Vulcan IIgs Power Supply Repair

[Polymorph <mike.a.stephens@gmail.com>]

Hi all,

I recently acquired a Vulcan IIgs which was originally working. However, 
shortly after getting it, the fan died. I replaced the fan with a spare 
one I had lying around, but after I had fitted the new fan, the power 
supply stopped working. It repeatedly turns on and off really quickly. I 
believe this is normal behaviour if no load is detected, but I have 
tried it with or without plugging it into the IIgs' motherboard socket 
and it behaves the same way. The motherboard power light flashes on and 
off repeatedly. This sounds very reminiscent of a problem Antoine had 
mentioned with his //e in 2009 
(https://groups.google.com/d/topic/comp.sys.apple2/Hc95ZUUC8gI/discussion) 
- which funnily enough I commented that I hadn't seen that behaviour 
before!. I should also mention I have since removed the fan in question 
- not that I think it should cause any problems (it is rated similarly 
to the original), but I've been wrong before.

I replaced the 2 large 150uF 250V capacitors thinking it to be the 
likely failure point, but it hasn't made any difference. I have done 
this before in other power supplies and have had good results. This time 
it appears to be something else...

Anyhow, should I just continue to replace the other electrolytic 
capacitors, or is there something specific I can do to troubleshoot the 
problem? Are there any other likely components likely to fail?

I'll probably continue to replace the capacitors, but if anyone can 
offer a better suggestion I'm all ears. I could replace the internals, 
but I'd really like to get the original supply working again if possible.

Any help would be most appreciated.

--

Cheers,
Mike

Find my Apple II projects online at:
http://apple2.sytes.net/