Sinclair ZX80 / ZX81 / Z88 Forums

I followed the instructions from Retro revival shop where I bought it from

Photo attached

Before you get too carried away... The 1N4148 should have its number written on it. You may need a good light and a magnifying glass to see the number though. The zener diode should also have either part of its number written on it, Or the voltage (5V1). What voltages do you get across these capaci...

Just a quick update I tested TR4 and TR5.
Following the guide on markmorton.co.uk,

TR4 tests ok
TR5 tests ok for negative on base 0.6v on both outside legs
TR5 test with positive on base shows open circuit in collector correctly but 0.6v on emitter, not the 1.2v expected

Hi all. Bit if a story with an issue 3B board I was working on Replaced all electronic capacitors, tested ok Replaced modulator with s-video mod tested ok Replaced 7805 with a murata regulator and did the 4 lower ram jailbar capacitors tested and ok Then finally I decided to do the DC-DC mod and tha...

Thanks Mark

Hi,
I have a working issue 3 48k board and a non-working issue 2 board. Is it ok to test the issue 2 ULA 5C112E in the issue 3 board to check it is working. I have a dandanator to run the zx diagnostics

Thanks Mark

Thanks Mark, so it looks normal under no load to have 11.3v on pin 16 of scart? I'm using an RGB cable designed for the 128k+ and purchased from well known maker of cables on eBay. The problem is my RGB hdmi scart converter failed recently while the 128k+ connected. I just get a black screen now fro...

Having a bit of bother on toastrack 6K. I've removed the composite signal to pin 1 and attached a wire with 75 ohm to the center pin of the RF modulator output. Composite works correctly. I've checked the voltages on pin 1 after the mod and I am now getting 11.3V and struggling to work out why - sur...