Sinclair ZX80 / ZX81 / Z88 Forums

Hi Mark

Thanks for the advice on contacting ben versteeg, he was more than happy to email me the code file for the GAL, managed to source a new one from Lattice and blow the code onto it, works perfectly now, turned out to be a counterfeit chip from china.

Thanks again

Hi Mark

I bought it from Byte delight a few years back, I never thought about Ben being there. Thanks for the advice, I will contact them.

Kind regards
Simon

Hi all I have a standard Zx Spectrum 48k issue 4S running a DivMMC Enjoy, 2014 Version with Esxdos .085, both working fine until recently, then the spectrum would just randomly crash while playing a game, any game, usually goes back to Sinclair Research (Blah). Press the NMI button, and it would go ...

Hi Mark
The 4116s are STC 4116 2N type so 200ns if I recall, identical to the ones in my other working issue 2.

Hi all Sorry to be a pain with this board but it’s driving me insane. When I got this board it was in a pretty sorry state, I got a good ULA and I have a Diagnostic rom installed, all the voltages are in tolerance, but when it’s switched on, the diagnostic Rom does a lower ram test, the first time i...

Pins 13 and 14 are 4.98 volts, and hello, no activity on pin 32, checked the solder side and found a minute solder splash pulling it to ground, cleaned that off, hurrah! Activity, put the new ULA in and it lives again, well, limps a bit, some lower ram failure due to dodgy chip sockets (See photo), ...

Thanks Mark I found a list of which ULA went in what machine, and you are correct, although this ULA I believe is dead, I just get a black screen with white lines across it, like static, I have replaced the Video decoder (LM1889), the Z80, all DC-DC converter transistors, although all the voltages w...

Hi all Bought a Spectrum 48k issue 2 listed as not working, just come to renovate it and noticed they have put a 6C001E-7 ULA in the socket instead of the usual 5C112E, will this work without any other component change? I’m asking because I don't trust the repairs they did to the board, due to the f...

Sounds like TR7 (ZTX450) is the culprit, specially if the 5v line has gone high at some stage, this can happen if a lower ram chip has badly failed and spiked the 5v line, Ive not seen D9 fail before, but might be worth replacing if TR7 doesn't remedy it. And the standard speaker should read 40 Ohms.

1992 Sinclair Research Ltd? I suspect a hacked rom there