I came to your channel as I was looking at Elekit videos in preparation to doing my own TU 8200. Really impressed by your systematic approach and incredible patience to even re solder all the connections! Great work.
I will only say 1 thing about elekit. They are top quality but if you are in North America i would suggest that you purchase them from an authorized dealer that has bought them from the official distributor for north america, vkmusic. I met the distributor when I had to get the part for this one. This particular amp was a grey market import, which sold for less than he can bring them in for. This has him pissed off to the point that he is ready to throw in the towel and say "fuc* it" and if that happens there will be no support. He even had the manuals all translated to English for us to assemble. If he quits, we will have to learn to read japanese. Elekit vacuum tube amps are probably the finest tube amp kits you can buy. 10 out of 10. I have built 2, and am considering a 3rd.
Thanks Dave, pretty slick the way you do step by step diagnoses and get to the "bad news". Now the ball - part is in their hand. Glad you shared the tutoring. J K
I find it funny when people make comments like "This thing isn't worth what people are asking" and then get put in their place by comments from others, including me. I think mine was "Is it too much for the equipment or too much for you?" Anyway, these trolls always wanting to get the last word in make an other comment and then delete their post. Thing is I get the notifications, and today I feel that everyone should see the deleted post. (name deleted) 12voltvids My main interest over about 30 years is electronics. I have bought a lot on Ebay and know what you get for the money! I like that things are of a certain quality and not just rubbish! And I know when something is overpriced! Again, it is too much for the item, or too much for you? Just because YOU won't pay the price, doesn't mean that someone else with more disposable income will. Who are you to say what something is worth? Ever heard of a free market? No you are one of these people that has a little fit about prices and has to whine and complain about it. Don't like the asking price, nobody is holding a gun to your head forcing you to buy it. Someone with more money than you will buy it at the asking price if they want it bad enough. I sold a betamax for 700.00 that I got for free. Does that make me a bad person? I didn't force the buyer to pay that. I put it on Ebay hoping to get 100, and it ran away because someone really wanted it bad and they got it. For that matter, I sold a single disk CD player, that I got for free to a vintage stereo store. The guy game out and started handing me 100 bills. 500.00 for something that cost me nothing and I wouldn't have paid more than 100 for it, but he turned around and sold it within a week for 600.00 (it was an SLP50 that I really should have kept as it was a fantastic unit, but 500 in hand won out) When I worked in the retail shop, we sold very high end products, had a 24,000 TV in there at one time. We would get the odd tier kicker in that would whine and complain about the prices of the elite and ES series equipment. The salesman's response to every one of them was as you probably guessed... "It is too much for the product or too much for you?" They generally left a bit red in the face as there is really no come back to that comment. That ends it all in embarrassment. I guess it was because the comment was deleted by the poster.
I read that comment while posting mines, don*t feed the Trolls Sir ..... ~80.000 + Subs should always tell You: Hey, some People like what I do and how I do....
I've read all this comment through a few times and am probably missing the point that you're all trying to make about the deleted post and getting upset about. Stuff IS over priced a lot of the time and not a reflection of its intrinsic value. If one buys it at that high price then one of a few things can be assumed. You have NO idea the value, you DO have an idea it's vastly overpriced but have enough income just not to care and/or a combination of all those things. Example: There is a product that keeps popping up on Facebook recently that is nothing more than a colour changing corner light. I've seen it advertised from $7 to $120 for the same thing. True. On the higher price adverts there are naive comments such as 'I like it but it seems expensive, what do you folks think'. That's an understatement to say the least as it IS a $7 item. If the person making that comment goes on to buy the product then I think we all know they've been ripped off. So, if I walked into a store and saw that product at that high price, made a comment to that effect and the store reply was 'is the item overpriced or is it that you just can't afford it' I'd probably break the guy's face. A lot of 'tube' based audio is vastly overpriced because the maker's are creaming off everyone's brainwashing into thinking there is some kind of incredible magic going on that justifies the price. I have some NOS Mullards I have owned for years that are currently selling at silly prices on ebay. I also have some regular new JJ valves bought recently at a fraction of the cost. I CANNOT tell the difference in sound between them. If I walked into a store to buy valves and was offered NOS Mullards at the price I've seen them, refused and then the comment was made 'are you saying they are too expensive for you' then you guessed it, I'd break the guy's face. We all clear now? I don't know the cost of that 2 tube thing you repaired but if it is overpriced then whoever made the comment and deleted it should have been given a better break. Why? Because he's probably fucking right and has a right to comment. This is a comments section last time I looked.
