Fix A Power Supply! Diagnosis Repair And Restoration.
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- čas přidán 15. 09. 2020
- Let's diagnose and repair a power supply together! Lots of information on the repair process and the steps needed to get power supplies working again. Click the SHOW MORE tab below for links.
To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: / mrcarlsonslab
#learnelectronics #restoration #repair - Věda a technologie
To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: www.patreon.com/MrCarlsonsLab
I absolutely must schedule myself a class time after work to learn from you before my capacitance to absorb wanted knowledge shorts out due to my age. Sure would nice to do something of value before I kick the bucket.
Is it possible to know a bit of your background work/studies etc... ??
@Santa Clause Try watching Electroboom :D
Who was the Mfg. and what was Model # of this Power Supply?
Paul, your skillset and motivation to deliver quality work (and content!) never ceases to amaze me. I absolutely love it. Proud to be a Patreon of you 🙂
Mr. Carlson, you know as much as I do at this point... Me : LMAO I wish !! that's why I watch every video you make, BEST TEACHER EVER!!!
Got a chuckle from that too.
Same here
Absolutely no way I could know as much as he. Probably ever.
This man has the best - voice set performance / vocal, mic audio in my opinion on entire CZcams; video voice is so clean and crisp w/ hint of old radio sound mic (without any his or interface) I just love it + love every now video he pushes out 😎 for me yet again 1h of quality - educational program; well spent 👍
Thanks for your kind comment Nenad!
Well said, sir!
I couldn't agree more. I watch because it is so impressive to see such skill. A totally absorbing experience every time.
I fall asleep every night listening to his videos. There’s nothing better to dream about than old capacitors and vacuum tubes.
@@michaelh2899 Slightly creepy but saved by it's eccentricity 😄
This is just pure art, from the root cause analysis, to the electrical design, to the physical layout of the circuit board, to the individual solder joints. Fantastic, these types of videos are what keeps me coming back!
Thanks for your kind comment and feedback Jim!
That Fluke tricked me haha. It looked like it had somehow been sawn in half and still working when you were probing the supply rails on those ICs. Remote display. Very cool feature after looking up that model. Nice repair, too. Wonderful content in some tough times lately. Thank you so much, Paul. It helps me and many others keep trucking.
Ha yeh he confused me before on another vid with his spooky headless meter
Others: The regulator IC is fried, gotta get a new supply.
MrCarlsonsLab: I'm going to design my own new board with the same footprint.
Totally admire you sir!
Still Others: I'm going to order a couple of the original ICs from eBay rather than redesign a power supply that has worked well for 50 years.
@@patlaw53 Exactly, 3 mins on ebay shows it's not exactly an unobtanium component nor what I would consider expensive compared to building an entirely new power supply
@@patlaw53 most of the ebay stuff is either obtained from e-waste or chinese fake parts. I will never trust ebay on expensive components. I would rather pay extra 2 or 3$ on digikey , mouser or lcsc. & A newer circuit with cheaper & more accurate components is way better than waiting 1month to receive fake chips or e-waste chips that will go bad after few months.
@@KuntalGhosh I buy dirt cheap electronic components from China all the time and they work perfectly fine and last a long time, even the non-original ICs. When you buy from those American stores, where do you think those components were manufactured? The only exception is electrolytic capacitors where I must be sure I get original Japanese brand ones. In this case for an old linear bench power supply that is not going to power critical or life saving equipment, I see no issue in using cheap non-original Chinese ICs to get it working. Chances are it was better manufactured than the original decades ago and may last longer.
@@metricmine nope. The fakes r most of the time some different ic that got rebranded.. so the ic never performs to the spec , most of the times they pull it out of old electronics and they die soon .. i have had problems with many AliExpress chips. I regularly order power supply control chips and catv booster chip as i have a buisness of catv and isp & i repair most of the stuff on my own to save a lot of money and power supplies regularly die due to lightning or other environmental damages and using cheap knockoff chips has caused me a lot of trouble and more down time than what i saved by going for the cheap route! ..
