Sinclair ZX80 / ZX81 / Z88 Forums

Hi all!

Hoping someone can help me with an issue to do with my ZXPand+. I got it nearly two years ago but it's taken me this long to get my act together and fit a composite mod to my ZX81.

As far as I can tell, the ZX81 works ok, I haven't tried to load anything into it but commands work.

However, when I execute any special command, like CONFIG "V" to see the version, the video goes off and never seems to come back on. CAT also seems to say 9/0 and be empty, and again if I try and do CAT ">GAMES" to change directory the video goes off again.

The firmware version is the latest, and it doesn't seem to matter if I have my 4GB SD card in or out. :/

Has anyone come across this before?

I wonder if it might be the SD card (is it a fake?) or possibly the edge connector on the ZX81 needs cleaning

As Rich (RWAP) suggests a nice clean edge connector always helps, I clean mine monthly and it really does make a difference.
I have 2 ZXspand + and the only time I get the code 9 error is when the card isn't seated correctly after I've taken it out to load a bunch of files from my PC and put it back into the ZXpand, so to make sure do a nice firm push home into the slot with power off then away you go kind of thing. The only qualifier to that is my firmware for the plus is slightly modified to incorporate certain MIDI/AY/SERIAL TO USB, gubbins but otherwise should be roughly the same as yours for all practical purposes.

I have five of the classic ZXpands of varying issue/firmware and they never seem to exhibit this condition so I can only assume it's an SD slot/firmware quirk of the plus version.

Also welcome to the forum Robeej and always feel free to ask the knowledgable folk here anything zeddy related and I think you will find them most obliging and welcoming.

Thank you both very much for your suggestions!

I've not cleaned the edge connector so I'll try that first as I'm pretty sure the card is genuine.

Also thank you for the nice welcome, I feel like I'm rediscovering the ZX81, it was my first computer all those years ago and where I first learnt some Z80 poking into 1 REM XXXXX.

Wow that edge connector was dirty! But cleaning it didn't seem to help. :/

I'm going to try the normal 16k rampac I have and see if I can load a program into it. Then maybe I have some idea if it's related to the ZXPand+ or not.

I guess there isn't a useful ZX81 utility program that checks RAM for errors or any other hardware bits? Not that it has a lot of hardware bits...

RAM test in BASIC

https://www.vintage-radio.net/forum/sho ... ostcount=5

To see how much RAM the Zeddy thinks it has... follow this link

The other way to test RAM is to use DIM to create an array that is suitably large. Fill it with data, then read it back.

See also here.

Mark

I tried the Memopak 16K initially, and initially BASIC said I had 1k, which is erm not good. Checked the connector with a meter and things were not connected, it was shifted over a bit so fixed that... then it said correctly 16k.

Put in the ZXPand+ again and it also said 16k.

Decided to then check every pin with a meter to make sure it was connected to the interface, one was open. This was ROMCS I think? It had a bit of dirt on it, something the PCB cleaning pen and isopropyl didn't remove, attacked it with a sharp bladed screwdriver using the scraping method.

Everything now works!

It was a dirty edge connector all along.

Thank you so much everyone for all your help! I'm now off to play demos and enjoy games I could never afford (lots of hires ones that I dreamed of trying) which all quickly got abandoned once I got a Speccy.

I might have to write a game for this thing that I first learned Z80 on.

I’m glad that you’re now up and running

Mark