Repairing Switching PSUs for dummies ...
supervinx
Anyone has such a guide: Repairing Switching PSUs for dummies ?
I've quite a lot of dead PSUs, and no technician wants to help me ...
I've just repaired an old M24 PSU, but it was easy: no ICs, primary and
secondary on two separate boards.
Today I repaired a Sinclair ZX80 of a friend of mine ... he gave me the
pdf with the schematics and it was easy ...
But newer (?) PSUs are more complex and I need some hints, since I
decided the do-it-yourself method.
Switching PSUs are my black beasts ... never studied them ...
philo
here's a typical schematic
http://www.pavouk.org/hw/en_atxps.html
due to their low cost on the surplus market
I never though it was worth my time to repair one
other than replacing a bad fan
supervinx
But with different factor form PSUs, like the PS/s ones or the XT/AT, you
have three choices
1) repair
2) finding a replacement
3) try to adapt another board into the metal case.
Often repair is time consuming but cheap ... this afternoon the cause was
the usual shorted capacitor, but was a little bit tricky to find it ...
When the oscillator board dies and it uses a custom IC ... well ... it's
a pain ...
K. Martinen
> Anyone has such a guide: Repairing Switching PSUs for dummies ?
I am an Electrician, but for me, your problem is the same as mine.
So, my guide "for dummies" is: Buy a new one. :-/ Sorry. Can't help. I have the
same problem.
Bye/
/Kay
philo
In my situation I have several boxes full of spare supplies...
The last machine I repaired that had a bad power supply was at the place
where I do volunteer work.
It was a miniature PC with a tiny 90 watt supply.
It runs the security system and contains proprietary hardware and
software. They assumed the machine was not repairable and the security
company quoted them 4000 USD to replace it.
Though I suppose I could have come up with a similar supply
or possibly even fixed it...
I just used one of my spare 200 watt supplies and let it hang out the
back. I figured with a 200watt supply they'd be less likely to have
future problems
Considering I saved them a lot of money...they did not complain about
the aesthetics.
Plus, since it's for the security system
the computer is located in a place where no one would ever see it other
than the security officer!
supervinx
are proprietary, you need a lot of reworking also ...
The last I did was for an 8580.
I removed the big red connector from the dead CPU and attached to it a
standard AT male row of connectors (taken from a dead motherboard), so a
standard AT connector could be connected ...
But, in some collecting case, you won't have a PSU hangin' around ... so
for very old machine I try to repair them.
Generally I work guessin' and trying ... observing burnts and brown
signs, checking electrolitics ... in 90% of the cases I find the damage.
But some PSUs are very tricky, you must desolder a lot and ends up in
having a custom IC burnt and you stop there.
And you must pay attention, beacuse the rectified voltage is high, and
capacitors may store energy for days :-(
I have, in my repair list, an Olivetti 386 (long and slim), 5160 and 5155
PSUs, all of them with a secondary circuit fault.
Sooner of later I'll find the problem ...
philo
yes...
if you are working on vintage equipment I can see that you'd want to
keep it as original as possible...and it is worth fixing machines like that.
Though I have kept up with the times and have no problem repairing
computers...I am an old timer who started out in the vacuum tube days
and have restored many a vintage radio.
I did have a very difficult case once...and it was on my workbench a
full year. I worked on it whenever I got the time...and eventually I got
it working again.
One thing I've learned is that when things get tough...
walk away from it and come back to it later.
I've found many solutions by simply going to bed...
then waking up with my head filled with new ideas
Michael Kraemer
> Of course in the case of an ATX or standard AT ...
> But with different factor form PSUs, like the PS/s ones or the XT/AT,
> you
> have three choices
> 1) repair
> 2) finding a replacement
> 3) try to adapt another board into the metal case.
I have quite a bunch of ancient workstations
with defunct PSUs, absolutely non-standard.
No replacements, no docs. :-(
supervinx
5160 PSU with a short on +12 output.
Removed and checked all electrolitics ... OK
Checked all transistors ... found one shorted ... removed ...
Checked all diodes ... OK
The short is still there !
Now my brain is shorted ... I need a pause ;-)
Cheers
supe...@libero.it says...
check the main bridge rect., and the big elctros for leak, you will need
a ESR Meter they ain't cheap. :-/
Moussa
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William R. Walsh
> here's a typical schematic
>
> http://www.pavouk.org/hw/en_atxps.html
Hey! That could come in handy as the 335 watt Model 95 power supply uses a
TL494 controller as well. (For those wondering about this--I once sent one
of the supplies to Sam Goldwasser (author, editor of the
Sci.Electronics.Repair FAQ) and he said the "dead time control" pin on the
TL494 was being pulled high--and that it could be used as a shutdown method
in the event of a fault.)
I still have a few dead ones. All of them will charge their filter
capacitors (brief and minor dimming of the lights when plugged in) but they
do nothing when requested to power on. More often than not, they died after
a power failure, although a few quietly passed away while running.
I'd like to fix them, but I don't really have a lot of knowledge there and
working on high voltage, high current electronics puts me off a little bit.
William
Dr. Jim
> check the main bridge rect., and the big elctros for leak, you will need
> a ESR Meter they ain't cheap. :-/
But a basic ESR meter can be built very cheaply. Google for ESR meter
schematics, there are several out there.
-Jim
supervinx
replacement, marked BUX 85.
Someone still makes one ;-)
J. Clarke
Hope that marking isn't the price : )
supervinx
I didn't notice that BUX <-> Bucks !
Another language issue !
No, I've been asked 1Euro ... affordable to keep a 5160 original ;-)