Weird CPC664 Fault

[Audronic]

Hi all 

I am Having problems with a CPC664 Motherboard repair.
I was wondering if you may have struck this before.
Can you Help

This is using Geralds WIP Tester

Thanks Keep safe 

Ray

03 9 397 7695 In Williamstown Victoria

[Audronic]

A small update.

Boot up screen is Unwell
The top line should say "AWA" not Isp ?

Any thoughts ?

Thanks

Kep safe

Ray

[GUNHED]

A bug in the firmeware ROM?

[eto]

Maybe a malfunctioning CRTC or broken traces from CRTC to the multiplexers. 

How did you start Geralds RAM test? From ROM? Can you also try LLopis' Amstrad Diagnostics?

[Audronic]

A bug in the firmeware ROM?

Hi Gunhed

Ok Thanks

I have changed the 40015 rom and this has helped
About an Hour later only a Blank screen Grrrrrrr

I am about to change the Gate Array and see what happens.

Thanks

keep Safe

Ray

[Audronic]

Maybe a malfunctioning CRTC or broken traces from CRTC to the multiplexers.

How did you start Geralds RAM test? From ROM? Can you also try LLopis' Amstrad Diagnostics?

Hi Eto

I Have a lower rom board with Geralds and Noels Diags - Switchable..

Thanks I will buzz out the lines from the CRTC  to the Mux's

Keep Safe

Ray

[Brocky]

i think one of the lines on the mux's has failed...
i dont think a buzz out will help... better off lookin at the lines on a scope if ya have one...the physical connection could be fine but one of the chips is outputting bad signal on a line

im not sure about geralds diag... but on noels, if you get a memory error you should be able to track down which ram chip thats 'failing' is connected to which mux chip
(i know ya can with geralds too but.. i not sure what numbers correspond to which ram chip)

[Audronic]

i think one of the lines on the mux's has failed...
i dont think a buzz out will help... better off lookin at the lines on a scope if ya have one...the physical connection could be fine but one of the chips is outputting bad signal on a line

im not sure about geralds diag... but on noels, if you get a memory error you should be able to track down which ram chip thats 'failing' is connected to which mux chip
(i know ya can with geralds too but.. i not sure what numbers correspond to which ram chip)

HI Brocky

Ok I am half way thru testing the continuity, I will keep going to Pin 40 from the CPU to all pins connected to where ever.
Yes I have a scope will do that next.

Ok Noels Diag gives Me 1 Beep (HI) goes thru the Memory test, screen changes to Blue and 3 LOW Beeps and that's it ??

Thanks

Keep Safe

Ray

[Audronic]

Hi Brocky

Have tested all the pins from the Z80 to what it is connected to all Test OK

I will look at the Mux chips with the scope

Thanks

Here is a copy of the Test points for a CPC664
From the Z80 to wherever.

Keep Safe

Ray

[eto]

I have changed the 40015 rom and this has helped
About an Hour later only a Blank screen Grrrrrrr

Did it fully work after changing the ROM? 

Is it blank grey screen with black border now or just a black screen?