This is one of the best instructional videos I've ever seen on CZcams. You are very gifted Mr. Carlson. That is why I have been a Patreon subscriber for over a year now. I do wish that I was younger again & Went into electronics repair when I was going to signup to Devry Institute back in 1972. But I didn't have an instructor close by with knowledge like yours to Elmer me along. I chickened out at the last month of application. So I turned to a 50 year career in motorcycle mechanics instead. At 70 now, I've got the time to listen & learn from you, But I just can't turn back time. I just wonder where Electronics would have taken me in this wonder world of digital technology ? I started as a Novice Ham building Heathkits with tubes which I still have But don't turn on anymore because I can't get parts & Couldn't get them working again with my limited knowledge. THANK YOU for sharing your gifts of knowledge with us ! I do hope you read this.
Thanks for your kind comment Robert!
I can tell you one thing, I got no idea of what you are talking about, but I enjoy your videos.
When I was a kid, I always enjoyed watching Don Herbert on Mr. Wizard's Lab. You transport me back in time with your clear explanations and graphic demonstrations of how things work.
Can't believe I've never heard of that show before, looks fun! I'm getting some episodes from archive.org now
I do remember Mr. Wizard. You must be an old curmudgeon like myself!?
Im going to watch this to save myself from creative depression. Mr. Carlson is almost like a superhero, especially in soviet cartoons. Thanx for the video!
In Soviet Canada, Carlson Fix You, Eh!
@@ChatGPT1111 Soviet Canada? Am I get into a parallel world? :)
We were so poor when we were kids that we couldn't afford batteries for our "Operation" game. Then one day my cousin figured out a way to just plug it it into the wall outlet. It was sure an exciting game after that!
Thanks for the laugh Jim! :^)
@@MrCarlsonsLab "Try this AT YOUR OWN RISK - take care"
And now you are a family of wealthy surgeons all thanks to your cousin (who is either an electrician or in jail).
We were so poor that when momma let us eat from paper plates, we had to erase the dishes after supper.
Your nose and that of the patient lit up simultaneously!
Oh boy, does this bring back memories. I think this is the Anatek 25-2 lab power supply. I used to sell these to schools and labs across Canada. Anatek was started by Allan Crawford who also started Allan Crawford Associates. I was a sales manager at ACA. Anatek was more importantly a designer of custom OEM power supplies. Our largest order was for a custom designed switching regulator multioutput power supply for NCR cheque sorting machines that were produced at a new plant in Waterloo Ontario. Volume was so high that the power supplies were shipped daily in custom made shipping containers that fit directly into the cargo hold of 747 cargo jets. Anatek was the 2nd largest customer next to the Canadian Post Office, Vancouver to Toronto!
If anyone can relate to these facts, I will expand on the story of how this large order was won!
Brad Watson
Thanks for sharing that Brad!
Every time he says, "You know as much as I do," I laugh. No, no I do not, sir.
Paul, you're a very smart guy and thankfully you live within our time. I am constantly surprised at the things you do with circuitry design, and I can't thank you enough for the tips and pointers you've taught us over time. If I could continue to be a supporter on Patreon I would do it in a heartbeat, but Covid-19 has affected my health and wallet these days, I reluctantly had to back away from support. As soon as my financial situation is restored, you best believe I will return to Patreon and supporting you once again.
Thanks for that video! Even though I was tired as hell I still sat here and watched all of it becaue you've put so much effort into making those videos, and they are clearly very informative and enjoyable. Especially because your videos are models for what can be done to help the planet: Reuse equipment by repairing it, not buying something new. I wish there were more people like you.
I appreciate that!
MR CARLSON THAT IS A LOVELY PIECE, BEAUTFULL LAID OUT AND LOOKS GREAT QUALITY I JUST WANT TO SAY THAT YOUR CLASSES TO ME ARE PRICELESS AS IM 50 AND STILL LOVE TO LEARN AND ALWAYS DO THANK YOU FOR SHARING YOUR KNOLEGE TO US ALL YOU ARE AMAZING
You are very welcome Patrick!