Though I used it today for an SMD repair, I have never liked using copper braid for repair work. Most repairs go much faster and with much less heat damage with a good electric desoldering pump like the Hakko FR-301. Especially useful on PCB and point-to-point repairs. Only wish they were an affordable alternative to the braid and the ubiquitous solder-sucker 40 years ago when I started out in this business.
Dave, you mentioned that this unit came without the power supply. It looks like a standard 12vdc wall wart. You can up these online for ridiculous prices, but a better idea is to check out your local Goodwill or similar (when they reopen) where they probably have a barrel of them for around a buck. I volunteer in a small nonprofit shop associated with a senior center, and we have, no exaggeration, 100’s of these things and are looking for ways to get rid of them.
The Power Supply of this Amp is not a Cheap low Q 5,99 somethin Walwart, its a very decent Brick puttin out 5 Amps @ 12V . 60W+ Walwarts, no dice here? Dave uses the Power Supply of his TU8100, the customer has also said sorry for not sendin the PS in a (deleted) comment
The owner didn't send psu to save weight and shipping costs. I have the correct smps as I have the same amp. Mine has probably 1000+ hours of pure musical enjoyment on it. These make killer headphone amps.
I thought about building one of the Japanese kits, not this one. Quite complicated for 2W per ch., I mean the power supply section. Watch smoke blow... Damn, very confusing little POS, programmable chip to drive HV power supply. Yeah, I would rather see regular transformer and normal PS, but this days everything is cute and small, running of 12V or laptop power supply. It should drive higher impedance headphones like Sennheiser HD600, 650, Beyer DT880, 990 or similar ones nicely ones fixed. Or large high efficiency horn spkrs. Waiting for part 2 of the mystery.
Controlling Currents and other "relevant" States to run that or any Tube Amp is not the baddest thing today. Sure, a "propietary" programmed CPU to protect the Hardware and Your Speakers, even Your "Life"... a slightly bad Taste... And for Headphones there are very good Tube Amps...Japanese/Chinese and even Big Names like Marantz, Fisher, Sennheiser, Stax etc. have pristine Headphone (Tube) Amps....
@@LittleGizzmo This is probably the best sounding headphone amp you will find at any price. Too bad it doesn't have a headphone jack, but easy enough to connect. The TU8200, which is the 3 or 8 watt version depending how you set the jumpers (triode, pentode or UL) does have headphone jack and I use it all the time with cans. The bigger TU8200 uses a conventional torroidal for HV, but still uses semiconductors in the tube bias circuit, which is a good thing, as they can very accurately monitor tube current and make minute adjustments to keep the tubes running correctly throughout their life, and actually greatly extend the life of the tubes. All these ELEkit amps are critically acclaimed amps and are in many audiophiles systems. They sound that good! They are expensive though, and you have to build them youself. I am in the waiting list for another one which will cost me even more and provide a few days of building enjoyment once it lands here. Unfortunately myself and many others are waiting for new stock of kits.
Well that is how they do it on this one. The big brother uses a toriodal transformer but still uses solid state devices to set the bias voltage which is far more accurate than a manual control.
But that is an issue with anything you buy or own. As long as these NOS tubes are available I don't see them discontinuing the kit, and once they do, all they need to do is make the code available for the PIC so someone wanting to fix can just burn a blank chip.
@hvacr tech You can download the code from PICs, but quite sure they set it into read protect mode, so you can't. They don't want to give it away for making knock-offs. But as Dave said, they will do the right thing if they make the .bin file available when they decide to discontinue the kit. I very much doubt they will, but let's hope. And if they don't, someone with good PIC programming skills can write a new code for it. Though I don't like the concept they used a programmable device here. They develop 'amnesia' after a few decades. So these amps will probably be unrepairable within 40...70 years :-) , even if they finally publish the bin file, because who will have the file after many decades. It would be nicer if they used a TL494 for the PSU, an LM324 for sense amp with uA339 comparator, and a few 555 for timing. That would be super repairable. It sounds like a lot of chips, and probably that's why they decided to use a PIC, but if they made this PSU/controller circuit on a vertical daughter board with SMD components (pre-assembled for those who don't like doing SMD), it would fit into this small case, and could be repaired by anyone with good troubleshooting skills in electronics.
