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Tech Chat Cap & Board Swappers Nightmare; Component Level Debugging!

 
crustytv
(@crustytv)
Vrat Founder Admin

One of my go-to channels I mentioned in this lounge thread, is CuriousMarc. Nothing better than grabbing a coffee, sitting back and watching Marc and his team at work. If, as I mentioned in that lounge thread, you've not checked out the Apollo AGC restore, you really should.

The latest project, a recalcitrant Switch Mode PSU. Maybe after seeing this, those that found the 3K SMPSU intimidating, will find it less so.

Part 1:

Part 2:

If you're curious (pun intended) you'll have to tune in for part 3

Part 3:

Part 4:

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Topic starter Posted : 22/05/2020 9:08 am
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Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered

Well, there was always my repair on the Tektronix TSG271 PSU thread, and the tale of the Sony 'ghetto blaster' whose crackling on one channel turned out to be a faulty 'via' on the double-sided PCB...

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Posted : 22/05/2020 12:27 pm
turretslug
(@turretslug)
Honorable V-Ratter Registered

I found it significant that even the folk at the mighty Tek seemed to have overlooked the problem of miniature film resistors operating at high voltage going open circuit or at least residually very high resistance- I recall a steady stream of 17xx monitor 'scopes coming in with tiddly little SMPSU start-up resistors costing cents stopping thousands' worth of kit from powering up and doing its thing. That snubber failing is a nasty sting in the tail, too, another case of ha'p'orth of tar and all that.

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Posted : 22/05/2020 2:37 pm
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered

@turretslug

Ah, you as well !!

I think I put a VR37 resistor in that position in the TSG; my SPG-271 uses a different PSU altogether.

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Posted : 22/05/2020 2:39 pm
crustytv
(@crustytv)
Vrat Founder Admin

If you're interested, Part No.3 added above ^

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Topic starter Posted : 23/05/2020 9:20 am
freya liked
crustytv
(@crustytv)
Vrat Founder Admin

Part No.4 added ^

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Topic starter Posted : 24/05/2020 9:24 pm
Red_to_Black
(@red_to_black)
Noble V-Ratter Registered

Welcome to my world Chris, whilst I never had much, if anything to do with the Thorn 3k psu I did do battle with master/slave smpsus and many other types devised by lucifer himself ? 

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Posted : 25/05/2020 12:57 pm
crustytv liked
Cathovisor
(@cathovisor)
Illustrious V-Ratter Registered

I'm thinking a particular brand of professional OLED monitors here, which take the mains in, create a bulk 24V supply and then run a string of switching regulators from that. But they're easy to fix - you just look for the 7-pin DIL chip with a hole in it.

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Posted : 25/05/2020 2:19 pm
Red_to_Black
(@red_to_black)
Noble V-Ratter Registered

I was thinking more Thomson/Ferguson types along with some later Vestal LCD PSU's ☹ 

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Posted : 25/05/2020 3:08 pm