuckistan.
What's an electron in terms of components?
it was a joke.
Is it just me or at 8:28 what I presume to be the ribbon cable to the screen looks pulled away at the top? Before and after this, it seems to be flush to the screen.
How clean is the output of your powerbank? The reason I ask is that I have a few microcontroller boards that refuse to work with one of my banggood powerbanks despite its output voltage looking ok on a meter. When I checked the supply on the scope there was a ton of noise on there causing all sorts of hang-ups and weird behaviour (the board, not me).
I would test this again with a known clean linear PSU when you replace the screen just in case.........
Ronan Cantwell I'll try it on a 9v battery next time.
Ahhhhh.... Old school. 😁
what a shame
Proyectos LED Very frustrating! Took nearly 3 hours to build and now I can't do anything with it!
Julian Ilett been there done that!! especially with kits!
So did you end up figuring it out or just abandoned it as "not worth it"?
There's a follow up vid.
I had the same proplem couple of weeks ago!
I switched the tft Display with another one i had laying around and then everything works:)
Scavengerx3 Lucky you had another display (same type) lying around!
Julian Ilett yep have a lot of them :D
Around 10-15 pieces and one of those was this one i needed with the oscilloscope!
Maybe write an email to bangood and they send you a new display! :)
A years ago, i tried these kinds of TFT and parallel them with the same parallel bus, which turns out if the flux is too much between the data bus pin, it actually shorted out the signal with such high frequency clock and data. Try probe the pin with a multimeter and see whether they have any short may tell the internal TFT driver is damage or not.
Measure the resistances, capacitors and inductors twice before placing them, some of the resistors shipped were way off, some were off by a factor of 10 (so i'm guessing they misread the last band) so i had to use my own resistors. I imagine that had something to do with it.
Julian Ilett Hmm did you only check for the pulse-train on the -av point? It would seem to me that that is the regulated output of the 7905. Try and see if you can find the pulstrain on the first mentioned resistor, from the back side.
Just a guess: I had an issue with this kind of displays, with multiple ones, powering the backlight straight from 5V or 3.3V supply the display just turned white, and at first I thought I was getting faulty displays. The problem seemed to be with the backlight, because once I used a pwm output from the microcontroller and could regulate voltage supplied to the backlight (or used a voltage divider), at certain point the display would return to normal operation. I did not investigate the exact cause of this, but it seemed that once a high enough voltage was applied, the backlight interfered with the pixels on the display turning everything maximum white. It could also be the current issue, maybe someone can confirm this.
Have they help you solve the issue with the screen? When you start this series again, could I suggest a few things I would like to see to make it complete. You could ask them while you are trying to get it fixed if they could send you the update firmware. I have 45 and they are suppose to be up to 49(50 but they changed r11 resistor and firmware and will not give out firmware 50) but only 36 and 40 on the manufacturer site. You might want to show how to do the update, and tell us where we can get the later them 40 update. You might want to ask them about the new 138 with the 50 firmware that is suppose to have less noise and maybe they would want to send one to you to show the difference? Just some suggestions. Hope they get yours sorted out.
Thanks again for the videos.
Hello Julian.
I bought also that dso138 and an acrylic case.
If the dso boots, all voltages are ok but the screen is white blank, then, i had the same problem, i look for the test modus and later for the lcd/tft display. The display reacts on the slightest touch and goes white blank. I disconnected the display from its back lime and lift it a bit, so mechanical tensions are smaller to the flat cable.. Now it runs ok. I will not send it back, because i believe, there may come the same sh... back.
So not our foult.
I hate these blue resistors, when they over heat its impossible to read its values
Well I could not wait even though yours did not work. You must have done Banggood some good as I ordered mine and everything is coming except the scope kit! They must have sold out. I have it coming so that when you get yours working, I can follow along with whatever you do with it.
Thanks again and I hope you get yours fixed soon!!!!!!