Presumably, the PIC monitors the current and voltage on the tubes via resistor dividers? Are the resistors of the correct value? Excuse us lot standing and shouting from the touchlines! Enjoyable video.
Dam what a shame, i would be really upset if it didnt work after assembly :-( I could not see your diagram clearly but are the gate biasing resistors both ok?
Since the PIC monitors multiple points in the circuit, it's too bad it wasn't programmed to flash out a trouble code using the LEDs when it goes into shutdown mode. That way at least you'd know which input triggered the shutdown.
It actually does. If a fault condition is caused by over or under voltage or over current on a tube that led will flash. If it is something that is detected on both tubes then both flash. In this case there was drive missing to one mosfet and thus the voltage was low to both tubes. This is a fault that should never happen, according to the designer, whom I was in contact with via the distributor for north america.
Interesting that it's using PCL86, that valve I've only seen as the audio output in televisions. P series valves were intended for series connected heaters, commonly used in TVs, rather than parallel connected 6.3V heaters, like the ECL86.
PCL86 was designed for TV! This is probably why they designed thius amp like this. I am sure there was a huge inventory of PCL86 (14GW8) and ECL86 (6GW8) tubes kicking around. Of course the PCL japanese version used 14v heater, and the American version 6GW8 used 6V, and that is why the jumper inside, so if the 14v tubes go out they can be replaced with 6v versions.
Interesting how it is a hybrid amp, where it uses tubes but has a solid state power supply and safety circuit, and how the B+ supply is derivied from the lower voltage of the wall-wart.
It is not a hybrid amp. The solid state components are not in the audio circuit. It could very easily be mains powered with a conventional transformer. The design was to use an inverter in the power supply as a safety precaution so everything can be monitored for any faults. A hybrid amp would be a solid state power amp with tubes in the audio path, such as a luxman lv103 or 105
Would you be able to take the signal from the working signal output of the IC and connect it to the fet that doesn't get one? the timing wouldnt be right, but at least the fet that does get the signal wouldn't go into compensation mode.
Was my 1st thought too, just try the functioning Pin with Signal and "bridge" it to the FET that gets the "bad" Signal, I looked at the Schematic, and even a small Signal from the "other" Out is send to the Fet through some Resistors and Caps around them FETs....
Sure and the voltage from the output of the transformer would drop to 0. They switch back and forth out of phase to create a N-S-N-S polarity on the transformer. The output like thin ^v^v^v^v which is full wave rectified. With only 1 output working it is more like this ^ ^ ^. Half wave basically.
@@12voltvids So both Fets would work on the positive swing only and might create another overvoltage situation, since the both work on the same pulse. You need a signal delay that shifts one signal to the "off" time of the original signal. or a new IC *lol*
@@Asriazh You did see the pulse width change when it fired up right. This is how it regulates the voltage. A sample from the DC is fed back and measured which changes the duty cycle of the fets to control the output voltage of the transformer.
I'm kind of glad that all of the amps I've made don't include "smart" features. I wonder if the original assembler "cooked" the IC while installing it. I really prefer to socket IC's on PC boards.
You should try one of the modern designs with the auto biasing. They really sound great and don't require re-biasing through the life of the tube, plus you can roll tubes any time you choose and the new ones will sound perfect from first installation. This plus automatic bias through the life of the tube means no sound changes throughout the working life. I have both, and the modern self bias is superior. Incidentally this amp is not such. The TU8200 is though.
