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thanks Andy! And good point 😁

thanks! yea I still have a lot to learn about RF transmission and matching impedence. Appreciate your input and thank you for watching the vid!

I should mention that the TDS754 has 50ohm input which I had set. I was thinking this roll off was due moreso to the lack of bandwidth when measuring 250MHz on a 500MHz scope. Would I still need to terminate with 50ohm termination?

@@fmashockie Yes Frank it should be OK with a 50 ohm termination. Some scopes have this. You could check your generator attenuator against the hp attenuator you have.

Glad you found it helpful! Link for downloading MemTool is in the description

Yep thats correct!

If you're referring to the arrow on it, that could be. But by the end of the video, the circuit for the current loop was corrected.

Do you offer service on these? Can I ship you only the board for replacing the shuts? I'm in San Diego so shipping the whole centrifuge is not ideal. Thanks.

@@anytimelabtrader Yes! I just started taking on independent work. For lab equipment PCBs and power supplies. I can offer competitive pricing, quick turnaround times, and a warranty on repair. If it is equipment I already have here (like the XTR for example) no need to ship the entire unit. Other equipment that I don't have available, but you'd like a board sent would have to be evaluated on case by case basis as to whether the board or the entire unit is required to be shipped. Feel free to reach out via my email at fmashockie@gmail.com. But if you do wish to try to replace the shunts yourself, here's the link to the ones I use www.digikey.com/en/products/detail/sumida-america-inc/CPFC74NP-PS02H2A20/1879019

Thanks Andy!

Thanks Duncan! Really appreciate your input and feedback!

Yea that power supply was for a bigger beast! Ultracentrifuge that goes up to 90k rpm! This guy only does I think a max of 15000rpm (depending on rotor type). And yes the blue things are current transducers using hall effect technology! LTSR15-NP. I know one is involved in the protection circuit.

thanks for the feedback Joel! 🙏🙏

Thank you!!!

Hey glad to help you out but which part are you referring to exactly?

Hi Frankie,it,s the attenuation/ref level/variable and the bandwidth /resolution they seem to have concentric shafts all very complex. Also yours has a mechanical freq readout mine have electronic display (dont think its a counter just a DVM display). Thanks

@@mechmania8450 gotcha. Is yours a 8557A? I know some of the 8557s had digital readouts. So you need knobs for the Optimum Level, Coarse Reference Level, and Fine Reference Level. As well as knobs for the Frequency Span/Div + Bandwidth Res? Thats 5 separate knobs. Am I understanding you correctly? If not why don't you shoot me an email (will need a way to send you photos anyway). My email is in the bio of my channel

You might get some additional help by looking at the service manual. It has an exploded diagram of the front-end. Because yes both those switches are concentric. But one is tri-stacked (amplitude) and the other double-stacked. You correct it is a pretty complex set of switches.

@@fmashockie Hi Frankie Cannot find you email. I have a scale for the attenuation/ref level and I am making a knob in aluminum. However I am not share how the bandwith/sweep width works there is a hole on the panel. Had me confused for a bit with the atten knob which has a channel front to back however this is not needed but it must weaken the knob. But I still wonder how the bw/sweep works. I have repaired helipots in the past ,bad connection at end of wire wound track.. Use some agressive soldering flux.

yes! been meaning to get one of those for a while!!!

@@fmashockie :)

For switching power supplies, rule 2 might be check your frequencies (only makes sense if you have a known good unit). Aside from microscope inspection that someone else mentions, a thermal camera would often be helpful.

I'd say it depends on how it's rated. If the manufacturer simply says 8 A max, I'd expect it to actually live up to that for its rated lifetime, as long as it stays in the temperature range (and whatever other parameters). If they derate it under certain conditions, it should still be able to do 8 A for lifetime, provided you avoid the derating conditions.

@@markp5726 thank you! I was just curious because I've worked on a lot of lab equipment power supplies, and I've yet to see one that was not overrated a little bit. So I thought this was odd.

Thank you Joel!! Always appreciate your feedback!

Took me a while to make that connection but glad you still enjoyed the video! This is my favorite part of my job but I don't get to do it as much as I'd like. We'd be in bad shape if I was working on PCBs like this everyday!

@@fmashockie I use a cheap usb microscope with 800 times magnification to examine boards, and take screenshots of what I find. Not a week goes by that I do not use the microscope to look for stuff or take images to put into reports. Or look at the numbers on components.

@@Uncle-Duncan-Shack I might need to make an investment in a microscope that powerful. I think mine is only 10x

Thanks Charles! It's crazy right!? A SMPS that costs $7500 shouldn't be having this many failures so early in its lifespan!

Around a decade ago, I watched someone open up an audio amp. I don't recall whether they planned to fix it or wanted parts out of it, but we were all amazed when they saw that surface mount resistors had fallen off or tombstoned. I think they surrounded a microcontroller or something else that shouldn't get hot, so it was quite strange. The board also wasn't discolored IIRC. If the unit was produced when RoHS was new, I wonder if the wrong solder was used, with a melting point that was too low.

