Sinclair ZX80 / ZX81 / Z88 Forums

Hello,

I built the 48K version a few years ago and it worked like a charm.
Now it was time to build the 128K version but strange enough I get no video through the composite output. (I have no RGB cable to test).

I checked the voltage of the Z80 and it looks fine (5v) but it seems more related to the video circuit which I have no clue why it's not working.

Any help is very much appreciated.

Thanks in advance!

H.

I’ve moved your post to the Sinclair ZX Spectrum Hardware section.

Mark

Meanwhile I've built three Harlequin 128K 2D. There are much soldering points at the pcb and little mistake can result in a problem as you described. First I would check all the soldering connections. Are the jumpers correctly set? Is there absolutely no signal on your Monitor (still as not connected)? Is there a signal when you crap the signal direct from C28? Also there could be a problem with the AD724 (U48) proof the connection of this SMD part. I bought a pcb with a presoldered SMD but one connection of it wasn't good, so I had to resolder it (a very tricky thing because I've no special SMD-equipment) .

It was a dry pin on U24. After soldering it the computer started working. Thanks!

Thank you for the feedback