Sinclair ZX80 / ZX81 / Z88 Forums

I have a Memotech 16K RAM pack up for sale. As you can see the connector is somewhat broken! £10 plus p&p (UK preferred due to the hassle of selling abroad now). It may be that this works if you replace the connector but I have no idea. I suspect it is best used as an original ZXPand case or a repla...

I have a FileSixty keyboard for sale for £15 plus p&p (UK preferable due to the pain that it now is sending stuff abroad). I have given this a gentle wipe over and pressed all of the keys on a zeddy and all worked. Not sure what glue you need to use to stick this on! If interested please post on her...

A cell from a de-capped 2c184 ULA, the second picture is a cell with the overlay from Sinclair. I've had one or two that partially failed, membrane keyboard presses causing a crash but with a Memotech plugged in all ok. Replacement of the ULA cured it so not a board fault. Great photos! I have ‘The...

Moggy wrote: ↑Fri Mar 01, 2024 11:19 pm

Lardo Boffin wrote: ↑Fri Mar 01, 2024 8:58 pm Guess the program!


IMG_5789.jpeg


Running through the ChromaSCART.

10 PRINT "HELLO WORLD"
20 GOTO 10

Close but not quite enough letters! It is

10 PRINT “HELLO SINCLAIR ZX WORLD”

The ULA is, if I understand correctly, basically a collection of logic gates in one chip, so it's possible for it to partially fail without completely breaking down... if that makes sense. That does make sense - I have some ‘danger ULAs’ that are part failed that I keep for test purposes. It doesn’...

I put a different ULA in and it works perfectly. Put the old one in and back to Venusian.

Any ideas how a ULA could do this? Given that it pretty much works fine when a RAM pack / Spand is plugged in?

Guess the program!


Running through the ChromaSCART.

The ROM is really quite hot to the touch.

In the spirit of quick checks I have plugged in my ChromaSCART. With the onboard RAM switched off I get the display issue. With the onboard RAM switched on I still get the display issue. I was expecting it to work properly with the RAM on as this is in effect the same situation as having a RAM pack ...

I recall, along time ago, that I had a similar problem and replacing the voltage regulator fixed the problem. I got this idea from a forum posting but I can't find it. Not being a hardware guy I have no idea why the voltage regulator would garble the display, but replacing it worked for me. Regards...