Performa 460 not starting

[Hancock]

Hi everybody,

I received recently a P460. The sender affirms that it was working fine before it was sent off, but she is not expert and her statements are not very precise.

Last thing she said she did was replacing the dead battery and taking out the harddisk.

Starting the Mac here: no chime, no floppy is accessed, no video - nothing.

The PSU is ok, power is supplied correctly, the fan is working.

My assumption is that the PRAM and clock chip is not working-

A reason could be that the sender has set the battery in the wrong sense - could this cause such a damage?

And more important: if this was the case, can it be fixed?

Again: no visible leakages and the board is clean.

Thanks in advance

 

[Hancock]

Update:

Yesterday I checked the FPU clock pin (socket) with my scope: The 33MHz clock speed signal is is available and proper.

Then the CPU also receive the clock speed signal and should be running.

Next I will check /HALT and /BERR 

Is it then correct to assume that the PRAM is ok and my initial concern was wrong?

Thanks for any feedback.

 

[bibilit]

Capacitors have been replaced ?

Also, the Egret chip can do that. 

 

[Hancock]

Hi bibilit,

I have not yet down anything with the Mac - as said when I took it out of the parcel it was refusing any cooperation.

So I have not seen the Mac running.

The board looks neat and clean, and the sender confirms (more or less precisely - that the Mac was working before she sent if off.

In the worst case she sold a "dead" Mac - then I have to review my assumptions and start working from scratch.

"Also, the Egret chip can do that." - what does this mean?

From another thread I had the impression that the PRAM/RTC-"module" must be properly working before the MCU is kind of started; the schematics seem to confirm that.

So if I see 33MHz at the MCU/FPU-pin then the MCU/FPU should be running fine?

Rgds

 

[bibilit]

a chip responsible for kicking the system. This chip is present in most Logic boards of this era, unfortunately close to the capacitors and very often contaminated. 

Solved a lot of issues removing and cleaning this area. 

You can already clean the board and try again 

 

[Hancock]

Ok, this link is helpful, thanks.

Apparently I have to have a much closer look on the board.

So far I was assuming that the transport or the replacement of battery were the cause of the issue.