Hi Julian, could it be that the failure of the minus voltage has somehow disabled the output from the ARM uP? Looking forwards to the next video. Kind Regards Bob
I think the display is fine maybe a few ports from the microcontroller got damaged for some reason. Is a 320x240 display see my last videos where I use a quite similar one for my new Solar BMS project. Mine is just the SPI version not the parallel one so less pins.
You can try to unglued the PCB from the motherboard and look at the flat flex soldering. With so many pins for parallel maybe one of them had a bad solder joint.
***** I just re-made all the solder joints between the flat flex and the red PCB (underneath the LCD panel), but it's no different. If the LCD problem is damaged ports on the MCU, that would mean the 2 faults are actually just 1 - damaged MCU ports - it makes sense. But is the MCU really so fragile?
Julian Ilett Maybe your Batterybank overshot the voltage while boosting. I didn't think my 5V Atmel 328P/PU was so fragile but apparently 5.9V Managed to kill it dead.
I guess it's to be expected when they're so damn complex.
Hope you get it fixed up soon!
Julian Ilett Is enough for just one pin not to be soldered correctly on the microcontroller to not initialize the 16bit parallel LCD. I'm getting it has something to do with their external circuit and those power supplies for it. Maybe one of few of the ports got over 3.3V and damaged the internal protection diode of the port.
The ESD was sure not a problem. I never cared about that and never had a IC of any type die because of that.
And you climate is much more humid so chances of ESD are even more reduced.
Look with a magnifying glass at the microcontroller pins. Maybe they send another unit. The LCD's are nice maybe you get a few (I think about 6 or 7$ for the 2.2" SPI ones with PCB on eBay based on ILI9341 controller) hey are quite nice do to high resolution. The parallel one require to many pins for the microcontroller.
There are larger displays 2.4" 2.8" and I think even 3.2" all based on the ILI9341 but also all have the same 320x240 resolution this are realy popular at the moment a sort of replacement for the Nokia 5110
Julian Ilett
The MCU is a STM32F103C8, almost the same as on a Naze32 (STM32F103CB) flight controller for example. While I have heard of people frying their FC board, it seems rare. And since the board is not only used by "electronic guys", but most often by people who just barely manage to solder, you could even say the MCU is quite sturdy. It has pretty much the same preotection measures in place as an AVR on an Arduino has and they don't fry that often either.
My guess is still that the MCU is failing on initialization of the display (which seems to come before the negative voltage clock is initialized).
It's that connector you soldered on upside down. As Dave Jones would tell you, , all the electrons fell out! 😄
Julian !! In this cell phone dominated world - Where did you get that great selectable multi-voltage power bank?? I have searched everywhere - and can only find 5V / 9V auto-select units for charging cell phones. And the 5 volt version I have automatically turns off on low current applications (thinking the "charging" is completed). I'd love a 9 volt portable - battery powered - rechargable power supply like that !! Thanks for all you do !!!
Sadly it's no longer available :(
A couple of thoughts, perhaps you should consider taking some ESD precautions ( feet in a bucket of water type of thing) when assembling circuits. Living room carpets can be killers and those green cutting mats are no help.
And yes a temperature controlled iron would help. It's not so much the temperature control but the higher power (eg. 50W) that makes them better. The temperature control just prevents the higher power from overheating the circuit.
number 33 This kit was a real pig to solder, I've never had this much trouble before. I think the spokes on the grounded pads are too thick and too short, but that may be just me making excuses. Looks like I've been beaten into temperature-controlled iron submission!
My ESD precautions are instinctive - touch something grounded before handling parts. But I suppose I should be SEEN to be taking the proper precautions. Maybe it's time to retire the cutting mat and get an ESD mat.
