Sinclair ZX80 / ZX81 / Z88 Forums

Just a thought. Have you removed the firmware update from the SD, so it doesn't try to update at every boot?

Are you using the latest version of ZXpand Commander?

The only thing I can find in the manual is this, and it looks like you follow that: GETTING STARTED Most cards come pre-formatted. In the rare case this isn't true or you want a fresh start then you can format the card. You can use any of the standard FAT format types: 12, 16 and 32 are supported. W...

Maybe you can try if it is possible to format it as FAT32, and see if that changes anything.

I have only tried with 4 GB and 16 GB. I have never tried with small SD cards.

Do you format them with FAT12, FAT16 or FAT32?

Can you try different SDs?

I remember reading somewhere a newly formatted SD formatted with a dedicated SD program, and not just the formatter of Windows/macOS.

Make sure the files on the SD is no longer than 8.3. This limitation for the name of the SD card as well.

And try both FAT16 and FAT32.

Here is one on eBay, with the manual included.

https://www.ebay.com/itm/174717889305

Since the ULA is an IC which is a circuit shrunken down, I believe part of an IC can be broken.

I only have issue 3 PCBs, so that will ruin that theory.

The home built TZXduino I have, has no amplification. It just outputs 0V or 5V on the output pin to the ZX81 or Lambda 8300, and that works. If I measure the output from the TZXduino when playing a P-file, I get 2.5V which is the average of 0V and 5V. What is the average voltage on your TZXduino, wh...