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.
Harlequin 128K 2D not showing any video signal
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Re: Harlequin 128K 2D not showing any video signal
I’ve moved your post to the Sinclair ZX Spectrum Hardware section.
Mark
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
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ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
![Exclamation :!:](./images/smilies/icon_exclaim.gif)
Looking forward to summer later in the year.
Re: Harlequin 128K 2D not showing any video signal
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)
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Last edited by Tiger on Sat Sep 18, 2021 10:55 pm, edited 1 time in total.
Re: Harlequin 128K 2D not showing any video signal
It was a dry pin on U24. After soldering it the computer started working. Thanks!
Re: Harlequin 128K 2D not showing any video signal
Thank you for the feedback ![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)