TS 1000 artifacts after warming up

Discussions about Sinclair ZX80 and ZX81 Hardware
Moggy
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Re: TS 1000 artifacts after warming up

Post by Moggy » Sat May 04, 2019 10:28 pm

The two inductors on the board would seem to confirm a US spec board as Mark says, even in the absence of the grounding strips common to this board.

embpic
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Re: TS 1000 artifacts after warming up

Post by embpic » Mon May 06, 2019 2:18 am

Yes, this is a US computer.

Andy is going to send me a new ULA. Hopefully it will solve the problem.

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Andy Rea
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Location: notts UK

Re: TS 1000 artifacts after warming up

Post by Andy Rea » Mon May 06, 2019 8:50 pm

Hi Again, yesterday i soak tested a ULA for over 3 hours and all is well it is been packed up now ready to wing its way over to you.

the commodore monitors work fine but do need the link on the ula shorting as they have a high impedance input on that composite input.

from the scope trace it does look like your are getting 2 h-syncs in very short space of time, which is very odd indeed and the onlt thing that can cause that is ~M1 and ~IORQ both going low at the same time and resetting the internal counter. i guess it could be a bad connection on either of these signals. Or but this is wildly speculative some Z80's were known to have a problem with weak M1 signals BUT since as a good M1 signal is requiered for the standard ULA to operate correctly this would seem to be a stupid suggestion but if the CPU's are socketed it could be worth trying a known good CPU.

sorry it's took so long for me to get on this thread have had a busy crazy weekend.

regards Andy
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

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Andy Rea
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Location: notts UK

Re: TS 1000 artifacts after warming up

Post by Andy Rea » Mon May 06, 2019 8:57 pm

Just one more thing.. the transistor composite mod inside the modulator housing... remove or bypasss it. thie signal from the ULA should go direct to the output socket on the modulator. it doesn't need buffering.

@Mark yes got a 26Mhz osc module on board... the really 2011 ULA i did had a sort of colpitts osc and was dodgy to say the least... so just went for this will work every-time approach.
6 x ZX81, 1 x TS1500 , 1 x +3e, 1 x timex 2040 printer, 1 x timex 2020 cassette deck, siclair printer and some spectrum

embpic
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Re: TS 1000 artifacts after warming up

Post by embpic » Tue May 07, 2019 5:44 am

Well I am not sure why but my Sinclair has decided to shape up and fly right. :D

I have had it running for several hours now with no problems. I really didn't do anything other than leave it on for quite a while and the artifacts stopped. I have let it cool down and start again with no issues. Really weird but I am glad it is working now.

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