Mac Quadra 950 Won't Run After Cleaning

[CC_333]

Hi,

I got a Quadra 950 a few months ago, and decided to clean it out.

So I did.

However, something seems to have killed it, as it won't start up. All I get is a momentary soft screeching sound from the power supply accompanied by a click from the speaker, and then it goes off. Holding down the keyboard power button (or turning the key switch to ON) causes it to cycle. 1 maybe 2 seconds of the soft screeching, a brief pause, repeat.

Is it dead for good, or is there something that can be done to resuscitate it?

c

 

[Byrd]

Have you tried the usual strip it down to known working parts - eg. minimal RAM, no cards, etc, etc, etc? Sounds like a short somewhere.

 

[CC_333]

Have you tried the usual strip it down to known working parts - eg. minimal RAM, no cards, etc, etc, etc?

Yes, I have. It never had any cards, but I stripped it down to the bare board essentially. No RAM, no nothing. It behaved the same way. This RAM is tested good in another machine, by the way.

Sounds like a short somewhere.

I agree. But what I'd like to know is why it's there, and how to fix it.
It's not the power supply itself, because if I disconnect it from the logic board in a certain way while it's doing it's thing, the power supply will fully engage and spin up the hard drive. I assume that means the power supply is OK, but who knows?

c

 

[spiceyokooko]

Was the machine working okay before you cleaned it?

It's hard to offer any suggestions because it could be so many different things. As a hunch check the key area thoroughly, make sure the correct key is inserted and its fully and correctly engaged, see if you can bypass the key altogether. I'm not that experienced on Q950's (I've never had one of my own) but we did have one where I worked and I know from experience that key could be temperamental.

Other than that I'd strip the machine again and put it back together making sure all the connectors are clean and correctly seated. I know it's obvious but mistakes do happen - I recently finished reassembling a Powerbook G4, plugged it and pressed the power button and nothing happened. I turned it over and realised I'd forgotten to plug the battery back in.

 

[CC_333]

Hi,

It was working fine before I disassembled it.

I took the CPU out of its socket. Is it possible a bent pin or something could be causing this?

I've stripped it down to minimum: power supply and logic board only with no key switch. I plugged in a keyboard so i could use that as a "power switch", and got the same results.

I will check the CPU and see if that's the culprit.

c

 

[CC_333]

It's Alive!!!

I pulled the CPU, and found that I put it in upside down! I straightened a bent pin which resulted from my mistake, put it in correctly, and the Quadra chimed once again!

So, thank you very much! I was almost certain it was a goner!!

c

 

[mcdermd]

That's some good luck! There's nothing more heart sinking than a pin that you find torn off the proc.

 

[CC_333]

Hi,

I know! I had an old Intel CPU on a board that I killed while doing a BIOS update, and a pin got bent somehow after I removed it. As I was trying to straighten the pin, it fell off.

Anyway, I was lucky! I am getting it reassembled, and I need to put some RAM back in so it'll boot (now that it actually can once again!)

c

 

[spiceyokooko]

Well done cc !

So pleased to hear the Q950 breathes again.

 

[uniserver]

i had a customer once that had a 486 that he broke a pin off, so what i did to fix the issue was, soldered a wire to the pad on the cpu and ran a wire all way around to the bottom of the main board, soldered the wire to the correct pin from the bottom of the zif,

 

[CC_333]

Hmm. Interesting.

I might give that a try sometime.

c