Sinclair ZX80 / ZX81 / Z88 Forums

After some waiting the vLA82 was back on stock and I ordered one. It finally arrived today after flying around the world. I sadly couldn't find an original ULA :( The result ist different together with the test RAM! How ever it still doesn't function. The border seems to be washed white now instead ...

Thank you for the very detailed info and explanation!

Voltages seem to be ok then and temperature too.

I also measured the DRAM Voltages. They (-5V, +5V, +12V) are okay. Can one assume that the power supply is working as intended?

Current output

I recieved the DRAM 4116 replacement chips today. At least they tested fine. I installed one of the them to have a full set of 8 chips. It still doesn't work. How ever the screen output looks different now. I let it run for a couple minutes and the only chip that got warmer and warmer was the ULA. I...

The missing parts for the DIY DRAM tester came today.
Only one chip didn't pass the tests. Time to get a replacement for it.
I assume it's not possible to run the machine with just 7 chips to check if there are more broken parts?

DRAM faults are more common, but ULA chips do occasionally fail. I'll try that first. Desoldering was easy using a heat gun. I never did that before. I'm quiet amazed lol. Sockets are already laying on my bench. So fixing stuff like that in the future will be easier. In case one or more of the chip...

If you hear the key click sounds and BASIC appears to be running (try SAVE "P" ), then it's more likely to be a ULA fault rather than a DRAM fault. But without a test/diagnostic ROM or another ULA to swap with, it's hard to be certain. Mark Hopefully it's the RAM. ULAs seem harder to come by. I cer...

Does the border always turn white at every power on? Do this (power cycle waiting 30 seconds in between) at least five times. If yes, the Z80 and ROM are likely okay, Border stays white all the time Press down on the ULA (IC1) to make sure all pins are making good contact with the socket (assuming ...

I just hooked the device to my TV. My TV does not have a composite input anymore, that's why I'm using the same hardware setup I use for my retro consoles. Composite -> Koryuu -> Component -> GBS Control -> VGA -> HDMI converter -> TV The output seems to be garbage tho. Key presses however change th...

The 100µF 16V electrolytic capacitor is going to go outside the case of the modulator. Now feed through the negative lead (the lead next to the - minus markings) of the 100µF 16V electrolytic capacitor through the spare left hand plastic hole in the modulator so that it goes to the centre pin of th...

Hello, my dad recently took me into his basement to show off some old stuff. He bought a Sinclair Spectrum back in the early 80s and modded the shit out of it. His words were. The original keyboard was crap, I had to do something about it. He basically took some old keyboard and used this behemoth a...