Sinclair ZX80 / ZX81 / Z88 Forums

Or was a U.K. model partly modified... Can you please confirm what TV / video picture standard it’s producing? And which type of modulator is or was fitted? It looks like there are only 3 differences (compared to UK boards:) ULA, color burst crystal, DC jack. Perhaps this is a prototype or a pilot ...

I got some interesting news about my 5C114E ZX Spectrum. According to the person I got it from, my ZX came in a box full of Sinclair related products, mostly TS1000 and TS2068 machines. The box was removed during cleanup from server room of some company located in Middlebury, CT. Well, Timex's HQ wa...

Replaced 14.000MHz crystal with 14.112MHz, added 51R resistor on the output (to get rid of reflection,) replaced C25 and C65, made some color adjustments, and here are the results: IMG_9608.jpg Still not perfect, but my LCD monitor could be the problem here. Picture on my large screen TV is better t...

Yes, moire pattern is caused by the phone. Power supply has the simple mod and I will replace all caps later on. I may also swap 14MHz crystal with the one from 2068 just to see if there's any improvement.

Fixed the power supply and everything works, however, the color and quality of the image is pretty bad. It could be that my new generation TV doesn't like Spectrum's signal that much or that I need to replace 14MHz crystal with 14.112 (which can be found in 2068) and make some adjustments with trim ...

Test ROM reports bad RAM and possibly ULA and multiplexer chips. I would prefer to eliminate ULA as a suspect before I start replacing other chips.

EDIT: after more testing, it turns out the PS is bad. ULA is good, woot, woot!

Hey @bola_dor, I have a Spectrum with 5C11E ULA, which appears to be bad. I am not sure if someone was trying to convert PAL Spectrum to NTSC Spectrum or if this thing is original (it looks original.) If you are willing to sell one or two of your ULAs, I could try to make it work and if it does, I c...

Thank you for your answer.
Yes, it appears this board was fixed at some point, it has the latest ULA (6C001E-7,) which unfortunately is bad, D5 pin is not working

I was going to create a new thread, but my question is the same, just different board issue. I just got this early issue 2 board and there are several modifications that do not look like factory mods, rather messy. Are those needed? 1. C47 and C54 are gone 2. D15 was removed, 2 new diodes and 1 new ...

Captured all that's going on during boot up and everything looked fine. There are few weird reads/writes, but my working Spectrum does the same thing.
The next step was to replace the remaining five 4532 chips.
Well, everything works now! Awesome!