Print Page - One more CPC 6128 with screen of death

Title: One more CPC 6128 with screen of death
Post by: Kris on 11:26, 12 June 19

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 ?

Title: Re: One more CPC 6128 with screen of death
Post by: Bryce on 12:02, 12 June 19

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.

Title: Re: One more CPC 6128 with screen of death
Post by: Kris on 12:06, 12 June 19

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...

Title: Re: One more CPC 6128 with screen of death
Post by: Bryce on 12:30, 12 June 19

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.

Title: Re: One more CPC 6128 with screen of death
Post by: Kris on 12:34, 12 June 19

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)

Title: Re: One more CPC 6128 with screen of death
Post by: gerald on 16:15, 12 June 19

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

Title: Re: One more CPC 6128 with screen of death
Post by: gerald on 16:22, 12 June 19

Quote from: gerald on 16:15, 12 June 19
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 (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 ;D

Title: Re: One more CPC 6128 with screen of death
Post by: Kris on 20:07, 12 June 19

CRTC 4 indeed ;)

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

Title: Re: One more CPC 6128 with screen of death
Post by: gerald on 20:18, 12 June 19

Quote from: Kris on 20:07, 12 June 19
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.

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General Category => Technical support - Hardware related => Topic started by: Kris on 11:26, 12 June 19