Question, my tube headphone amp is a Little Dot Mark VI. Balanced output. I habe multiple sets of tubes. Very knowledgeable in electronics, but I dont know tubes..lol. What I do know os they are unbeatable sound. I am having a problem where one channel drops out at low volumes. You habe to crank the volume rapidly to "awaken" the dead channel. Bias currents are correct. Anything known with tubes that could cause this? Not a mechanical issue. It can fo days without problem. Other times it wont work long enough to listen to one song. Is this something you could diagnose as my time to learn tube topology is limited. My company ships electronic gear worldwide, so unless it falls out of the plane at 30,000 ft, it will get to you safely and you would reuse the custom packing blocks and box to get it back to me.
This new youtube I cant see what I am typing. So fristrating. So ignore the typos as I cannot see until I publish. I have two sets of tubes. No difference. No microphones with my Tungsol tube set, but still drops out. Bias current is stable for all 4 output (balamced). I suspect one of the 4 channels is dropping out.
The design of this bothers me a little bit. they are driving ordinary MOSFETs from a microcontroller directly with no gate driver. this is a seriously BAD idea in more ways than one. They could have went at least with logic-level FETs. it would be less taxing on the microcontroller, and it would be able to drive it into full saturation a bit better. So I wonder if the design flaw caused the PIC to fail. it may not have the drive current for those FETs, or just barely. Back when I experimented with a microcontroller based SMPS, I had to use a gate driver. I had issues otherwise.
This is a 2sk4017 which is a logic level mosfet. 4v will drive the fet into full saturation. it has a max gate voltage of 10v. Not the newest of designs but one that is stable and been around for a long time. No need for a gate driver with this, just a pull down resistor to turn it off when TTL drive voltage is removed. My unit has been running flawlessly for 3 years and it gets a fair bit of use.
I am not saying it doesn't work, I am just saying ive had bad experiences when designing/using circuits built like this. ive had troubles. I guess it all depends on switching frequency, currents, and parts selections I suppose. In this case, PICs are usually around 25mA Max drive current from any of the GPIO pins such as the PWM outputs used in this case. This is cutting it close.
Not about to put my amp at risk. These things are expensive. I think mine was about 400.00 by the time taxes were paid and the big brother to it was 1120.00 Thats serious money for a bag full of parts. I want to build the even bigger brother, but unfortunately there is a wait list of over a year to get that one. I have had my name on the list since it was announced and no email informing me that I can bring 2000+ for in and exchange it for a bag of parts and then another 600+ for a couple of vacuum bulbs.
@@12voltvids Well good for you. I've been an electronic bench tech for almost 40 years. Love your videos but is it really a good idea to teach this bad safety practice to others who are trying to learn?
Love your videos but this time I think you would have done better if you didn't use the diagram you would have figured it out better and faster using your Great electronic knowledge . Looks like your Diagram made it more difficult this time .
![Chino Pacas - Smith (ft. Junior H & Fuerza Regida) [Video Visualizador Oficial]](http://i.ytimg.com/vi/BVK6k56X30Y/mqdefault.jpg)
I came to your channel as I was looking at Elekit videos in preparation to doing my own TU 8200. Really impressed by your systematic approach and incredible patience to even re solder all the connections! Great work.
I will only say 1 thing about elekit. They are top quality but if you are in North America i would suggest that you purchase them from an authorized dealer that has bought them from the official distributor for north america, vkmusic. I met the distributor when I had to get the part for this one. This particular amp was a grey market import, which sold for less than he can bring them in for. This has him pissed off to the point that he is ready to throw in the towel and say "fuc* it" and if that happens there will be no support. He even had the manuals all translated to English for us to assemble. If he quits, we will have to learn to read japanese. Elekit vacuum tube amps are probably the finest tube amp kits you can buy. 10 out of 10. I have built 2, and am considering a 3rd.
@@12voltvids Thanks. I'm in Australia. Dealer here runs day long Amp camp on site.
Thanks Dave, pretty slick the way you do step by step diagnoses and get to the "bad news". Now the ball - part is in their hand. Glad you shared the tutoring. J K
I find it funny when people make comments like "This thing isn't worth what people are asking" and then get put in their place by comments from others, including me. I think mine was "Is it too much for the equipment or too much for you?"
Anyway, these trolls always wanting to get the last word in make an other comment and then delete their post. Thing is I get the notifications, and today I feel that everyone should see the deleted post.