Julian Ilett On the subject of ESD precautions, here's a brilliant product, an anti-static wrist strap that's not only digital but wireless too. tinyurl.com/neecsxj Yes, I was googling "Anti-static matting", and it's expensive stuff. Surely there must be something that's naturally slightly conductive that would be cheaper like for instance black craft paper or maybe black bin-bags. Trouble is it's so difficult to measure such low levels of conductivity.
number 33 sit in the bath, fill with water, both remove static and enjoy at the same time! :}
jusb1066 Hmm, I like it. Probably wouldn't use my mains powered soldering iron in the bath though.
number 33 No offence but you must be joking. A wireless ESD Band? The whole point is it has a 9M Ohm WIRE going to ground... I don't see how having something electronically floating in the breeze will help at all
I ordered the pre-build one with the SMD already soldered. Therefore only 500 other parts needs to be soldered.... Anyhow. Mine works fine and have a lot of fun.
Double check J4 has been bridged as well, I had to do it a few times to get a solid connection.
Maybe a loose connection between the TFT panel and the board underneath.
Make sure youre using a center positive power source. mine did this until i changes from a center negative power source to a center positive. A 9volt battery would also work
Have you had any luck getting it running or in getting banggood to send another scope or screen? I was hoping you would show us things we could or can do with it in our hobby.
Good luck.
amtpdb1 I've fixed the missing negative analogue voltage (AV-). That was due to resistors fitted in the wrong locations - 120 ohms in horrible 4-band colour code reads the exact reverse of 10k :(
I've asked Banggood for a new LCD - waiting for a reply.
Julian Ilett Thanks for getting back so quickly. It's hard to beleave that they are taking so long to get this resolved considering that they sent it to you for a review! You would have thought they would have just sent you another kit just so you would say how efficient they were to resolve issues!
Have a nice weekend. But I am still waiting for you to show me how to use it!!!!!! (:-}
Julian Ilett Are there any updates on the replacement screen?
+Julian Ilett i soooo would have bought and built one of these if it had have worked for you. i'm still keen to see one working. Maybe if they don't send you the replacement (or new display) you can do a hammer destruction video of it - you might make enough cash from views to buy a replacement.
+chillzwinter I built the first model they had and then purchased the second model that they came out with that has better noise elimination. The manufacturer finally gave out the better software, so I will change both to the new software. I had a couple of problems. I had to change out a voltage regulator as I was getting the wrong voltage, and remove one chip and re-soldered it Jye does get back to you on their forum to resolve issues. One thing is that you need to get a 9 volt power supply as if you use a battery as most start off with, when the voltage drops everything goes haywire.
Good luck
You need to buy the LCR component tester kit first ;-)
Let see the next episode !
I really enjoy your videos Julian, including this one, but I'm always surprised by your lack of a current limited bench power supply! It's too easy to make a mistake when "building up" any PCB. Watch this space. (Well, your space).
What is the formula for the remote circuit board.
Did you ever get this running?
Hi.
Have you sorted this out yet?
I believe that the instructions were a little unclear on JP4 having to be shorted out or it causes the display to not work properly.
Please share the schematic. Thanks
encodersofia That should now be at: drive.google.com/open?id=0B2WOCQwdjgf3RzFEUnZvbnBiTkU&authuser=0
I've got a trace but if I touch the leads I get nothing on the screen or if I connect the red lead to test signal. What could be my problem?
I had the same problem. I couldn't figure out why I was getting that blank screen. It turned out to be a improperly soldered pin.
So I tried a third one after a few minutes of use the screen just goes white. The 2nd one came back to life once but then turned white a few minutes after I used it. Not worth anything.
I had a similar problem with my LCD except mine never showed an image only displad white screen. The instruction stated that R36 should be checked. I checked it and it read 180 ohms replaced it and still wouldn't work. I decided to replace the resistor but only had a 220 ohm. I solder it in anyway and the display started working. Haven't had any problems after a couple of hours of use.
Mine blew up when I set it down on a wire. The other I built was junk.
Just built mines today, I also have 0.687 V on the AV- However I have a working display and a trace. But the trace is either on the bottom of the screen or the top of the screen. Frustrating indeed. You can try to reflash the chip, it might just be a bug. One of the 16v 100uF capacitors actually went short circuit, I pull it out and replaced it with a 25v 100uF.
