The Sinclair QL Forum

The only niggles I have with DataServe Retro's replacement ZX81 keyboard membrane are that the keys are white rather than silver/grey and the keys are slightly too far towards the front by a mm or so, oh and it's very-very slightly (<1mm) too large back to front in places. Otherwise, it works well.

I managed to have a chat with Charles on Facebook and after a test he asked me to do it's confirmed that the CPLD is dead.

Anyway, it's alive with the original ULA...

OK, I've got it working with the original ULA. When I reseated the CPU last night I didn't notice that the /RD pin wasn't in the socket! I'm amazed that the machine worked at all! P.S. The vLA81 still doesn't work so I'll have to contact Charles. P.P.S. The keyboard membrane has finally failed too m...

With a original ULA, a white screen often means the Z80 is not running the ROM program (RAM fault, ROM fault or Z80 fault). In this case, you will not get all the proper sync pulses. Mark Ah, but the strange thing is that I'm getting the 'K' cursor but not the frame sync. The data and address buses...

OK, the input to the ULA on pin 35 is not looking good. I can see a small signal but it's hovering around the +5V mark. I wonder if R4 has died. This is supposed to be an 8K pull-down resistor for the clock. The clock on pin 14 is fine. P.S. It's actually supposed to be 18K (poor scan of the schemat...

I've always found the VLA's 100% reliable and I know Charlie makes sure each one works before sending it out. Has the VLA seen many hours of use? I hope it is something trivial like the socket causing grief! I assume the original ULA is a 184 type without the back porch (is that another term for en...

There aren't really many electrolytics on the ZX81 board and they're reliable 1970s/early 80s ones anyway. Most of them are ceramic caps. The voltages on the board are fine, about 4.85V on the +5V. The regulator's getting a bit warm as the PSU seems to be supplying 11V rather than 9V. Given that it ...

I brought it down from the loft to give it a check-out before the 40th anniversary in March, plugged it in and switched it on without the RAM pack and it worked for a few seconds and then the output signal disappeared. Swapping the vLA81 ULA replacement out and putting the original ULA at least got ...

The blue passports - are they still printed by a French company? Yes, and printed in Poland. And all the dead "happy" fish - there'll be a right old stink with that :twisted: Note that it's only fish who become happy and British if they swim into the UK waters and not humans... I wonder w...

(The UK is the only country to do this.) Apparently not, it is the result of an EU rule we inherited. EU makes any non EU country business do this now as well! Why is it that companies in the US and other places are now stopping exports to the UK then when they are still exporting to the EU and had...