I hope I wasn't unpolite.
ZX81 rebuild
Re: ZX81 rebuild
In theory, there is no difference between theory and practice. But, in practice, there is.
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- Posts: 2235
- Joined: Sat Nov 26, 2016 2:42 am
Re: ZX81 rebuild
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Re: ZX81 rebuild
Thanks for the feedback, it's always hard to tell for me because I don't usually communicate in english
In theory, there is no difference between theory and practice. But, in practice, there is.
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- Posts: 2235
- Joined: Sat Nov 26, 2016 2:42 am
Re: ZX81 rebuild
Arrggghhhh!
The ZTX313s arrived today so I put them in (the right way round ), got a pulse and switched on.
I get a white screen and no K. Did I say argh?
The board was working - when I temporarily put the original TR2 back in earlier in the week I got a K. So I guess the question is - what have I broken while I was messing around? The ICs are Ok I think - I put them in another board and got a K.
Helllpppp!
The ZTX313s arrived today so I put them in (the right way round ), got a pulse and switched on.
I get a white screen and no K. Did I say argh?
The board was working - when I temporarily put the original TR2 back in earlier in the week I got a K. So I guess the question is - what have I broken while I was messing around? The ICs are Ok I think - I put them in another board and got a K.
Helllpppp!
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Re: ZX81 rebuild
Did you change resistor values?
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- Posts: 2235
- Joined: Sat Nov 26, 2016 2:42 am
Re: ZX81 rebuild
No - I left the original resistor in and removed the test ones.
The only thing I can think of is that I shorted something while soldering but cannot see anything.
I’m getting the same pulse on pin 6 of the Z80 on this board as another working one so it looks like that side of it is ok.
Edit - almost the same. The working board is pulsing and showing Lo at the same time. The non-working board is just pulsing. Not sure if that is significant.
Really wish I had left that ZTX313 in there...
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
- 1024MAK
- Posts: 5332
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX81 rebuild
Don't Panic!
Just start your fault finding investigation from the start...
Mark
Just start your fault finding investigation from the start...
- Test the +5V power rails
- Check for solder splashes using your eye (and maybe a magnifying glass)
- Test the Z80 CPU pins, A14, A15 plus /RESET, /MREQ etc...
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
Autumn is here. Bye bye summer 2024...
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
Autumn is here. Bye bye summer 2024...
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- Posts: 2235
- Joined: Sat Nov 26, 2016 2:42 am
Re: ZX81 rebuild
Its more stress than panic. This was supposed to be fun but has rapidly developed into a ‘mare.1024MAK wrote: ↑Fri Dec 08, 2017 2:53 am Don't Panic!
Just start your fault finding investigation from the start...You'll get there in the end
- Test the +5V power rails
- Check for solder splashes using your eye (and maybe a magnifying glass)
- Test the Z80 CPU pins, A14, A15 plus /RESET, /MREQ etc...
Mark
I have checked for solder with my eyes and a times 3 magnifiying glass (need a better one) and can’t see any. But that is not 100% proof.
Test results:-
There is always time for Excel! May extend that for all pins...
I do randomly sometimes get a pulse on A14 but not always. I never get a fast pulse on A15.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Re: ZX81 rebuild
That is why everything is called "work"!Its more stress than panic. This was supposed to be fun but has rapidly developed into a ‘mare.
"I have to work on something."
"i have to finish working on something."
"Something is not working, I have to work it."
"I am going to work."
"I wish that guy would work."
"I am tired of working on someone else's responsibilities."
"I am tired of repairing this, I wish it would work."
5-TS1000,UK ZX81<-Sheelagh, US ZX81, 2-TS1500/KDLX , 3-TS2040 printer, 2-TS2020 cassette decks, ZXPAND+AY, ZeddyNET, ZXBlast, UDG, ZX8CCB, AERCO, BUILDS/REPAIRS ZX Spectrum, ZX80 Minstrel, ZXMAX48 v1 v2, 2-TS-2068, ROM, 16kRAM
- 1024MAK
- Posts: 5332
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
Re: ZX81 rebuild
Don't Panic is a phrase on the cover of The Hitchhiker's Guide to the Galaxy...
Hence is the standard response to any situation...
Mark
Hence is the standard response to any situation...
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
Autumn is here. Bye bye summer 2024...
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
Autumn is here. Bye bye summer 2024...