(name deleted)
12voltvids My main interest over about 30 years is electronics. I have bought a lot on Ebay and know what you get for the money! I like that things are of a certain quality and not just rubbish! And I know when something is overpriced!
Again, it is too much for the item, or too much for you?
Just because YOU won't pay the price, doesn't mean that someone else with more disposable income will. Who are you to say what something is worth? Ever heard of a free market? No you are one of these people that has a little fit about prices and has to whine and complain about it.
Don't like the asking price, nobody is holding a gun to your head forcing you to buy it.
Someone with more money than you will buy it at the asking price if they want it bad enough.
I sold a betamax for 700.00 that I got for free. Does that make me a bad person? I didn't force the buyer to pay that. I put it on Ebay hoping to get 100, and it ran away because someone really wanted it bad and they got it.
For that matter, I sold a single disk CD player, that I got for free to a vintage stereo store. The guy game out and started handing me 100 bills. 500.00 for something that cost me nothing and I wouldn't have paid more than 100 for it, but he turned around and sold it within a week for 600.00 (it was an SLP50 that I really should have kept as it was a fantastic unit, but 500 in hand won out)
When I worked in the retail shop, we sold very high end products, had a 24,000 TV in there at one time.
We would get the odd tier kicker in that would whine and complain about the prices of the elite and ES series equipment. The salesman's response to every one of them was as you probably guessed... "It is too much for the product or too much for you?" They generally left a bit red in the face as there is really no come back to that comment. That ends it all in embarrassment.
I guess it was because the comment was deleted by the poster.
I read that comment while posting mines, don*t feed the Trolls Sir ..... ~80.000 + Subs should always tell You: Hey, some People like what I do and how I do....
@@LittleGizzmo very damn well said Sir.
you're letting trolls win by giving them air time.
I've read all this comment through a few times and am probably missing the point that you're all trying to make about the deleted post and getting upset about. Stuff IS over priced a lot of the time and not a reflection of its intrinsic value. If one buys it at that high price then one of a few things can be assumed. You have NO idea the value, you DO have an idea it's vastly overpriced but have enough income just not to care and/or a combination of all those things. Example: There is a product that keeps popping up on Facebook recently that is nothing more than a colour changing corner light. I've seen it advertised from $7 to $120 for the same thing. True. On the higher price adverts there are naive comments such as 'I like it but it seems expensive, what do you folks think'. That's an understatement to say the least as it IS a $7 item. If the person making that comment goes on to buy the product then I think we all know they've been ripped off. So, if I walked into a store and saw that product at that high price, made a comment to that effect and the store reply was 'is the item overpriced or is it that you just can't afford it' I'd probably break the guy's face. A lot of 'tube' based audio is vastly overpriced because the maker's are creaming off everyone's brainwashing into thinking there is some kind of incredible magic going on that justifies the price. I have some NOS Mullards I have owned for years that are currently selling at silly prices on ebay. I also have some regular new JJ valves bought recently at a fraction of the cost. I CANNOT tell the difference in sound between them. If I walked into a store to buy valves and was offered NOS Mullards at the price I've seen them, refused and then the comment was made 'are you saying they are too expensive for you' then you guessed it, I'd break the guy's face. We all clear now? I don't know the cost of that 2 tube thing you repaired but if it is overpriced then whoever made the comment and deleted it should have been given a better break. Why? Because he's probably fucking right and has a right to comment. This is a comments section last time I looked.
@@chillidogkev 👍
I love electronics .i love your videos you are one great technician thank you for your videos
Though I used it today for an SMD repair, I have never liked using copper braid for repair work. Most repairs go much faster and with much less heat damage with a good electric desoldering pump like the Hakko FR-301. Especially useful on PCB and point-to-point repairs. Only wish they were an affordable alternative to the braid and the ubiquitous solder-sucker 40 years ago when I started out in this business.
Nice explanations,great video thank you
Thanks for your troubleshooting videos
Thanks Dave, looking forward to part 2
Once I source a new pic
Like the video, troubleshooting helps solve coming issues
Dave, you mentioned that this unit came without the power supply. It looks like a standard 12vdc wall wart. You can up these online for ridiculous prices, but a better idea is to check out your local Goodwill or similar (when they reopen) where they probably have a barrel of them for around a buck. I volunteer in a small nonprofit shop associated with a senior center, and we have, no exaggeration, 100’s of these things and are looking for ways to get rid of them.
