Search found 6 matches

by Ian13
Fri Aug 11, 2017 5:22 pm
Forum: WANTED
Topic: ZX81 ULA wanted
Replies: 10
Views: 9458

Re: ZX81 ULA wanted

I was looking at the thread about a modern ULA thats drops in, sounds promising. Mine is not responding the the keypad, other than that it seems to work.I get the Inverse 'K' on the screen. runs bloody hot those. I have re-soldered all of the IC pins and it made no difference. I may consider getting...
by Ian13
Thu Aug 10, 2017 7:05 pm
Forum: WANTED
Topic: ZX81 ULA wanted
Replies: 10
Views: 9458

ZX81 ULA wanted

Before I decide what to do with my 'half dead' ZX81,(see my post in Hardware) does anyone know if there are currently 'any' responsibly priced ULA's available in the UK?

Thanks

Ian
by Ian13
Sat Aug 05, 2017 2:02 pm
Forum: Hardware
Topic: My ZX81 is not respondiung to Keypad
Replies: 4
Views: 2135

Re: My ZX81 is not respondiung to Keypad

Thanks.

I will see if there is any activity on all the ULA keypad pins, and check for dry joints. Dry joints can certainly cause problems on old PCB's

I will resolder all of the ULA and Processor pins, The ROM and the RAM must be working for it get the 'K' on the screen.
by Ian13
Thu Aug 03, 2017 6:28 pm
Forum: Hardware
Topic: Unknown 18-pin ULA chip
Replies: 10
Views: 4733

Re: Unknown 18-pin ULA chip

It could be the ULA out of the 16K Ram pack, mine has one.. not that it is working. no -5volts
by Ian13
Thu Aug 03, 2017 6:18 pm
Forum: Hardware
Topic: My ZX81 is not respondiung to Keypad
Replies: 4
Views: 2135

Re: My ZX81 is not respondiung to Keypad

Should my 'K' be flashing, it has been a long time since I last used it?

mine is not

That may explain why The keypad is not responding!!!!!

Any pointers.

Thanks.
by Ian13
Thu Aug 03, 2017 6:02 pm
Forum: Hardware
Topic: My ZX81 is not respondiung to Keypad
Replies: 4
Views: 2135

My ZX81 is not respondiung to Keypad

Hi, I am new to this forum, so excuse me if this question has already been answered before. I have an issue 3 ZX81, i have bypassed the TV modulator so I can use it with a PC monitor connected through a Composite video to VGA converter. I get the 'K' cursor on the screen, so signs of life. I have ju...