Hi there,

all voltages are OK (including the negative one, I've found it).

Checked the EPROMs and the PROM. They are being addressed correctly, and I can 'see' output data.

I think I'm very close to solving this... there might just be some kind of problem with the onboard RAM :-o...

Hi,

All address lines on the RAM, near the CPU are high (5V). So I guess one of those two is defective.

Decided I'll sell the parts.

A few final questions:

Can the (E)PROMs be used in a KN-3000? Can the hard drive be used in a KN-3000 (does it have the same connectors on the CPU board)?

Is the display compatible with other models?

Thanks again!

yes to all, but the display only on a 3000/3500, the eproms will be needed to install a hard drive but will work on a 3000. Hard drive is the same and should just slot into a standard 3000, unless you have the Keysoft extension system. This required an entirely new HD board with delicate wires soldered onto surface mount pads on the main board using a magnifying glass, and a new wiring harness fitted, and gave all the functions of the 5000 HD system with Techmanager pc communication and a parallel port where the HD cover was. I must have been the only person in the country with one of those at the time