Your videos are so therapeutic, and always remind me of Christmas, sitting in a dark, warm kitchen in the middle of the night on a chilly winters night, having just discovered one of the best engineers in existence.
Thank you ever so much, dear Paul, I come back again and again to your channel, a real Rolls Royce of engineering sources. I hope you have no more cracking trees and iced wires this winter :)
God bless you all. Shalom. Blessings.
Matthew.
Thanks for your kind comment Matthew!
I have these visions of Mr. Carlson's Lab and My Mechanics joining forces in the future..."This electronic part is bad and unobtanium"..."I make a new one." Love the channel Paul please keep them coming!
That would be a hell of a collaboration! My two favorite CZcamsrs by far
@@midjetville Yes, it's a real pleasure to watch experts at their craft. These two not only restore but improve whatever they're working on.
You're so calm while you're working on equipment. I evaluate repairs on a "curse scale" From a 1 curser to a 10 curser. 😁
Stumbling upon this channel years ago and subscribing has been better than four years of electronics basics classes in college
Is it just me, or is the TO-3 the most beautiful transistor package ever?
it inspired my avatar/business logo...
I used TO-3's as cufflinks once :)
@@dirk-janvandenbroek9947 that is actually not a bad idea. I think I might still have some new 2N3055, military spec somewhere...
I don't like the TO-3, they're difficult to mount and insulate, especially on PCBs. I like TO-247 or TO-264 much more, but I'm also a MOSFET and switching power supply guy. :)
@@stormeagle28 yup, but linear supplies have their niche, especially in ultra-low noise applications. TO3 mounting and insulation is a pain, but it's a very worn road, there's tons of documentation, I just find there's no need for through-hole components in power electronics these days and flying wires all over the place just create unwanted aerials also adding to the capacitance and inductance of circuitry
Nice design Mr. Carlson. I built my +/- 15v supply using 2 LM723s around 1980. Still going strong. Rock solid regulation, no noise. Love those chips!
That’s a beautiful example of a star ground, Paul! It occurs to me that many of your viewers might not understand the concept and why it’s essential in devices like these. Perhaps you could explain it in a future video?
I am a newbie and have taken up electronics as a hobby. I feel empowered by repairing old radios (replacing capacitors, fixing broken traces, hunting down shorts, etc). I was amazed at what you had come up with in order to keep your old power supply running. And I agree, that PS is a beauty! I love old analog equipment like that and would have been crushed if I owned it and found that replacement parts were no longer available. Your knowledge, expertise, and talent to design the replacement board on this unit has encouraged me to become a patreon member. This video has sealed the deal for me. There is literally nothing that you cannot fix! Great work!!
I'm really blown away by you designing a new control board for that old power supply. Laying out the double-sided circuit board really looked awesome. Giving old equipment new life is very satisfying.
Interesting technique there. I used to service Lambda power supplies for a CNC company in the late 70s. I forget the number of the regulator chip (could have been the LM723, I don't quite recall), but whatever it was, it was housed in a metal can. Nine times out of ten it was the pass transistor, one out of ten times it was the regulator chip. Got real good with a solder-sucker on those suckers. Never once tested them using the pot method employed here - that's a new one for me. Just goes to show you can teach an old dog new tricks!
Apparently your LM723s (?) weren't socketed, so the pot test would have been a bit harder to use :-)
@@theskett That's correct, but in a production environment, once the chip is removed it is simpler to just replace it with a known good one than to bother testing the supply without it. However, for one-off troubleshooting applications, Paul's technique could be useful.
@@sincerelyyours7538 True, dat. And don't get me wrong, I noticed that Paul's technique was pretty smart! :-)
As always you are so meticulous and thorough, it makes me wonder if you are human at all. Beautiful work!
Thank You for your kind comment Shahriar!
I really like your careful and methodical approach to any of your bench work with an emphasis on safety. Something that was instilled in me as an apprentice back in the 70's here in the UK. In this project you sensibly check the discharge state of the filter capacitors, but your unit had no positve or negative pre use test state and you declared the caps discharged as none of the lamps lit and then went out. You may have just used the unit earlier and knew it functioned okay, but the safety mantra we were taught was " regularly check your test gear, so you don't check out" If you get a null reading check the test gear against a known source, especially when checking for high voltage. Keep safe and carry on with these great videos.