The Power Supply of this Amp is not a Cheap low Q 5,99 somethin Walwart, its a very decent Brick puttin out 5 Amps @ 12V . 60W+ Walwarts, no dice here? Dave uses the Power Supply of his TU8100, the customer has also said sorry for not sendin the PS in a (deleted) comment
The owner didn't send psu to save weight and shipping costs. I have the correct smps as I have the same amp. Mine has probably 1000+ hours of pure musical enjoyment on it. These make killer headphone amps.
that was one excellent video. loved it.
I thought about building one of the Japanese kits, not this one. Quite complicated for 2W per ch., I mean the power supply section.
Watch smoke blow... Damn, very confusing little POS, programmable chip to drive HV power supply. Yeah, I would rather see regular transformer and normal PS, but this days everything is cute and small, running of 12V or laptop power supply.
It should drive higher impedance headphones like Sennheiser HD600, 650, Beyer DT880, 990 or similar ones nicely ones fixed. Or large high efficiency horn spkrs. Waiting for part 2 of the mystery.
Controlling Currents and other "relevant" States to run that or any Tube Amp is not the baddest thing today. Sure, a "propietary" programmed CPU to protect the Hardware and Your Speakers, even Your "Life"... a slightly bad Taste... And for Headphones there are very good Tube Amps...Japanese/Chinese and even Big Names like Marantz, Fisher, Sennheiser, Stax etc. have pristine Headphone (Tube) Amps....
@@LittleGizzmo This is probably the best sounding headphone amp you will find at any price. Too bad it doesn't have a headphone jack, but easy enough to connect. The TU8200, which is the 3 or 8 watt version depending how you set the jumpers (triode, pentode or UL) does have headphone jack and I use it all the time with cans. The bigger TU8200 uses a conventional torroidal for HV, but still uses semiconductors in the tube bias circuit, which is a good thing, as they can very accurately monitor tube current and make minute adjustments to keep the tubes running correctly throughout their life, and actually greatly extend the life of the tubes. All these ELEkit amps are critically acclaimed amps and are in many audiophiles systems. They sound that good! They are expensive though, and you have to build them youself. I am in the waiting list for another one which will cost me even more and provide a few days of building enjoyment once it lands here. Unfortunately myself and many others are waiting for new stock of kits.
That is why I don't like those monitoring/protection circuits in a tube amp.
Without that shit the amp would run just fine.
All the best,
Robin
Not true. If your amp runs away the tubes, audio transformer and power transformer will burn up and this gets real expensive really quick.
@@12voltvids the fuse should blow first
A 300.00 transformer will protect a .10 fuse by blowing first.
As a general note, I use liquid RA flux on any board work. I also use a temperature controlled iron with separate check of temperature,
My iron is temperature controlled and has been calibrated.
@
mrnmrn1
I fully agree PIC's have no place in tube amps, nor have SMPS power supplies.
Well that is how they do it on this one. The big brother uses a toriodal transformer but still uses solid state devices to set the bias voltage which is far more accurate than a manual control.
Could be a problem in the future, when this amp is discontinued and if the programmed PIC is no longer available from the manufacturer in Japan.
But that is an issue with anything you buy or own. As long as these NOS tubes are available I don't see them discontinuing the kit, and once they do, all they need to do is make the code available for the PIC so someone wanting to fix can just burn a blank chip.
@hvacr tech Yes that is possible.
@hvacr tech You can download the code from PICs, but quite sure they set it into read protect mode, so you can't. They don't want to give it away for making knock-offs. But as Dave said, they will do the right thing if they make the .bin file available when they decide to discontinue the kit. I very much doubt they will, but let's hope. And if they don't, someone with good PIC programming skills can write a new code for it.
Though I don't like the concept they used a programmable device here. They develop 'amnesia' after a few decades. So these amps will probably be unrepairable within 40...70 years :-) , even if they finally publish the bin file, because who will have the file after many decades. It would be nicer if they used a TL494 for the PSU, an LM324 for sense amp with uA339 comparator, and a few 555 for timing. That would be super repairable.
