Astron RS-35M Shuts off Overvoltage? Working perfect over a month since this repair! 2N3771 2N3772

This is my Astron RS-35M 12 volt (13.8v) 35 amp power supply. It has started shutting down with a over voltage issue. I am not sure if it was the output transistors but I replaced them and it has been going strong for over a month now!
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00:00 Intro and a look around
04:32 Unsoldering base drive
05:29 Testing with drive disconnected
05:55 Removing the old output transistors
06:25 Testing old transistors
07:36 Testing new transistors
08:41 Installing new transistors
10:30 Testing new transistors
11:19 Reinstalling base drive and cleaning board
12:04 Testing after repair
13:08 Final thoughts / Closing words

[@stirlingschmidt6325]

Good stuff, good work! A couple tips - to turn off the pass transistors, the base needs to be grounded rather than floating. Once the bases are grounded, a small load of maybe 1/4 A (56 ohms) at the output will enable an accurate reading of output voltage. The combination of floating bases and the 11M impedance of the meter alone made for a small, unrealistic voltage measurement.

[@rayhill1855]

I really like how you cleaned the board.

[@montygore]

I did not know you was a fellow ham. Ive been a ham since 1984. Another great video. 73 W5DN

[@Sctronic209]

Enjoy your channel.

[@barryg41]

Happy new year to you Steve.

[@norcal715]

New Year, Barry. I am leaving off the H-word until the year proves to better than 2020 or 2021

[@kahlid-ataya]

this video is a new year's gift 🎁 thanks for it

[@norcal715]

Happy New Year!

[@K1ZEK]

Happy New year to you and your family...Leo

[@norcal715]

Happy new year!

[@TheKuldeepsingh88]

Happy new year to all of you

[@norcal715]

Happy New Year!

[@KoenOnbekend]

Happy new year! Great and informative video as always! I could be wrong but those new transistors look suspiciously like those fake Chinese ones with the large blue insulators, same print too. They seem to work at first but die quickly under load, the die is tiny in them.

[@marka1986]

Somethings up with the original transistors. Never seen a standard to3 audio or pass transistor with that much hfe. Maybe 20 to 75.

[@norcal715]

My thoughts exactly!

[@cajuncoinhunter]

That's a good sized tube of compound, How much was that 35 to 40 bux ??/

[@josealfredocuevas]

Great job on the repair👍🏼 I have a question on a power supply you might be able to help me with. it's a pyramid PS-52KX and the problem is it's supposed to do around 50 amps but it's only doing 15 amps and when you have a load on it I'm running a CB radio the problem is when I key the microphone and the radio draws amps I get a loud hum from the power supply when I unkey the hum goes away and it only draws 15 amps the voltage is fine..

[@stargazer7644]

A loud hum under load can be several things. See if it is mechanical - if the case or something inside is loose and vibrating. If nothing is vibrating, check the rectifiers.

[@AB1Vampire]

Question: At 11.30 when you clean the PCB with brush, what fluid are you using? Thanks for posting your 2N3772 test results. I'm doing the same with my Pyramid PSU also using 3772's but a Peak-Atlas.

[@norcal715]

I use regular Acetone available at any hardware store.

[@MMWA-DAVE]

So, the million dollar question is - Are you the Dave on the business card? 😎

[@norcal715]

No, That is Dave at Grants Pass TV Repair, Check you his channel kzbin.info

[@MMWA-DAVE]

@@norcal715 Damn, I thought we were getting a face reveal 😁

[@FulvioGa]

@@MMWA-DAVE you can watch him in a video on GrantsPassTVRepairs channel.

[@MMWA-DAVE]

@@FulvioGa Thanks

[@cajuncoinhunter]

@@MMWA-DAVE I have seen his face many times in his video's, him and and dave would pass for cousins though....

[@AliAli-dr3th]

Hello Mr.norcal715 .. Thanks so much .I'm beginner technition.. how I follow up voltage in circuit board ...& also some capacitors..47uf..50v .. or 1000uf 16v .. when I tested should be get same voltage or different value... Thanks .. Ali ...khartoum.

[@norcal715]

Its hard to tell, most capacitors in a power supply application will have approximately 60-80% of their rated value as far as voltage. But in different applications a 16v capacitor may only have a volt or two depending on what they are using it for. Try and find a schematic, it will be a great help.