I am an old engineer (retired) and now looking for a project to fill the time my wife doesn't fill (with her projects). I have been enjoying your restorations and learning whole lot extra to my experience in satellite communications (which involved very high voltages and RF radiation from HPA's and TWT's). I have long intended to restore a Bush VHF.54 radio that my late father-in law owned. It is about the same age as myself and I just hope it is not as stubborn and cantankerous.
Thanks for sharing your story!
When I clicked on this video I, by no means, expected more than a quick repair/restoration - I didn't expect a complete control circuit rebuild! Beautiful and elegant work as always Mr. Carlson. Thank you for sharing these insights with us; it's always much appreciated :)
Edit: the additional near hour (!) you spend explaining all of this in even greater detail (including all about the reference noise and how you did your board layout) on your Patreon is absolutely priceless! Thanks heaps for that especially. :)
Glad you enjoyed J!
I’m only 6 mins in and I know I’m giving it a thumbs up 👍
I always give a thumbs up before I start watching.
My brain thought that fluke display was edited in.
I thought it was a double exposure or video overlay 😁
That was my thought exactly, cool where the meter face separates from the body of the meter
@@randyelliott9495 A guy I work with has one. dropped it on the floor! $$$$
Same here. I'd never seen a removable display like that before. Cool stuff!
That looked like some amazing CGI. :)
The Bob Ross of Electronics! Best! Job
I wish you’re the one of my very helpful neighbor! I will trade mowing your lawn to teach me electronics
No joke If I owned any PCB from Mr. Carlson It would be framed and energized (:
Amazing. You are such an asset for the aspiring to understand electronics and the associated science and tech of what You do. Thanks Mr. Carlson.
Thank You for your kind comment Dan!
Thank you. Nice repair and power supply.
Absolutely right on sound quality. Same mike as The Blues Brothers used.
"The reason they socket those things is for a reason". Wise words, there. Should be a T-Shirt ;-/
I just pulled a 12 hour shift and I shoulda been in bed but I haven’t got to watch you in a while .
So I watched the video ,, you are truly enjoyable to watch , and very good at explaining “why” . You’re awesome , love your work . Now I gotta sleep !! 73’s to you from middle Tennessee 🇺🇸
KK4ISW
Welcome back!
When Mr. Carlson showed that new board I was amazed. It looks really nice. What a skill to be able to do that.
very cool design, and it was nice of you to pretend that you didn't know it was the IC's the whole time LOL.
For future video ideas, i for one would love to see videos on using gear to calibrate other gear, and the nuances involved in measuring RF as opposed to measuring AC.
thanks for all the great content!
I love your videos when you make a replacement board. It's an excellent way to give a new lease of life to an old faithful piece of equipment. I've seen you do the same before with other equipment. Certainly takes some genius in electronics! 👍🏻
Great to see someone who is an expert in analog circuit debugging and methodical in their approach in fixing things without taking short cuts. I just finished repairing a Pyramid PS-26KX supply which had destroyed itself when I test shorted its output. How dumb was that! I thought it would protect itself, but unfortunately the event must have been fast enough (or inadequately designed) that the SCR blew itself, one of the four 2N3772 transistors shorted base to collector and the UA723 regulator chip also blew itself up. The fuse of course was perfectly fine! I have replaced most of the damaged components some of which were obsolete like the SCR, but am waiting for a replacement 2N3772 transistor. Some of your techniques to isolate the problem and bypassing the regulator to test the pass transistor was very useful. In my case, I used another supply (with current limiting) to apply a voltage directly to the base of the pass transistors to control the drive voltage, open loop. Thanks for the tips.
Watching somebody solder a resistor to a VR just laying on the bench. The hands of a surgeon. Without tying it down, I would have chased it around my bench, through the kitchen and down Main Street.
Amen brother that little resistor would still be rollin, rollin, rollin.....
Whenever I see a panel meter that says "Amperes" I know I'm in for a good time.