It sounds like a lot of chips, and probably that's why they decided to use a PIC, but if they made this PSU/controller circuit on a vertical daughter board with SMD components (pre-assembled for those who don't like doing SMD), it would fit into this small case, and could be repaired by anyone with good troubleshooting skills in electronics.
When this is the reverse pulse signal, why not generate it from pin 15?
@@12voltvidsI don't know about Elekit. But the problem is some manufacturers don't make their proprietary PIC code available.
Presumably, the PIC monitors the current and voltage on the tubes via resistor dividers? Are the resistors of the correct value? Excuse us lot standing and shouting from the touchlines! Enjoyable video.
Yes monitors voltage and current. Yes resistors are correct value.
Are the tubes on the output stage, preamp or buffer? well since i see 2 output transformers I assume the tubes are finals.
They are dual tubes, a triode preamp and a pentode output.
Dam what a shame, i would be really upset if it didnt work after assembly :-(
I could not see your diagram clearly but are the gate biasing resistors both ok?
I checked the bias resistors and as you saw swapped the FETs to rule out FET.
Since the PIC monitors multiple points in the circuit, it's too bad it wasn't programmed to flash out a trouble code using the LEDs when it goes into shutdown mode. That way at least you'd know which input triggered the shutdown.
It actually does. If a fault condition is caused by over or under voltage or over current on a tube that led will flash. If it is something that is detected on both tubes then both flash. In this case there was drive missing to one mosfet and thus the voltage was low to both tubes. This is a fault that should never happen, according to the designer, whom I was in contact with via the distributor for north america.
Interesting that it's using PCL86, that valve I've only seen as the audio output in televisions. P series valves were intended for series connected heaters, commonly used in TVs, rather than parallel connected 6.3V heaters, like the ECL86.
PCL86 was designed for TV! This is probably why they designed thius amp like this. I am sure there was a huge inventory of PCL86 (14GW8) and ECL86 (6GW8) tubes kicking around. Of course the PCL japanese version used 14v heater, and the American version 6GW8 used 6V, and that is why the jumper inside, so if the 14v tubes go out they can be replaced with 6v versions.
Interesting how it is a hybrid amp, where it uses tubes but has a solid state power supply and safety circuit, and how the B+ supply is derivied from the lower voltage of the wall-wart.
It is not a hybrid amp.
The solid state components are not in the audio circuit. It could very easily be mains powered with a conventional transformer. The design was to use an inverter in the power supply as a safety precaution so everything can be monitored for any faults.
A hybrid amp would be a solid state power amp with tubes in the audio path, such as a luxman lv103 or 105
Would you be able to take the signal from the working signal output of the IC and connect it to the fet that doesn't get one? the timing wouldnt be right, but at least the fet that does get the signal wouldn't go into compensation mode.
Was my 1st thought too, just try the functioning Pin with Signal and "bridge" it to the FET that gets the "bad" Signal, I looked at the Schematic, and even a small Signal from the "other" Out is send to the Fet through some Resistors and Caps around them FETs....
Sure and the voltage from the output of the transformer would drop to 0. They switch back and forth out of phase to create a N-S-N-S polarity on the transformer. The output like thin ^v^v^v^v which is full wave rectified. With only 1 output working it is more like this ^ ^ ^. Half wave basically.
@@12voltvids So both Fets would work on the positive swing only and might create another overvoltage situation, since the both work on the same pulse. You need a signal delay that shifts one signal to the "off" time of the original signal. or a new IC *lol*
or is the non working FET responsible for the negative swing? oh yeah... dang.
@@Asriazh You did see the pulse width change when it fired up right. This is how it regulates the voltage. A sample from the DC is fed back and measured which changes the duty cycle of the fets to control the output voltage of the transformer.
won't be possible to extract the firmware out of that PIC n get a new one and programme it with that firmware n try ? isn't that possible ?
I'm kind of glad that all of the amps I've made don't include "smart" features. I wonder if the original assembler "cooked" the IC while installing it. I really prefer to socket IC's on PC boards.
