working 6s crash with diag rom

[1024MAK]

If you want to minimise the risk to the board, and don't have a desoldering station, you could cut each pin, then once the chip body is out of the way, it's easier to remove each pin individually.

Mark

[amateus]

If you want to minimise the risk to the board, and don't have a desoldering station, you could cut each pin, then once the chip body is out of the way, it's easier to remove each pin individually.

Mark

Yes that's an alternative but I would like to retain the chip working. After all it's almost fully working, it's just the M1 line is missing. I can use it to test other dodgy units for example.

Btw, Mark, where do you buy your ICs? I used to buy at retroleum, but import fees to EU are rather prohibitive now.

[redgatemodels]

How's this?

https://www.sellmyretro.com/offer/detai ... -48k-25951

[Paul]

Or this?
https://www.reichelt.de/z80-microprozes ... 23029.html

[1024MAK]

Yeah, Zilog still manufacture the CMOS versions. So any company that carries Zilog products should be able to sell you one.

The CMOS Z80 should work in most ZX Spectrums.

The last Z80 that I bought came from RS Components I think. But I would have bought it at the trade counter (shop) in the nearest city to me in the U.K.

Mark

[amateus]

Thanks for the information guys, I'll buy one.

[amateus]

Quick update on this. Interesting one tbh.

I have removed the faulty Z80 and the M1 line is recovered.

Result:
DivMMC now works. Diagnostics ROM still has problems, symptoms are pretty much the same.

Short story:
Diagnostics card work correctly without the ROM chip installed. If I test with any known good ROM chip installed, never works.

Long Story:
After a lot of fiddling and continuity checks, I've decided to remove the ROM chip, install a socket and use a diag chip I have from retroleum. Work done, Diag chip run ok. I left him running for some time, all good, no errors
I inserted the diagnostics card and again the same problem. I've tested with other ROMS I have with no luck.
I then decided to try running the diagnostics card without any ROM installed and surprise surprise, it worked.


So, definitely something is going on in the ROM area. While the unit works fine and reports no errors when I run the diagnostics (whether from the diagnostic card without ROM chip, or from Retroleum diagnostic ROM chip), it crashes if I try to use both.

Any ideas?

Thanks,
Antonio

[redgatemodels]

No expert, but I'd be leaning towards a problem with the diag card. Does the Retroleum ROM run in the diag card?

[amateus]

No expert, but I'd be leaning towards a problem with the diag card. Does the Retroleum ROM run in the diag card?

So, not excluding any issue with the card, but it works on all other units, a mix of 48k and 128k, I have

[redgatemodels]

hmmm, very odd indeed. Bit like my Issue 2 weird colours problem, it's maddening tracking down what the problems are sometimes.