First time watching a Mr Carlson's Lab video. WOW!! I'm blown away!! What a great teacher, excellent presentation, excellent soldering skills, excellent diagnostic skills. WAY, WAY beyond my ability. This has to be one of the best channels on YT. Instant subscriber, even if I do end watching the video feeling like I'm as smart as a length of 2" x 4" LOL!!😂
Does anyone know if there are thousands of specialists as knowledgeable as Mr. Carlson or is he one of the rare few with that level of expertise?
He's very knowledgeable and experienced, for sure, but this is still at (advanced) hobby-electronics level and on relatively simple equipment. So, yes there are many thousands of people in the world who could do this.
Your welding looked incredible . Just wow ;-)
Woah! Never saw that remote display before on your Fluke DMM. I thought you were doing an illusion! 😆
It freaked me out for a moment, I was convinced it was an editing trick until I spotted the 'Remote Display' text on the readout
That would be a fun trick for an instructor to play on his students, like the magician's trick of sawing the lady in half, this could be sawing the Fluke meter in half.
@@vancouverman4313 We have one of these at work (and a pile of 179s) - at first I thought it was really neat, but I came to despise it, because the AA batteries in the head get drained *very* quickly (in contrast, the 179s simply run off a 9V battery that lasts forever), even when it's not disconnected from the body :/
Glad to be back in the lab! Amazing videos.
Thanks!
The best audio on CZcams 😃
That was absolutely beautiful! You, sir, are the Bob Ross of electronics!
The question is, why did both ic's die a the same time? Essentially, there are two separate supplies in one box.
He plugged the thing into the wall the wrong way. ;)
@Dillon Kluksdahl looking at the IC I'd imagine it's the same problem that's killed a few discrete linear bench supplies, zapped Zeners... usually caused by a power spike from the mains, I'd install a surge arrester and a filter in line with it
Maybe they didn't die at the same time.... maybe one died and the previous owner used the other side until it died. Who knows. An interesting thing to me is that this supply doesn't have the range switching setup I've seen in other units with linear regulators. In order to keep the power dissipation under control at low output voltages, they would switch to a different tap on the power transformer. This lowered Vin and kept the power dissipation reasonable, plus it helps keep the output transistors away from secondary breakdown area on the SOA curve. I wonder what would happen if you set Vout to say 3.3 V, current limit to maximum, and then shorted the output.
My question too! I was looking to see if someone else asked the same question. :)
@@davidhunt240 I'm surprised he didn't do any failure analysis of the IC since he had the schematic of the IC.
I'll never understand why would anyone dislike this
That's a really nice work again. I also like building and troubleshooting electronic devices as a hobby.
During my apprenticeship as an electronics technician for energy and building technology, we once built a controllable power supply in the vocational and technology center. It has a very simple structure with 3 transistors, a Zener diode, a few resistors, capacitors and a potentiometer. Although the circuit is very simple, it is very stable. Originally it was designed for a maximum of 1A at 6 to 12V output voltage. A few years ago I finally exchanged the series transistor for an "MJ802" including matching heat, installed a 12V 4A transformer and replaced the smoothing capacitor for a bigger one. I already had the transistor lying around. The power supply has worked flawlessly for years. Once the smoothing capacitor broke. I noticed this through an extremely fluctuating output voltage and the luckily short-circuit-proof transformer became very hot. After replacing the capacitor everything works fine again.
My tech project in college was building a 5V regulated power supply using the 723 regulator. Back in the 80s most all of the equipment I worked on had linear supplies that used the 723. When I worked 2nd shift I used to mess with the day shift guys by fixing the problem they were having with a supply they had on the repair bench but not telling them. I love those Fluke meters with the removable face. We have a rolling mill at work and now and then the Can bus gets to acting up because of a bad connection. I can hook the Fluke to the Can bus, go around to the different devices with the meter face and watch the meter as I tap on each device to find the problem. Very Handy.
OMG, first time Mr. Carlson re-uses a capacitor! Tnx for you video!
