Help needed with Apple IIe Power Supply repair (ASTEC) [SOLVED]

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X5900's picture
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Help needed with Apple IIe Power Supply repair (ASTEC) [SOLVED]

[SOLVED]

After replacing all Caps including C7, I've reflowed every joint on the solder side of the PSU and it came back to life. The Apple IIe was a PAL version (820-0073-B) and showed following problems after repairing the PSU:

- no Power LED lit, no beep, PSU wasn't audible clicking -> Silence

Solution: Capacitor C17 and C15 shorted -> replaced C9, C12, C17 and C15 with 10µF 50V 85 electrolytic capacitors = board fully functional

Pictures

[SOLVED]

After reading David Finnigan's New Apple II User's Guide, I've decided to revieve my dad's old IIe. I remember, back when I was a kid, this was his most priced possession, quite litarally. I've grown up in the Russian occupied part of Germany and at this time in the 80's, computers - especially Apple II's - were pretty much not accessable for people or insanely expensive.

Anyways, I've kept the IIe safe and sound for about 23 years now, but after hitting the power switch a few days ago ... nothing, no beep, no power light, no board led. On the audible side of things: no chirping, no clicking either, just plain silence.

After a bit of reading, the culprit seemed to be the PSU and after initial testing of the board connector, all outputs measured 0 to 0.5 Volts. As I understand, the Astec PSU is an early switcher, but doesn't need a load on the outputs to get going?

At first visual inspection, the caps on the low voltage side seemed to be quite cooked over time, and with no ventilation in the PSU case, I don't wonder why. How it seems, if one of the caps would have failed, there should be only one or 2 rails missing, but not all of them. There are 2 RIFA filter caps next to the AC plug, which showed cracks in the casing but were not blown. The AC fuse was still intact. Looking at the board and the backside, no visible burn or scorch marks, no signs of cracked or cold solder joints anywhere. But because the caps are nearly 33 years old (IIe 1982), I decided to do a complete recap, all electrolytics and the RIFA's, too. Said and done, I triple checked every cap I've worked on and fired it up - still silence. Well, at least no smoke.

I've gone through all the usual repair tips listed here in the forum and on some other sites, but I cannot figure out whats wrong with it.

Here's the story so far:

- PSU: Astec AA11042B (699-0161-A, 240V-50Hz-0.5A-70W)

- no noise, chirping, buzzing etc. on power up, no smoke either

- visually checked components and boards, nothing unusual

- replaced all electrolytics with exact matching types, except C7 (listed as 220µF/10V, built in was 220µF/63V and replaced with 220µF/25V)

- replaced RIFA X2 line filters, 1x .1µF and 1x .47µF @ 250V/275V

- Fuse was/is intact

- L+N board connectors = 230VAC (Europe)

- Switch and Cord intact

- DB1 Bridge rectifier intact: 230VAC in, 330V out

- No output on board connector J14, Pins 3, 4, 5 and 6

- checked resistors and diodes for shorts, seemingly ok (could have missed some)

... For now, I'm a bit lost. Since all low lines are missing, my guess would be some fault in the PWM circuit? Honestly, I didn't want to test any further on a live psu without directions and knowing exactly what to look for.

A little help would be greatly appreciated!

PS: I don't want to switch PSU's or replace it with a modern ATX one, the IIe should stay the way it was when my dad used it. Otherwise there would already be an ATX inside Smile

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Re: Help needed with Apple IIe Power Supply repair (ASTEC)

Hello X5900,
first of all welcome to the community.

Next: maybe it´s a good idea to read the pages in my site related to the stuff:
http://www.appleii-box.de/appleboxallabotpowersupplies.htm
that page and the following pages explain some basic knowledge about how that supplies are working...

Next: There is a small mistake in your thoughts on measuring... the supply does need a load for correct operation !
In general i use clips to bring +5V, + 12 Volt and Ground to an old outdated harddisk.....
that´s good enough to ensure a relieble load to the supply.... to get correct measurements....

for the negativ supply rails no load is needed - they operate well if there is a load at the posittive rails....
besides: If you prefer german language we can handle the communication by pm´s here....
I´m located in Bavaria....

sincerely speedyG

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Re: Help needed with Apple IIe Power Supply repair (ASTEC)

Thanks speedyG,

excellent informations on your website, to be honest, I've read through all your pages before posting. Actually I've spent a lot of time researching and asking for help is kind of a last resort for me Smile ... But, after reading it again for an hour or so, I've started probing around again and behold, if I twist the board slightly on the secondary end, I could hear a chirp and all rails came back on. So I would assume it's a cold joint after all. The question now is where?

What parts could cause a complete shutdown of all positive and negative rails at once?

For the load or no load question, I'm not sure, I did research the psu quite a bit and came across this repair post:
http://www.nightfallcrew.com/15/09/2014/apple-iie-power-supply-repair/

That's why I've assumed there's no need for load.

Gruesse nach Bayern! Smile

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Re: Help needed with Apple IIe Power Supply repair (ASTEC)

Hello X5900,
most common for cold soldering joints are the heavy transformers.
Due to their weight they cause most power to their joints.
Anyhow, if you are not sure about the specific point i´d recommend to resolder all solderjoints at the
soldering side...
but beware of current load stored in the big electrolytioc capacitors....
i´d recommend to make attempt to the soldering iron and the PCB if the supply has been taken away from
powerin source at least 1 day.....

if resoldering you must not suck off the old solderinglead...
but it should at least get again fluid texture....
if you add a bit of new soldering material it might even be better....
depending to the age and probably unknown state of the previous storage -
there might have been in the meantime some corroding taking action to the joints...
( German term: Bleifraß ).....

and take care not to overheat the active devices like diodes, transsistors and IC´s.....
the rule : as much as needed to get fluid, the less as possible to protect from overheating !
then after that procedure repeat your measurement with load....
i guess at least part of the problem will have vanished...
speedyG

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Re: Help needed with Apple IIe Power Supply repair (ASTEC)

Well, good news, the supply now works perfectly with and without load. I've gone over every joint except the heatsinks. Thanks for the tips, speedyG!

Sadly, now the board wont start up. I guess more research incoming Sad

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Re: Help needed with Apple IIe Power Supply repair (ASTEC)

Look for open 100K or 150K resistors on the high voltage side of the power supply. Make sure you discharge the 2 large filter caps on the high voltage side first. I use a 60 watt light bulb in a socket wired to pigtails and temporarily place across each cap for a few seconds. You must make sure that the bulb is good as on open bulb won't discharge the cap and you could have a shock hazard. I just jump the bulb across 120VAC after I jump the caps, and if it lights I know that I safely discharged the caps. I absolutely agree with speedyG about the importance of a load for the supply to start and regulate properly. I also use an old hard drive wired to the +5, +12, and common. The reason for the old drive is to avoid any damage to the motherboard should the output voltages be too high. The negative 5 and 12 volt outputs are feed by 3 terminal regulators and do not need a load, but you should verify they are correct before you connect the motherboard.

Hope this helps,

Dick Stachowiak

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Re: Help needed with Apple IIe Power Supply repair (ASTEC)

Sadly, now the board wont start up. I guess more research incoming :(

Hello X5900,
Here are several threads as example how mainboard issues have been tracked down
containing a bunch of tips....
some also contain valuable links to books for download related to service....
and in case i shall join the tracking process also several threads also
have good examples of pictures taken for examinations...
speedyG

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