Re: lisa 2 startup problems

Hello,

I just did a quick recheck of the COP chip. I have 5.3 V between pin 1 and 9, pin 1 is truly connected to ground (3 ohm - could be because of the wires of the multimeter) and pin 4 is not hold reset (+5.3V) further the oscillator is working correctly. I suppose the COP chip is dead although there might be other problems (interrupted traces) on the motherboard and/or IO Board.

Could there also be some other kind of connection between the COP chip and the CPU? I think of some sort of inter-conditioning of the start up like the COP chip would only turn on the LISA when it gets a "ready" message from the CPU board. Does the Lisa power supply start without CPU board? If there is some sort of connection between COP and CPU board at start-up time I could lead this back on problems with the motherboard and would not classify the COP chip as being bad.

I would appreciate it if somebody could test if the power-supply of a LISA would start (power button light goes on) without CPU board this could really help me a step further. I would also be interested in buying functioning a LISA 2/5 motherboard because mine probably suffered from corrosion.

thank you!
Alex

joi, 1 noiembrie 2012, 21:35:39 UTC+2, Alex a scris:
>
> Hello all,
>
> I recently acquired a Lisa 2 (Macintosh XL) with the 2/5 motherboard, old
> IO board with the coprocessor socket and battery pack and 800k Floppy ROM,
> CPU board with ROM's dated 1985 and 2 x 512k RAM cards. The problem is, it
> won't start. The motherboard was badly corroded but I cleaned the corrosion
> with vinegar and alcohol and it looks decent now, I could not find any
> broken circuits.
>
> What I already tested:
> - Power supply is OK (+5V standby voltage present, replaced all
> electrolytic capacitors)
> - on the COP421 chip I can measure the power button signal when I press
> the power button but the state of pin 24 remains the same
> - i can "force" start the power supply by applying 5V on the ON pin of the
> COP421 (pin 24).
> - the power supply starts with no problems, correct voltages present on
> the I/O board
>
> - I can only get a grey picture with some horizontal lines but no sound
> and no video
> - unfortunately I have no other boards to switch out for testing.
>
> - does anybody have a clue where to start digging for reparing this lisa?
>

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