This a ZX Spectrum Clone I built using this PCB https://github.com/DonSuperfo/Superfo-Harlequin-128

Partial copy of my post on Superfo Harlequin 128 facebook group:

So I also build a HARLEQUIN 128 Issue 4B. Already tested bunch of stuff and everything works great!

The first thing to mention is the problem I had with U13 (74HC04), there is some compatibility issue with using Texas Instruments IC SN74HC04N.

I assembled the PCBs and RGB cable, connected to CRT and it does not output anything, got a black screen (there was some noise on TV OSD and that’s it). Started troubleshooting and eventually came to oscillator powered by U13. The frequency was very much off. I first replaced the oscillator component itself, but it did not helped (the frequency though changed, but still wrong). Then I remembered reading on this FB group that someone had similar issue and they replaced U13 with older variant of the same TI chip. Since I could not source older variant, I found a Korean manufactured alternative (TAEJIN TECHNOLOGY). So I ordered this alternative chip and also another from TI from my local vendor. Previously all components were from Digikey. First I tested with TI and it failed in the same manner, it is maybe worth of note that TI chip fails consistenty, that is the frequency it produces does not change. Then I placed the Korean alternative and I got the Diagrom screen with beautiful RGB, it was such a relief… Don Superfo since I’m at least second person having problems with U13 TI IC I would suggest mentioning in BOM about this potential issue.

Failed IC: https://www.digikey.com/…/texas…/SN74HC04N/277212

Working IC: https://www.tme.eu/…/taejin-technology-htc-korea/74hc04n/

For the case I 3D printed The Mechtrum (https://www.printables.com/model/1186755-the-mechtrum) by leejsmith. It took me a bit of work with a knife and pliers to properly fit 4B PCB there. The keyboard tray also did not fit standard 16×16 switches, but leejsmith provided me with a step file and I fixed it. I send him modified tray file back, but he is not responding since May 31… Overall I like the case. I even added M2 size hot inserts so I can easily disassemble case multiple times without damaging some plastic threads.

I made an RGB cable using ScartPCB (https://github.com/screwbreaker/ScartPCB) and VGA cable. ScartPCB maybe a bit overkill for such a simple cable, but it is so convenient, I loved it. The Mini-DIN-9 soldering on the other hand was pain, I managed to solder pins on the wrong side first time… So I was very excited when I saw RGB working good.

DivIDE_AY – https://lotharek.pl/productdetail.php?id=319