Issue 3 Spectrum vertical red stripes

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
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BlackFX
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Issue 3 Spectrum vertical red stripes

Post 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?

Image

Thanks!
PootisSpencer
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Re: Issue 3 Spectrum vertical red stripes

Post by PootisSpencer »

Looks like upper ram. I had the same with mine.
BlackFX
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Re: Issue 3 Spectrum vertical red stripes

Post by BlackFX »

Unfortunately it behaves the same with the upper ram gone.
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Ast A. Moore
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Re: Issue 3 Spectrum vertical red stripes

Post by Ast A. Moore »

1. Check all the data and address lines for shorts/continuity.
2. Replace the ROM.
Every man should plant a tree, build a house, and write a ZX Spectrum game.

Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
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1024MAK
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Re: Issue 3 Spectrum vertical red stripes

Post by 1024MAK »

It could still be a problem with the lower RAM or a fault on the CPU address lines.

Mark
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BlackFX
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Re: Issue 3 Spectrum vertical red stripes

Post by BlackFX »

So I put diagRom on an eeprom and now this happens

Posted in the order it occurrs. So CPU is alive but something tells me it's almost dead

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1024MAK
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Re: Issue 3 Spectrum vertical red stripes

Post 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
:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :dance
Looking forward to summer later in the year.
BlackFX
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Re: Issue 3 Spectrum vertical red stripes

Post 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
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1024MAK
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Re: Issue 3 Spectrum vertical red stripes

Post by 1024MAK »

You may want to try using the ZX Spectrum Diagnostics and see if that can help.

Mark
:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :dance
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Re: Issue 3 Spectrum vertical red stripes

Post by BlackFX »

A0 on the ULA was shorted to ground...
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