ZX Spectrum 48K Mainboard Issue 4S - Help!
Posted: Tue Aug 24, 2021 6:03 pm
Hi,
Firstly I'd like to say that this is my first post other than my introduction, so please bear with me. I was recently given a ZX Spectrum + which was in a terrible state, but as I've been thinking about buying one from a well-known auction site I thought this would be a 'free-hit', meaning it might not cost too much to get into a working state.
The case, keys, membrane were all completely ruined so my thinking was to remove the mainboard, see if it works and then get some 'rubber key' replica/custom parts to fit it into. Upon initial inspection, there are some pretty major issues with it and one in particular is completely baffling, so I'll show you that first.
1. Z80 CPU missing
I've never seen this before. Whoever previously owned this appears to have desoldered the Z80 from the board and installed some naked pins in its place, badly. I'm looking for some advice on what to do next with this (if anything).
Here is the rear of the board. Hopefully you can see what I mean here, I've boxed the pins that have been soldered in place of the CPU.
2. ULA missing
I'm told that the ULAs for this board aren't commercially produced anymore, so I'm looking for some advice.
3. Ceramic capacitors bent/flattened
Looks as if the previous owner squashed some of these during their repair attempts. Any advice on whether these are still likely to work would be great.
So, in a nutshell my guess is that this project could cost me a bundle just to get into a testable state. Any advice welcome and certainly regarding the CPU. I've never heard of a removable/changeable Z80 CPU that would cradle onto pins in that way, so I'm totally baffled by it. Is it even worth trying to get this board into a working state or am I better off buying one from auction?
Cheers,
Mike
Firstly I'd like to say that this is my first post other than my introduction, so please bear with me. I was recently given a ZX Spectrum + which was in a terrible state, but as I've been thinking about buying one from a well-known auction site I thought this would be a 'free-hit', meaning it might not cost too much to get into a working state.
The case, keys, membrane were all completely ruined so my thinking was to remove the mainboard, see if it works and then get some 'rubber key' replica/custom parts to fit it into. Upon initial inspection, there are some pretty major issues with it and one in particular is completely baffling, so I'll show you that first.
1. Z80 CPU missing
I've never seen this before. Whoever previously owned this appears to have desoldered the Z80 from the board and installed some naked pins in its place, badly. I'm looking for some advice on what to do next with this (if anything).
Here is the rear of the board. Hopefully you can see what I mean here, I've boxed the pins that have been soldered in place of the CPU.
2. ULA missing
I'm told that the ULAs for this board aren't commercially produced anymore, so I'm looking for some advice.
3. Ceramic capacitors bent/flattened
Looks as if the previous owner squashed some of these during their repair attempts. Any advice on whether these are still likely to work would be great.
So, in a nutshell my guess is that this project could cost me a bundle just to get into a testable state. Any advice welcome and certainly regarding the CPU. I've never heard of a removable/changeable Z80 CPU that would cradle onto pins in that way, so I'm totally baffled by it. Is it even worth trying to get this board into a working state or am I better off buying one from auction?
Cheers,
Mike