Oh and I found out that this scope is very picky about input voltages and current. It wasn't happen when I fed it 9.00V at 500ma. It was screaming and making music. I changed the voltage to 9.39v and 1.00 A. No more noise and it worked just "fine". I used a KORAD Linear PS that I bought for $40.
Walter Boxhead JP3 JP4 are both shorted. JP3 connects the two ground together, and JP4 supplies power to the MCU. I thought it was the transistor, so i took it off the board and the transistor is fine. I'm getting 1.2v out of VGEN. I dont have another scope to help out.
You might want to test all the GND points on both the LCD and discrete components , like mentioned you did say you were having problems soldering them.
For those sort of kits a good temperature controlled solder station is a mist, maybe look at getting one of the many Haiko clones on aliexpress?
At my first power on the display is white blank and the Green LED is steady it does not blink at all. What could be the problem?
the 79L05 is on U4 and the 78L05 on U5
Could you add in the video the schematic. I have it but parts of the schematic end with digital grounds. You could tell us what the difference is between the different grounds and anything else you might see to help the beginners.
Thanks again.
Good evening Julian.
I'd like you to ask Banggood about the display. Does he sell it separately I wonder? What is the resolution? Looks like a parallel (high speed?) interface.
any luck with the dso? i have the same issue...
You know it is probably a stupid suggestion, but when all else fails I always try plugging in the USB cable to see if that jolts anything into action.
Can jou try de USB connector? And try to read out de data?
Might it be a short circuit between the jumper pins beneath the display, and the display?
p.s. Love your videos.
How do you separate the inductors from the resistors
They're a bit bigger and fatter - and your component tester will show them as inductors.
Julian Ilett any testers you would suggest?
Note , they have changed a resistor value which is not mentioned in the main assembly instructions, just on an extra bit of paper shoved in! Get it wrong and the sensitivity is very poor!Mine worked first time, luckily!
I also built one ,works perfectly for me
Is it worth trying to flash the later firmware to see if that is accepted? That'll show the microcontroller is working. It's a bit like it's failing to fully boot and initialise the screen.
Steve Cooper That would be worth a try - there's a link to a reflashing procedure document on jyetech's website. MrOpenGL supplied the address: www.jyetech.com/Products/LcdScope/e138.php
Check all your solder joints, had the same problem. Turned out to be a dry join on the lcd connector pins. Also there are two points that need shorting with solder, jp3 and jp4. Good luck and clean your iron 😜
i have purchased this kit and would like a link to the schematic if possible. i haven't started to assemble it yet.
My first one went up in a puff of smoke. I had to replace all three power regulators to get it running. Not sure if my board is the older type or not, and I'm also not sure if it need to be modified by linking the capacitors together or not? How can I tell?
[IF YOU DON'T WANT TO READ, THE SOLUTION IS THE SECOND LAST SENTENCE]I don't know if it really matters anymore, but I found the solution. I've had the same problem with my unit(led flashing correctly, screen not working), and after 1 year of sitting on the shelf, i found it while organizing, and decided to give troubleshooting a shot. I went about troubleshooting it as shown in the manual, and it turned on! For at least a little time. I found that if you fiddle around with the screen, bending it back and forth, it sometimes worked, and sometimes didn't. So I pulled the LCD with its metal casing and it was sitting directly on the top of the solder joints of the ribbon cable -.- . So I just stuck a bit of kapton tape on the solder joints, put the display back on with a bit of glue(as I had destroyed the double sided sticky tape by removing it), gave it power, and that solved the problem for real this time. Hope it helps somebody that is struggling with this issue.
That always feels good pulling off a nice fix like that.
Definitely
just out of despair, because I had the same problem, I took off the metal plate, I removed the flexive tape from connections, and voila, it worked, thanks ...
If your having problems with the TFT display check & resolder the TFT header on the TFT and the main PCB. I let my mate solder it as he was eager to do it but found the display wasn't working & after checking with ohm meter found dry joints.
