One more CPC 6128 with screen of death

[Kris]

Hi all,


I have this CPC with strange behaviour: I have a blue screen and black border at boot and the relay is switching ON.
I launch the RAMtest.bin program using my M4 board and got the attached result:


Can RAM issue explain the action of the relay ?

[Bryce]

Yes, it could. If the damaged RAM is holding an address or databit high or low (Stuck bit), then this could also alter the data coming from the Firmware ROM and can create false commands going to the CPU or enabling addressed hardware (like the 8255 which is controlling that relay).

However... a damaged CPU or ROM could also give the same results and look like the RAM is damaged too. So try a good CPU first (as it's socketed) and also check whether anything else is getting hot.


Bryce.

[Kris]

I already tried with an other Z80: same results.


I will let it run a while and check if a chip become more hot than other...

[Bryce]

I just realised from the photo that Geralds RAM program ran, which would suggest that the data and address lines are most likely ok. In that case, I'd start by replacing the RAM. Do you know what caused the CPC to fail?

Bryce.

[Kris]

NO idea, nothing special happened last time I used it...


I have let it run and nothing become hot, I compare with an other CPC and I got similar temperature.
I will check with a scope if I can see something different on RAM (I only have 6 chip of 4164-10 here and some sockets, I won't be able to change all of them)

[gerald]

You can also try to boot on the 2nd bank.
http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/need-some-help-fixing-cpc6128-not-booting/msg75204/#msg75204

[gerald]

You can also try to boot on the 2nd bank.
http://www.cpcwiki.eu/forum/amstrad-cpc-hardware/need-some-help-fixing-cpc6128-not-booting/msg75204/#msg75204

Forget the idea, I've just noticed that's a pre-asic one. No PAL 

[Kris]

CRTC 4 indeed


Finally, I have no more RAM....I ordered them, have to wait now...

[gerald]

CRTC 4 indeed


Finally, I have no more RAM....I ordered them, have to wait now...

BTW, you can use the same RAM as the one in a plus (64kx4), it could be cheaper.