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
- 1024MAK
- Posts: 5118
- Joined: Mon Sep 26, 2011 10:56 am
- Location: Looking forward to summer in Somerset, UK...
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
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
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) .
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