TS 1000 artifacts after warming up

Discussions about Sinclair ZX80 and ZX81 Hardware
Moggy
Posts: 2030
Joined: Wed Jun 18, 2008 2:00 pm

Re: TS 1000 artifacts after warming up

Post by Moggy »

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
Posts: 8
Joined: Sat May 04, 2019 12:07 am

Re: TS 1000 artifacts after warming up

Post by embpic »

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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Joined: Fri May 09, 2008 2:48 pm

Re: TS 1000 artifacts after warming up

Post by Andy Rea »

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
AFK

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Andy Rea
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Re: TS 1000 artifacts after warming up

Post by Andy Rea »

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.
AFK

embpic
Posts: 8
Joined: Sat May 04, 2019 12:07 am

Re: TS 1000 artifacts after warming up

Post by embpic »

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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