I think my 6128's expansion port is bad :(

[blackdalek]

It's been months since I've had the Amstrad out to tinker with due to all the chaos going on everywhere. Anyway, my CPC's expansion port looks to be fine. All my other expansion devices seem to work fine - original multiface2, modern multiface2 for m4 board, the m4 board itself... however the Z-Mem card is still just causing random garbage and crashing whenever it is plugged in. Toggling the onboard settings switches makes no difference. I will try contacting Toto again, see what he thinks.

[blackdalek]

Well.... I've had the CPC in storage for past few years while raising my son and I really have not even had time to think about working on my cpc problem. He's almost 5 now so I think it's safe to get the cpc out again. 
I've just opened it up and checked the continuity of all the tracks i could see between expansion port and the components, then I also tested continuity of visible tracks from the z80 to other components.
I didn't find any broken traces
I still don't know why my expansion port doesn't work. Is anyone willing to give any other advice?
Can I post my cpc to someone who can fix it?

[Audronic]

@blackdalek 

Have you tried an other Z80
as most of the lines go directly to the Z80

Just a thought

Ray

[blackdalek]

@blackdalek

Have you tried an other Z80
as most of the lines go directly to the Z80

Yes. You actually mailed me one to test with back in 2018 and we had no luck with that either.

[Audronic]

@blackdalek 

I have just repaired a CPC6128, one of the symptoms was a clicking RELAY.
Which is one of your symptoms in the first post.

After testing 20 Ram chips purchased from china and found 14 (FOURTEEN) FAULTY.
I replaced the ram chips that were on the mother board that were faulty with some good ones.
This also stopped the RELAY from clicking.
Perhaps it was an intermittent short in one of the faulty ram chips
Just a thought

Good luck

Keep Safe

Ray

[blackdalek]

Perhaps it was an intermittent short in one of the faulty ram chips

Just a thought

Sounds plausible. How would I test for that?

Cheers,
Fraser

[Audronic]

@blackdalek 

As you have an M4, can you put Noels Diags into it and run it 
and let it do the longer test
I don't use an M4 but I am sure somebody can help

Kep Safe

Ray

[blackdalek]

@Audronic thanks for the tip.
I found and downloaded Noel's diagnostic program.
With only the M4 board connected, the long "soak" test ran without any errors for 53 iterations before I quit it.
I made several attempts to run it with the z-mem board attached but it was impossible. CPC crashed spectacularly within 3 seconds every time. Random screen garbage, tape relay clicking, disc drive motors starting etc.

[blackdalek]

I made some short videos of the CPC Diagnostics test running.
First video shows the CPC with only the M4 board connected. The soak test runs normally forever until aborted by user.

 

[blackdalek]

Next video shows affects of running upper RAM test with Z-Mem board attached.

[blackdalek]

and once more... This time with nice error bars screen at end.