Sinclair ZX80 / ZX81 / Z88 Forums

So quite some time passed, but finally got some time to work a bit on this zx81 and like to share an update. I've tried with the original power supply, linear regulated - works fine but no noticeable improvement vs my switching Chinese PSU... actually checked with oscilloscope the power output of th...

Thank you Mark clear now, let me see what I can do... So this picture is the TV output, the image is a bit blurry, greyish and there are very visible jailbars. Its not horrible but the TV sometimes loses sync or does not sync when powering on (if I try a couple of times it works). Note: I'm using a ...

Hi I did get a very bad and noisy picture on the RF before trying to apply the mod. I didn't spend too much time with that because I thought my PAL TV wasn't tuning well with a very old SECAM output (I just used to test the computer was actually booting). I can confirm that I have a 2c210e ula (date...

Hi Mark, Yes I did try to lift the D9 zener as a good measure I also removed entirely the 2n2369 and lifted R29, but the signal does not change. I also tried your circuit: didn't know it was yours :D I've just found it on the internet. It actually seem to give the best results, it seems to be the mo...

Hi All, I have recently acquired a SECAM ZX81. It works, but my LCD TV does a terrible job with SECAM standard so I decided to do composite mod and I am a bit puzzled by it... the unit has the SECAM additional components, a zener in D9, a 1kohm resistor in R32 and a 2n2369 transistor with collector ...

Hi everyone, thanks for letting me join this group. I grew up in the 80s with Commodore machines and only recently I've decided to explore the other side of the 8bits: I've acquired a couple of ZX spectrums and one ZX81 all mostly working (some problems on the ZX81 for which I will open a thread) an...