There are exceptions :^)
Those low-voltage soupcans rarely go bad, it seems like. The two/three-section caps in tube radios, however...
When you learn more in an hour then a whole week at school.
One of the best hours I've watched , well presented video. Billy from Scotland 😀😀😀
Thanks Billy!
Excellent repair and board build Mr. Carlson. Current limiting cutter-backer circuit works great.
I love watching your videos and am always impressed with your understanding of electronics. Thank you for making them.
Thanks for watching!
Your circuit boards are so fantastic to look at!
Ah, the good old 2N3055 - the EL34 of the silicon world, haha! A jellybean power transistor, p retty cheap and powertful, and damn ubiquitous. I've built a few power supplies, motor controllers and audio amps with these when I was learning electronics.
It's a splendid idea to redesign and make a new PSU board, and the 723 is a real deal classic. It's been around for almost half a decade!
As always, Mr. Carlson has produced nothing short of excellence.
Great video! And good to see that it also happens to other people that one project gets interrupted by another unexpected project. Happens to me, too!
The MC1466L is still available on eBay for about 5 US-$ while the LM 723 is also already on its way out as you said yourself. I think I would have simply replaced the two MC1466 with new ones from eBay.
Yup. 10mins effort, $12 for the two chips, job done.
Wonderful video. I can understand your desire to replace the multi-turn pots but now an accidental bump of the control might send the voltage outside the safe range of the connected circuit. Whereas, with a multi-turn pot an accidental bump of the control might only change the voltage setting a little bit. Please don't take my comment as a criticism, it is just my thought as to why the original designers would have used the more expensive multi-turn pot.
Why a potentiometer that can switch between them (push in or pull out maybe) or a psu with both and a switch to select between them
They also used the multi-turn to "hide" the non-linearity of the voltage that is inherent in this type of design. The voltage is commonly defined by something like V=1/R, and that inverse creates a logarithmic response to the rotation.
Look at 54:20, see how far he rotates the knob to get from 0V to 5V, then about 1/2 as much rotation to get from 5V to 10V, then a further rotation of the same angle takes it right off the dial (over 25V).
There's a few ways to deal with it, varying in complexity and effectiveness.
Multi turn vr definitely results in an even more stable output.
@@johncoops6897 I also had noticed the oddity of the high number of degrees of rotation at low voltage settings for a given voltage change and the low number of degrees at higher voltage settings for a given voltage change. I was wondering if Paul had used a log taper pot rather than a linear taper pot for the 10 turn replacement. If you really wanted a single turn pot that was relatively linear in terms of rotation degrees VS voltage change I wonder if you could find a reverse log taper pot to do the job. Back when this supply was built I bet such a component could be sourced, especially if you were building thousands of such supplies.
@@Vincent_Sullivan - I have been battling with a similar issue on the pots for DIY frequency/function generators. I have yet to find a good (low cost) source for Reverse Log pots (they are commonly termed "ANTI-log"), but some come up on eBay search.
I did find quite a few webpages relating to the creation of Log pots from linear pots by the addition of series and parallel fixed resistors that alter the linearity of the original pot.
Whilst not perfect, my (very limited) initial tests show that there is certainly an improvement, especially in the middle part of the pot rotation. Some of the circuits had strange results at the extremes of rotation, but overall it's a good start.
My next tests will be using a digital pot IC, as it seems that some of them can be programmed to log and anti-log characteristics.
Very nicely laid out 👍
What I like about this video is that you didn't use a dremel to open the power supply, neither did you short circuit it with a paper clip. Also, you fixed the power supply and didn't destroy it.
Highest quality video and audio, a pleasure to watch! Thank you.
What do you think could have caused both ICs fail at the same time? Power surge?
A chap upthread (sorry, their nick escapes me) suggests that turning the power off (presumably when the transformer cores are fully magnetized) would / might cause similar to a flyback spike; and because the transformers are wired in parallel, both chips would get hit by the same spike.
I'da expected the bridge rectifiers and large caps to have mopped most of that up -- but his still strikes me as a plausible explanation.
Not sure how one would prevent a re-occurrence; MOVs or GDTs on the hot side, or TVS diodes on the low-voltage side, maybe?