You should try one of the modern designs with the auto biasing. They really sound great and don't require re-biasing through the life of the tube, plus you can roll tubes any time you choose and the new ones will sound perfect from first installation. This plus automatic bias through the life of the tube means no sound changes throughout the working life. I have both, and the modern self bias is superior. Incidentally this amp is not such. The TU8200 is though.
I have manual adjustments with current meters on my tube headphone amp. I would LOVE to have automatic calibration.
@@gavincurtis the auto bias on my tu8200 is flawless.
Question, my tube headphone amp is a Little Dot Mark VI. Balanced output.
I habe multiple sets of tubes. Very knowledgeable in electronics, but I dont know tubes..lol. What I do know os they are unbeatable sound.
I am having a problem where one channel drops out at low volumes. You habe to crank the volume rapidly to "awaken" the dead channel.
Bias currents are correct.
Anything known with tubes that could cause this? Not a mechanical issue. It can fo days without problem. Other times it wont work long enough to listen to one song.
Is this something you could diagnose as my time to learn tube topology is limited. My company ships electronic gear worldwide, so unless it falls out of the plane at 30,000 ft, it will get to you safely and you would reuse the custom packing blocks and box to get it back to me.
This new youtube I cant see what I am typing. So fristrating. So ignore the typos as I cannot see until I publish.
I have two sets of tubes. No difference. No microphones with my Tungsol tube set, but still drops out. Bias current is stable for all 4 output (balamced). I suspect one of the 4 channels is dropping out.
were do you get the voltage for the tube plate?
DC to DC converter. 2 mosfet driving step up transformer. Steps up to 220 volts.
Could you get a PICkit or similar and read off your known-good IC & clone it?
Don't see why not there is even a program header right there. Jtag it and clone
@@12voltvids Almost surely read protected.
The design of this bothers me a little bit. they are driving ordinary MOSFETs from a microcontroller directly with no gate driver. this is a seriously BAD idea in more ways than one. They could have went at least with logic-level FETs. it would be less taxing on the microcontroller, and it would be able to drive it into full saturation a bit better. So I wonder if the design flaw caused the PIC to fail. it may not have the drive current for those FETs, or just barely. Back when I experimented with a microcontroller based SMPS, I had to use a gate driver. I had issues otherwise.
This is a 2sk4017 which is a logic level mosfet. 4v will drive the fet into full saturation. it has a max gate voltage of 10v. Not the newest of designs but one that is stable and been around for a long time. No need for a gate driver with this, just a pull down resistor to turn it off when TTL drive voltage is removed. My unit has been running flawlessly for 3 years and it gets a fair bit of use.
I am not saying it doesn't work, I am just saying ive had bad experiences when designing/using circuits built like this. ive had troubles. I guess it all depends on switching frequency, currents, and parts selections I suppose. In this case, PICs are usually around 25mA Max drive current from any of the GPIO pins such as the PWM outputs used in this case. This is cutting it close.
thanks for video
Couldn't you of temporarily swapped the IC from yours since you have the same unit, just to verify the problem?
If there's a problem further down the chain that isn't clear, he could pop his IC.
Not about to put my amp at risk. These things are expensive. I think mine was about 400.00 by the time taxes were paid and the big brother to it was 1120.00
Thats serious money for a bag full of parts. I want to build the even bigger brother, but unfortunately there is a wait list of over a year to get that one. I have had my name on the list since it was announced and no email informing me that I can bring 2000+ for in and exchange it for a bag of parts and then another 600+ for a couple of vacuum bulbs.
@@12voltvids I agree......As a technician, I don't like to break anything that's working properly.
I'd have been horrified if he'd done that.
I would HIGHLY recommend removing your Metal watch before working with LIVE voltages!
Why, I like to live dangerously. I ride a motorcycle too.
@@12voltvids Well good for you. I've been an electronic bench tech for almost 40 years. Love your videos but is it really a good idea to teach this bad safety practice to others who are trying to learn?
Love your videos but this time I think you would have done better if you didn't use the diagram you would have figured it out better and faster using your Great electronic knowledge . Looks like your Diagram made it more difficult this time .
Dang that sux
I've been waiting for another vid. Glad to be the first to comment. Another great informative show. Thanks
Quite a novel little amp