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Issue 3 Spectrum vertical red stripes
Posted: Sun Jul 26, 2020 6:43 am
by BlackFX
Hi all
I am banging my head against the wall with this, I have an issue 3 that's showing a consistent white border with red stripes as in this pic - I've swapped all the lower ram and buzzed it all out with my meter checking for any broken traces. Any thoughts on where to go next?
Thanks!
Re: Issue 3 Spectrum vertical red stripes
Posted: Mon Jul 27, 2020 2:54 pm
by PootisSpencer
Looks like upper ram. I had the same with mine.
Re: Issue 3 Spectrum vertical red stripes
Posted: Mon Jul 27, 2020 9:44 pm
by BlackFX
Unfortunately it behaves the same with the upper ram gone.
Re: Issue 3 Spectrum vertical red stripes
Posted: Mon Jul 27, 2020 11:53 pm
by Ast A. Moore
1. Check all the data and address lines for shorts/continuity.
2. Replace the ROM.
Re: Issue 3 Spectrum vertical red stripes
Posted: Wed Jul 29, 2020 2:53 pm
by 1024MAK
It could still be a problem with the lower RAM or a fault on the CPU address lines.
Mark
Re: Issue 3 Spectrum vertical red stripes
Posted: Mon Aug 10, 2020 12:29 am
by BlackFX
Re: Issue 3 Spectrum vertical red stripes
Posted: Wed Aug 12, 2020 10:33 pm
by 1024MAK
Which diagnostic ROM are you using?
Run the diagnostic ROM on an emulator to see what it normally does, then compare to what your faulty Spectrum does.
I suspect either a short between two different address lines or a problem with one of the multiplexers (IC3 or IC4) but I could be wrong!
Mark
Re: Issue 3 Spectrum vertical red stripes
Posted: Thu Aug 13, 2020 11:30 am
by BlackFX
This is the ROM I'm running
http://blog.retroleum.co.uk/electronics ... -spectrum/
As you can see the splash screen is garbled
Re: Issue 3 Spectrum vertical red stripes
Posted: Tue Aug 18, 2020 8:04 pm
by 1024MAK
You may want to try using the
ZX Spectrum Diagnostics and see if that can help.
Mark
Re: Issue 3 Spectrum vertical red stripes
Posted: Thu Sep 24, 2020 12:33 am
by BlackFX
A0 on the ULA was shorted to ground...