Seems like a only-once-in-40-years problem, though, so maybe not worth too much engineering :-)
I've been wondering about that myself...
Have the single version of this power supply at work and it failed the exact same way. Thankfully I found a handful of replacement MC1466 in a parts drawer so pretty quick fix.
huh. Hope MrC gives the failure reason in the vid
Mr. Carlson - Every video is a successful repair. I'd like to hear about or see a time you were stumped.
When I encounter that issue I will post a video. Thanks for your input!
That power supply looks amazing... i just love the analog meters , real gold nugget.
Since this supply went from working perfectly to suddenly not working on either channel, AND the culprit appeared to be failure of BOTH regulator IC's, but without the pass transistors failing as a cause for those ICs to fail......it seems pretty odd. I was hoping for some analysis into what might have gone on to cause simultaneous failure of two independent ICs that had been just fine earlier. This video appears to skirt around that issue entirely.
I also wondered why there were not even any initial tests shown upstream of the regulator....no tests shown to check the voltage at the filter capacitors, anything like that; It was straight to suspecting the pass transistors, and then the regulator ICs. This may have been a good guess, or an educated guess, but.....it all seemed quite a lot like Mr. Carlson already knew what the problem was, and really wanted to do a video on redesigning the power supply......?
agreed, I think this was staged to some degree
Mr carlson's extream knowledge and experience already told him where the problem was, he just needed to do some test to prove his theorem was correct.
Let's face it, he knows a whole heap more than you or I could ever know
Mr Carlson has been fixing power supplies for a long time and I suspect he made his living for awhile doing so. A linear power supply like that one is laughably simple compared to the switching supplies he was fixing or rebuilding routinely. It’s a pretty good bet that he thought the IC was a prime suspect before he opened the case. This is a guy who understands electronics at a very intuitive level. It is his superpower. Thank God he uses it for good and not evil ;-)
@@jgeorge6081 I agree mr Carlson has great electronic knowledge. But he 's still human, you know..:-)
I feel I also missed something here too, not quite understanding the linkage between both boards,excellently produced video, but left with more questions ,oh well that's why maybe i don't make videos LOL
I like the 10x pot :) To each his own, they say. I have the 50 Volt 1 Amp version of this PSU and love it. It has a few flaws (right side current limit control is flaky, left side voltage control is scratchy at low end) but looks like the ICs are holding out.
This one could use the concentric fine/coarse type of adjustment with gearing between the two so that the 10-turn could be driven faster with the coarse knob.
The troubleshooting, design and construction is excellence at its best!
He is talented.
MrCarlson “I’m just going to redesign this board”
99% of viewers “Just?” 😮
Another great video. 👍
This and w2aew are the best two electronics channels on CZcams, despite the fact every time I watch either, I realise how little I really know! 😂
Thanks 👍
So , I'm not alone in thinking that !!
The moon is too close , so I'll "just" move it ............
The Gandalf of eletronics
"You shall not pass...unless you hook up your isolation transformer and current limited variac first!"
I'm not even knowledgeable enough to call myself an amateur, but you explain everything so well that I still manage to learn a lot and enjoy it too. Thanks again.
Wow, really cool redesign of the board. Great use of the space.
GREAT JOB! Nice redesign! I really enjoyed watching this. What I am curious about though is what would cause both identical chips to fail at the same time? Granted they are old chips but it seems very strange that both chips would fail on what amounts to two independent supplies???!!?? Unless you had a surge on your power lines perhaps?
I can just imagine someone else in another 30 years taking that thing apart with an original schematic and being very confused.
..but pleasantly surprised. It's a Carlson! ;)
Always leave a circuit diagram inside!
Funny I was just working on one of these I built in school, in 2001, in Electronics devices & circuits 16 week semester one of nine to get my electronic certificate.
*Not as fancy or dual like yours,but a useful bench supply.correction its a bad c3230,and it tested good, on the diode setting ,lighted up when I clicked the switch. But on board, a little black near it, the To-220 package c3230 npn had megohm readings on ohm setting between base & collector instead of 460 meg ohm's aprox, on the new one. I ordered two new c3230. Its adjustable, 0-15 vdc. [ Now I can watch you work & repair.]
