Just bought a Speccy off EBay. As far as I can tell it has not been opened before. The board is an issue 3B but it has a strange looking modification near the speaker which you can see in the photo. Doing a quick google shows that this is not standard on 3B boards. Does anyone know what it is or what it’s for?
Issue 3B board - what the heck is that?!
- 1024MAK
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Re: Issue 3B board - what the heck is that?!
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: Issue 3B board - what the heck is that?!
Thanks Mark, in your opinion was this done by the factory or by the owner? I am slightly concerned by the lack of solder in connection the top-right. I haven’t powered it up yet as I will need to perform a composite mod first.
Richard
Richard
- 1024MAK
- Posts: 5165
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Issue 3B board - what the heck is that?!
Is the connection you are concerned about soldered on the underside? If yes, it’s nothing to worry about, as the holes are plated-through connections, so the tracks on the top and bottom are electrically connected together.
It may have been done in the factory (most likely), or when the board was serviced or repaired by a professional.
Mark
It may have been done in the factory (most likely), or when the board was serviced or repaired by a professional.
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: Issue 3B board - what the heck is that?!
Yes, it seems to be soldered fine on the bottom. So I guess it's a good thing that it is has this mod even if it's a bit unsightly.
I did a quick test by holding the composite connector up against the wire that feeds the RF modulator and the case, and unfortunately I can see that I'm not getting the Sinclair Research text, so I suspect it has a lower RAM fault. I'll check that when I have some time.
I did a quick test by holding the composite connector up against the wire that feeds the RF modulator and the case, and unfortunately I can see that I'm not getting the Sinclair Research text, so I suspect it has a lower RAM fault. I'll check that when I have some time.
Re: Issue 3B board - what the heck is that?!
Update on this Speccy - there was indeed a lower RAM fault - I replaced IC7 and everything is looking good so far
- 1024MAK
- Posts: 5165
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: Issue 3B board - what the heck is that?!
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.