Powermac 5500 logic board issue... fail to boot.

[Schmoburger]

So I have a Powermac 5500... in fact I have a few of them. But this one in particular is a 5500/250 in black.

The issue is however, that it will not boot up with it's original logic board in it... It powers on but the screen will not flash up nor does it appear to do anything else of consequence. My first 5500/225 did this after a few years of nonstop operation, and it got relegated to a spares pile as it'd been replaced by my G3 tower anyway.

As the black one is somewhat of a rarity tho, I decided to not give up so easily, so I put the logic board out of another working 225 I had into it, and hey presto, it worked again!

So, the question is, has anybody else experienced this issue, and if so, has anybody been able to successfully repair it? I'd really like to get the original logic board with the 250mhz CPU operational again, rather than making do with the 225 as it devalues it and doesnt seem right having the slower processor regardless. :-/

My chances of getting a replacement board are pretty close to buckleys I think, as 5500's and parts for them are thin on the ground at the best of times in 2013, and 250/275 models are near non-existent, and worth a bomb... there is one, and only one currently on eBay.au at the moment going for in excess of $250 with 7 bids and 3 days to go, if that gives some indication. 8-o

 

[Macdrone]

Caps ? Did you replace them yet? I think those are best suspect and it will probably start working again. Also pull the battery if its old.

 

[Schmoburger]

Havent pulled anything off the board thus far... died before I had ever considered caps to be an issue. I guess that's probably the information I was jonesing for Was wondering if there was any specific cap or set of caps that is prone to failing on these particular boards.

As for battery, fairly certain i tried it without and also replaced it at one stage, but cant hurt to try again i guess.

 

[JRL1511844959]

My PM 5500 has the exact same symptoms - even with a 6400 board. I'm 95% sure it's the caps on the analog board that need repair.

 

[Schmoburger]

I know the 5260 (similar design but with 14" screen) were prone to FBT and analogue board cap failure, so it's possible. In my case I used the known good 225 logic board out of the crappier looking of my two regular beige 5500s tho and it booted up just fine and to my knowledge, still boots up (tho its been a few years since it was fired up last). Never took the opportunity to test out my first beige one with a different board, as by the time it died it was just milling away in my admin team corner at school not doing much. That one also had a terrible fan noise as well... Havent tried the 250 board in another working chassis. may do that sometime just to see what happens.

 

[alantoner]

Have you done all of the standard troubleshooting so far (swap ram/cache, pull expansion cards, zap pram)?