Most people: Faulty part no longer available. "Ah well!" Go out buy new power supply.
Mr Carlson: Nah!
CuriousMarc: Designing a replacement IC
@@fklabs6813 to be fair, the schematic of the IC is in the datasheet :)
Mr Carlson you can get those IC's off ebay for less than $10.dollars
Less than US$7 even, or five for $25. All from China though, so you have to wonder if they are old new stock, recycled components, or outright counterfeit. I don't think they'd be common enough to be worth counterfeiting and they look pretty good so probably not recycled, but what is all that old new stock doing in China? I'm not complaining though, the new board was a creative solution and I bet it works even better than the original.
That’s not the point. What educational value is there in changing an ic? Mr. Carlson’s aim is teaching us electronics!
This is amazing. I did not see a complete redesign coming. Beautiful work.
Thanks Joseph!
Yay 1 hour of Mc. Carlson's lab!! 😊👍
I dabble with electronics and can identify the pieces. But when Mr Carlson turned the new board over and explained it, I felt like a hog staring at a wrist watch. Stayed lost for a good five minutes.
48:46 That zener diode is the most beautifully shaped and positioned component I have ever seen
Thanks David!
Excellent design upgrade. I like how you even improved on the original.
So nice to see another repair video from Mr. Carlson. Just love the presentation and all the pertinent information for us all to learn from. Peace and stay virus free also fella. VF
Thanks for another masterful job-as usual. But I have no idea why the two ICs failed simultaneously.
This is what I'm wondering. What are the odds of both of them failing close enough in time that it seemed like a single failure? The boards look entirely separate until you get back to the plug side of the transformers. Only other thing I can think is a large shock on the case that somehow made it through to the ground of the ICs instead of getting all the way grounded out by the plug in time. That seems like a pretty far fetched guess to me, but who knows.
Of all the Mr Carlson's Lab videos I've watched, this one seemed unusual in its absence of thorough schematic examination and theory explanation. He didn't actually troubleshoot the problem, step by step, as he usually does, but simply jumped to the conclusion that the ICs were bad. From what little I could surmise, and admittedly I'm a long way from my electronics training and experience, so my opinion is hardly expert, the unit appeared to me to have two virtually identical channels, beginning with their power transformers, with nothing more in common than the line fuse (which presumably was not blown). Your guess is better than anything I could come up with.
logically speaking the only commonality was the line cord that fed both transformers, and maybe a ground plane that was also connected to the negative output post. so either a surge on the line or a back feed n the ground circuit. i wonder if his viarac is ground isolating and if he uses that to power his test equipment
Interesting that both IC's would die at the same time in what is two separate supplies in one case. What could cause this?
Could be a limiting resistor on one, but both at the same time is kind of odd.
Given no known direct cause, I'm thinking something external but common to both. EMP? RF burst? Cosmic ray burst? Neighbor experimenting with breeder reactor in shed sees bright blue flash? Let's hope not the latter...
Transient power spike.
This is a really beautiful work! New and serviceable new circuit with a bit of the old one :)
You impressed me again. I was wondering how you were going to fix this one. Just create a new board, WOW!
Hi i wiunder if you have any explanation for the failure of two ICs at the same time?
I was wondering that myself. Misbehaving old caps?
Most Likely a voltage spike on the line.
Vancouverman your probably correct but it is transformer coupled so much less likely than a modern switch mode
Full Wave Recked Hello!
@@allthegearnoidea6752 I was thinking maybe a lightening strike or a high voltage line coming down down on a lower voltage one.
Nowadays a MC1466L costs only $ 278.30 ! Good reason to redesign the circuit. As usually good job.
Used one just like that in the lab.....and those 14 pin IC's were usually going bad......great video.
"I turned the switch on and nothing happened."
In the world of electronics, a thing will work until it doesn't. Sometimes suddenly. LoL
I have never in my life turned on a power supply and had to supply zero volts. :P