After some waiting the vLA82 was back on stock and I ordered one. It finally arrived today after flying around the world.
I sadly couldn't find an original ULA
The result ist different together with the test RAM!
How ever it still doesn't function.
The border seems to be washed white now instead of green.
I'm still on the hunt to get this running. Anyone got more ideas?
Spectrum modded / composite question
Re: Spectrum modded / composite question
I haven't given up so far.
All caps are replaced with new ones same for transistor TR4 und TR5.
I also removed the upper from their sockets.
No change so far
All caps are replaced with new ones same for transistor TR4 und TR5.
I also removed the upper from their sockets.
No change so far
- 1024MAK
- Posts: 5302
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Spectrum modded / composite question
That photo in your last post, it looks to be failing the RAM check in the BASIC ROM. Hence the vertical red lines on a black paper (background).
The horizontal lines may indicate a problem with the address lines.
Did you get a diagnostic card or ROM?
Mark
The horizontal lines may indicate a problem with the address lines.
Did you get a diagnostic card or ROM?
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.
Re: Spectrum modded / composite question
I forgot.
Someone let me use a diag card.
It showed, that all RAM is broken. Sounds kinda weird to me, that ALL ICs are dead...
I also replaced the 7805
Someone let me use a diag card.
It showed, that all RAM is broken. Sounds kinda weird to me, that ALL ICs are dead...
I also replaced the 7805
- 1024MAK
- Posts: 5302
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Spectrum modded / composite question
Vsual check all address lines to/from the lower DRAM. If no problems are found, do continuity tests. Print out a copy of the schematic and use a coloured pen to mark each pin of each device as you test.
Then test for shorts.
If none of that finds the problem, try replacing IC3 or IC4.Yours
Mark
Then test for shorts.
If none of that finds the problem, try replacing IC3 or IC4.Yours
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.