Powermac 7500/100 boot/video problems

[drawkcab]

Hi. I have a 7500/100 that that has recently had a problem starting. Pushing the power button does give power (green light comes on and I can hear the fan blow and some initial sounds). However, no video shows up on the monitor, and it does not proceed into the start-up process (i.e. I can't hear the hard drive spinning).

I thought at first my problem was the monitor, as it has had problems in the past. However, several weeks ago I moved the computer to another desk and plugged in a different monitor, and it started up without a problem. When I moved it back to the original place, the old monitor worked fine as well, and it started up again without a problem.

Today, I had the problem again (no video and no boot). I tried it with multiple monitors with no success. I have been researching online and have a few theories, but would appreciate any insight you might have.

Theory 1 - the internal SCSI cable came loose so the hard drive/ system is loose - which is why moving it may have jarred the cable enough for the connection to occur. I will check this tonight.

Theory 2 - the PRAM battery is dead. Several sites mention this for video loss. Not sure if this would impact the abilty of the computer to start-up, though.

Theory 4 - the monitor is not being detected. However, I don't think this would prevent the computer from starting up.

Theory 4- hardware failure of sometype - motherboard, hard drive, ???

Any ideas or suggestions would be appreciated.

 

[jimbopalmer]

I beleive you would get video even when SCSI is dead, I did

Radio Shack sell the battery as 23-026 a 3.6v 850mAh Lithium battery

throwing in a video card could test theory 4

I tried to remain child-like, all I acheived was childish.

 

[PTmon]

Jimbopalmer is right, it would boot without a scsi connection. You would get a flashing ? if the scsi is out, as the mac would boot but not be able to find a system.

If your pram battery is dead, then yes, it can prevent booting. Usually you will have had warnings on boot-up that your system clock is not set correctly. Even if you reset it, it will not keep it and you'd keep getting that error message. OWC has pram batteries real cheap if there's not a radio shack close by.

I'd definately crack the case and check connections. Also try zapping the pram.
Best of luck,
PT

http://mahon.homeip.net/remember

 

[drawkcab]

Thanks for the suggestions.

I checked the cables and replaced the battery, with no success. It is doing the same thing - pushing the power get a few seconds of activity (I think it is the hard drive moving after all), then everything stops. There is no video signal whatsoever (the little light on monitor stays orange rather than turning green).

I tried to boot it from a CD with no luck - the CD doesn't even start to spin. I am stumped on this one. Unless anyone has another ideas (which I would welcome), I am considering finding another computer in hopes of salvaging the hard drive.