Does the power supply spike when switched?
Thanks you for Video. My DSO 138 White screen and no booting. Help.
Same here!
the DSO112A made by the same company is fucking excellent. it has very high build quality & is rather surprisingly sharp. comes with a built in lithium ion battery. i designed a 3D printable chassis for it that holds two 18650 batteries in parallel so it lasts forever. jyetech.com/dso-coral-112a-oscilloscope/ www.thingiverse.com/thing:4047330
Similar problem to me, and voltage verification doesn't work in the same Pins you revissed. Furthermore ...I did see some board in youtube and publicity with pre-soldering Micro resistenses and Chips... Unfortunately, my recived kit wasn't soldered this part
My kit arrived but I have not built it yet... every now and then I look at it with all those little SMD parts... and decide to do something else instead :) Hopefully I'll have better luck when I eventually get around to it. btw do you know what the UART connection lets you do?
***** Yes, I'd be interested to hear whether you have any trouble with yours. It seems you use the UART connection to upgrade the firmware - details here: www.jyetech.com/Products/LcdScope/DSO138_oscilloscope_upgrade.pdf
Julian Ilett Blank white screen. All symptoms same as yours except I never saw the proper screen ever, and no amount of fiddling with the switches will make the LED blink again after booting. Interestingly, I do get the correct AV- voltage of -5V when the screen is attached though (and 0.6V when screen not attached). I always did have a feeling I would be flushing 3 hours down the toilet, but for $20 it was worth a try.
***** I'm surprised - I thought it was just bad luck that my scope didn't work. I'm also hugely disappointed - the scope looks really useful... if the display worked! I've contacted Banggood - they said they'd pass the info onto their tech people. It'll be interesting to hear the response.
***** Hmm, that's interesting - I don't think mine does that, but I'll have another look. I really can't decide if it's the MCU or the LCD that's failed. The additional problem of no -ve voltage pulses makes me suspect the MCU more than the LCD, but I have no idea why it worked for 2 minutes then turned its toes up. Your video looks like some control signals are getting into the LCD though. A replacement kit would help me resolve this, but Banggood have so far only suggested using a different power source (which I'll try of course). I'm sure if I nag them, they'll send another kit!
Ive resolved any issues ive had with the parts and the construction of my kit is complete and is running without issues , Calibrating it is a bit fun tho
Banggood is NOT JYEtech, and the firmware is different.
I have an updated kit coming now. It has the 050 firmware.
I have the same one, and I'm not getting the trace I think it has something to do with the PNP transistor q1 below the choke.
Likely that you over volted the screen, sometimes in cheap devices the power for the screen is taken from the input before the voltage control for the MCU. I'm guessing the justification for that would be bc its draws more powe prhaps? The MCU isnt getting feedback from the screen so its not going to initalise the clocks needed for measurement. The test signal is likly to be using a hardware timer and interupt so the MCU wouldnt need to be fully booted up for it to give the signal. I would try plugging that screen into an arduino and running some example programs or piggyback a known good screen onto the board. That way you will know if you over volted the screen or the MCU.
Hi
I have exactly the same fault, I think they use a replacement lcd with a different initialisation routine. I hope you find the problem or Bangood opens the firmware so I can debug it.
What you want to do is buy yourself a good strong magnifying loupe and use it to give each solder-joint a good close eyeball and check that they are all good, and there are no unintentional short-circuits, or solder-bridges, or dry solder-joints, I've got to the point where I always use a good temperature controlled soldering station whenever I do any soldering now, I'm looking at buying one of these Digital Scope kits from Banggood soon, it will be going in a big analog Modular Synthesizer which I'm in the process of building.
Just built one of these from Ebay and, much to my surprise, it worked at first power-up, the only snag is that the probe compensation capacitor on the 1 volt range doesn't seem to do anything. Any idea as to the use of the USB connector?
backward Schottky diode?