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Re: ZX81 rebuild
Posted: Wed Dec 06, 2017 5:53 pm
by Paul
Lardo Boffin wrote: ↑Wed Dec 06, 2017 5:16 pm
Well, so long as they are polite!
I hope I wasn't unpolite.
Re: ZX81 rebuild
Posted: Wed Dec 06, 2017 5:54 pm
by Lardo Boffin
Paul wrote: ↑Wed Dec 06, 2017 5:53 pm
Lardo Boffin wrote: ↑Wed Dec 06, 2017 5:16 pm
Well, so long as they are polite!
I hope I wasn't unpolite.
No - you were very polite!
Re: ZX81 rebuild
Posted: Wed Dec 06, 2017 6:30 pm
by Paul
Lardo Boffin wrote: ↑Wed Dec 06, 2017 5:54 pm
No - you were very polite!
Thanks for the feedback, it's always hard to tell for me because I don't usually communicate in english
Re: ZX81 rebuild
Posted: Thu Dec 07, 2017 2:18 pm
by Lardo Boffin
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!
Re: ZX81 rebuild
Posted: Thu Dec 07, 2017 3:22 pm
by sirmorris
Did you change resistor values?
Re: ZX81 rebuild
Posted: Thu Dec 07, 2017 3:40 pm
by Lardo Boffin
sirmorris wrote: ↑Thu Dec 07, 2017 3:22 pm
Did you change resistor values?
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...
Re: ZX81 rebuild
Posted: Fri Dec 08, 2017 2:53 am
by 1024MAK
Don't Panic!
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...
You'll get there in the end
Mark
Re: ZX81 rebuild
Posted: Fri Dec 08, 2017 2:44 pm
by Lardo Boffin
1024MAK wrote: ↑Fri Dec 08, 2017 2:53 am
Don't Panic!
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...
You'll get there in the end
Mark
Its more stress than panic. This was supposed to be fun but has rapidly developed into a ‘mare.
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:-
- Results
- B72597C0-24F8-4BDB-8C69-5DD0C8867E40.jpeg (71.46 KiB) Viewed 4044 times
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.
Re: ZX81 rebuild
Posted: Fri Dec 08, 2017 4:18 pm
by gammaray
Its more stress than panic. This was supposed to be fun but has rapidly developed into a ‘mare.
That is why everything is called "work"!
"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."
Re: ZX81 rebuild
Posted: Sat Dec 09, 2017 12:54 am
by 1024MAK
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