Thanks as always Andy! I really do appreciate your feedback both good and bad. I'll be honest - I wasn't sure if I was pronoucing hysteresis right 😂 I can definitely do a better job with the scope for you guys - make sure I give you a clear shot moving forward and ensure it is triggered properly. And I know the sounds from the inductor didn't sound too bad on video, but man this thing was chirping away in-person - especially at 250W! Thanks as always for taking the time to watch and comment! 🙏🙏

@@fmashockie :) probably my age (nearly 60) as to why I can't hear it LOL !! yeah a few little tips there...always interesting to watch !

that is one of the main reasons I do this!

Thanks for watching Stan and I appreciate your feedback!

Good point! I suppose I should have clarified depending on the symptom. But if I have no voltage on the secondary side as in this case, I like to check the controller first because the datasheets for them provide so much information and you can get a lot diagnostics from checking with a scope. And I'm not saying because I think the controller is the issue, but knowing it's operation mode (under voltage lockout, over voltage lockout, hysteresis, etc.) can lead you to finding faults with associated components

@@fmashockie Just remember, time is money. Otherwise I agree.

@@joelkist6493 ain't that the truth! You're right I probably could have figured this out faster going with your approach. But there have been so many videos done on repairing this power supply that I thought it would be cool to show how it actually worked.

@@fmashockie If the main switching fets are blown then its likely you also have a shorted output pin on the controller IC that drives the gate of said fet. For combination chips that control both pfc & smps you can still have the pfc portion working despite the smps portion blown, which you did.

@@spikester thanks for that input! Interestingly, the DAP053T was still sending gate signals to both HS and LS MOSFETs despite them blowing. I show that in the vid @30:46. I'm not 100% sure what went wrong with the DAP053T, but it seems to be a common failure in this supply from what I've seen

Thought you would enjoy this one Globe Collector! I was fascinated by this one when I opened it up as I don't have much experience with equipment like this. I can definitely spend some time outlining the circuit. Interestingly, the Signal Path just released an in depth video on HV Amplification. I'm going to give that a watch. I was very curious as to what that long shielded cylinder was. I did open it up and it had some passive components inside, but there was one super long axial component that runs almost the length of the tube inside. I couldn't tell what it was. I thought perhaps it was some kind of current monitoring device. The manual for this thing was a bit of a letdown - no schematics. So I can definitely spend some time mapping it out!

So I watched the Signal Path's video on HV amplification design I was telling you about. It is a perfect supplement to this video. He goes into much greater detail than I ever could on how these work and even does a teardown on another Trek unit - 20kV one! He defines the long cylinder. And you're pretty much right - it is resistive divider that allows for feedback from the HV to the low voltage circuitry. Also defines some other components I missed, like the light pipe optocouplers below the HV tubes that are used to send the output signal from the amplifier to the HV side. So cool! Definitely check it out!

The Globe Collector Returns! I hope you are doing well and that everything is good on your side of the globe! I was starting to miss your detailed analysis of my videos. I always learn so much from them. Thanks for that info regarding Q19 on the Vertical Driver board! Per the service manual, Q19 1855-0417 is on when Linear or 10dB/div is selected, and off when dB/div is selected. I was able to find the electrical characteristics on CuriousMarc’s website! Link here (drive.google.com/drive/folders/1e4pSjjSeVk8JM6O1EnnuL9jYS6FAK8hN). And you’re right: the on resistance for 1855-0417 is low at only 10ohms. It seems like 2N4391 would be a good alternative. Right now I have a J113 in it’s place and the unit still seems to work, but its Ron is 100ohms. I think I might do a J111 instead (I believe I have some of those). I also appreciate your offer for sending over some JFETs! Finding the correct material for those contacts was the most difficult part of this repair! And thank you for providing the correct material characteristic terms. Elastic limit is definitely better than ‘springy’ lol. Still curious to know what the originals are made of though because they seem a lot more durable than the CuBe fingerstock I used. Any thoughts on that? When I was looking at SAs to buy, I saw a 7L5 plug-in for sale in non-working condition. I almost bought it, but I would have had to grab a 7000 series mainframe as well. Maybe someday! Thanks for watching the spectrophotometer and autoclave vids as well! It felt good to solve that spectrophotometer issue. I enjoy sticking it to these manufacturers lol. And I’ll be sure to get those boilers properly flushed!

