Sinclair ZX80 / ZX81 / Z88 Forums

Hi. I am trying to fix my Toastrack and ZX-Diag while testing lower ram shows "RAM FAIL 4" that maps to the IC10 on the board. So I will have to replace it. i can see that all of the 16 RAM chips on the board are of the same type: OKI M3764A-15, therefore I have the following questions: is it so tha...

I have socketed ULA back Tested ULA another working 48K, and it was OK. Then I put it back into non-working 48K and this time got black paper white border. But, I could run ZX-Diag properly this time. :? IC15.jpg then I replaced IC15 with the working one and it works ok now. tried a game, all looks ...

The supply to pin 13 goes via a resistor to reduce the supply voltage. Inside the chip, this goes to an internal voltage regulator circuit, which in turn supplies the logic circuitry. Hence around 3V is normal. Thanks, got it the R34 I have tested the neighbor pins for shorts and did not find any. ...

Thanks, Mark! The first thing I tried was to measure the voltage on pin 13 and pin 14. pin 13 gives 3V pin 14 gives 5V the working ZX gives 3V on pin 13 as well, so I assume it is OK, even if the doc says it should be 5V. ZX Spectrum ULA.png I will start with trace pinging, document it in a spreadsh...

Thanks for the reply! How did you remove the socket? Is there a possibility that one or more of the plated through holes was damaged? If yes, then you need to use a copy of the schematic and prove that each ULA pin connects to all the other nodes (chips, resistors, diodes or transistors) as shown on...

Hi. I need some help with the diagnostics of the Issue 2 ZX Spectrum 48K. After replacing the voltage regulator with 78S05 , and swapping the capacitors, I verified that it is working, and everything looked OK. After that, I decided to add the heatsink to the Ula. Ula was socketed, so there was not ...

Got it. So, no high temps and I can use pretty much any soft foam material to replace it with.
Thanks!

Hi everyone!

Recently bought a rubber 16 Spectrum and a Toastrack, both working, and manage to short to Toastrack while installing the stereo mod, so will be asking questions here trying to revive it.

Hello.

What is the purpose of this spacer on the Toastrack?


Does it have to withstand higher temperatures?

Thanks!

Thanks! I will continue using the original 12(?)V power supply. It was originally bought/sold in Sweden, and even though it looks like an original but it does not have any Sinclair markings on it. I also ordered a new power supply from byte delight for the toaster that did not have a power supply, s...