Sinclair ZX80 / ZX81 / Z88 Forums

Hi I've got a couple of ZX81s that I'm looking to get running again. One has a very dark screen but you can see the cursor. I'm hoping this will improve with a video mod ? But the other I've already done a composite video mod on but the screen is completely blank. There are pots on the mod board but...

OK, understood

Thanks again Mark

Sorry - stupid question. Why the splitter cable ? My thought would be cable from Mic->Amp then another cable from Amp->PC LineIn (mic) - for saving And same cable reattached from PC speaker out -> Ear - for loading Also - is there definitely enough juice available to take it from somewhere on the sy...

Hi Mark

Certainly worth a punt at that price. Looks like it's coming from China so I might be waiting a while.

Will need to check what other cabling will be needed as well. Does this need a separate power source ?

Thanks

Thanks Mark On the subject of how to save programs. Does anyone know or think a small headphone amp might work to amplify the signal from the ZX81 enough for me to record the output on a pc ? I'd need to buy something but don't want to waste money if there's no chance of it working. e.g. something l...

Hi Since the results were obviously not as expected I decided to double check my homework. The upgrade involved running link wires from 4 of the RAM chip pins to 4 of the diodes at the bottom of the board. It looks like when I put the board back in the case and put things back together one of the wi...

Hi Running the program from XavSnap I go back to the return code 1/20 I thought I was getting previously, before the resets started. Don't know if this means an error on line 20 ? If I do a PRINT N after running the program I get a value of 17408 If I run the original program with a starting value o...

Hi Thanks for the replies Mark - if I change line 10 to what you suggest it looks like I still get a reset. So I tried a different value: FOR N=17700 TO 65536 STEP 256 This gives me a value back of - 13.535K Not sure what value I'd be expecting back ? It's obviously not 1K but don't know if there's ...

Hi I've recently got hold of a ZX81 to play with as this was my first home computer. I've done a composite mod and also added a memory upgrade internally to give 16MB without a Ram pack. Couple of things. Can anyone suggest a way to save programs without tape as I no longer have a tape recorder and ...