Oh, yes…the 7L5…I slmost forgot. I have two of them, one a froend bought to the door one evening snd I got right into it. It is s fiendishly complex circuit. Each individual circuit block is dort of easy enough to grasp, butbthevway thay all “talk to each other” is sheer digito-analog wizardry! I ended up buyong a second non-functional unit off fleabay just so I could swap functionsl blocks aroind between the two. I think the problem is in one or both of two sample and hold circuits that hold the centre freqiency horizontal position voltage. They use fancy Analog Devices opnamps with a swanky, low leakage capacitor in the feedback loop…this is supposed to hold about 99% of its charge for at least ten seconds according to the manual. In the unit my friend bought around…after fixing smashed multi position switches, bent pot shafts, shorted Tantalum caps, open circuit rail dropper resistors..I found that the outpus of both S and H’s were slammed to the negative rail. The charge is added to or removed from the capacitors via two ultra low leakage diodes inna TO-72 can on the input of the S and H circuits…these diodes sre still svailable and thay sre the ONLY diodes with this low leakage as far as I can tell…a dizzyingly tiny 1pA! About three orders of magnitude less than most other diodes! Currently I am procrastinating getting back onto them, the second fleabay unit is just sitting in there on top of the other one basically untouched. Still a bit pooped after the container move snd its the bloody middle of winter here in Tas, day temps around 50 pf your antiquated Farenheight and night temps around 40…. It is cycling between grey, drizzly and sopping wet to sunny and windy every frw days. Sunrise is 8.45 in the morning snd sunset is 4.30 in the afternoon. The day is gone before it starts! Glad the winter solstice has passed and the sun is slowly starting its southward move again. Mut be noce there in Philly though at the summer solstice. Go for a walk to the Stocks Bakery and get some of that cake and eat it on video…lot easier than fixing electronic gear! I went an bought some “Madeira Cake” at Coles…it weighed 450g, and since an imperial pound is 454g, I see why it is called “pound cake” and I suspect this is the nearest equivalent I can get here. Gave one to my father all covered in whipped cream as an 88th birthday cake, he ate about 65% of it in 15 minutes! Get back to you when I take the 7L5 “bull by the horns” again!

@@thanhhuynh272 I'll get to that bakery for you eventually! I think that will make for an interesting video... "what's he doing eating cake? I thought this was about repairing electronics" 😂😂

Thanks Joel! This one really tested my patience but I think the worst is behind me 😂😂 Always appreciate your feedback!

Thanks Andy! I'm glad I wasn't the only one who thought this one was pretty cool inside. I'm starting to run out of space! This one I didn't even know I had 😂

@@fmashockie :)

pretty neat right?! I love the HV shunt regulator tubes

Thanks Glen! Yep I'm starting to run out of space!

If you mean videos? They are in the works! I finally got the parts I need to finish the HP 8557A SA so hopefully that will be the next one. And then everything else on that cart is waiting for that to be finished so those videos will be next!

Thanks for that tip!! I wasn't aware of that product

Thanks Joel! I know it's not the most entertaining info but I like to try to help others repair this equipment without the manufacturer

@@fmashockie it is possible to have an SD image of Countess II. I do have an Countess II but does not boot at all, seems that SD is the problem. Can you help me ?

@@WirelessLanGrThessThesswireles shoot me an email. My email is in the description.

😂😂 there are a few things I handle off camera. Including the cursing in frustration 😂 thanks as always for watching Andy!

@@fmashockie :)

Thanks Andy! I know these types of vids probably aren't the most entertaining but I'm confident someone, somewhere will find this helpful. This kind of issue would usually condemn one of these instruments because most people aren't paying the ridiculous cost to repair it from the manufacturer!

@@fmashockie Could not agree more :)

Right!?? Glad I wasn't the only one who thought so! 😁

Thanks Nick! Yea I wasn't expecting to see the bridge rectifier failed like that! So cool!

thank you!! I appreciate it!

thank you! what field do you work in?

Yea so this is actually part 3 of a series of videos I did on repairing this unit's main power supply. If you go to part 1 (linked below) and scroll to ~4:30 mark, you'll see one of the I/O boards. Behind that board is the embedded CPU for the centrifuge. That is where CMOS battery is. It would be very easy to replace yourself. You just need to take the front panel off, remove the screws that the I/O PCB is mounted with and you can flip it around to access the CPU and replace the CMOS. FYI this is for an Optima XE series ultracentrifuge. It might be a different layout for a different model/series ultracentrifuge. That doesn't surprise me that they are charging you $3k for such a simple repair. ruclips.net/video/aNrVG8v53qw/видео.html

I'm so sorry to hear that Andy. I've seen these large lab equipment companies like Thermo do that. They will literally buy small companies just to get the rights to a piece of equipment they've manufactured and then they will slap their name on it. It sucks because I bet the original companies probably provided much better support. Well if it is any consolation, I hope this video eats into their equipment servicing revenue 😂😂

@@fmashockie LOL! I appreciate your efforts :) !!

thank you Joel!

thank you!

Is there a way to test the LWCO? I’m doing checks on a sterilizer and I’ve only been able to test the reliefs

@@shanepeterson8078 I'm sure there are a number of ways to test the LWCO and they come in a variety of different kinds. But what you can do is, first do this test when the boiler pressure is low, but the water level is at normal level. You can even disconnect the HV from the heating elements. But what you are looking for is 120V on the contactor coil. That should be there when the water level is normal, and the normal operating pressure switch is closed (and it should be if your unit is in the state I mentioned earlier). Now, you can disconnect the low level probe from the LWCO. If it is working properly, it should cut power to the contactor. That is the whole point of the LWCO - to prevent the heating elements from being energized when the water level gets too low. And that is the only reason for the low level probe. I might have mispoke in this video at some point, but the boiler can operate with only one of these probes. The low level one is strictly for LWCO. Hope this helps!