Sinclair ZX80 / ZX81 / Z88 Forums

Hi,

I'm after an issue 3 board in any condition with or without case

Thanks Andy

I'm pretty sure I can sort you out Andy.

I'll check tonight. Any particular colour, sir?

sirmorris wrote:I'm pretty sure I can sort you out Andy.

I'll check tonight. Any particular colour, sir?

Careful Charlie not all issue 3s were red early ones were still green

Doh now i kearn that there where 2 different colours !

@SirMorris, no any colour will do, just decided it's about time i extended my collection of Zeddies and what better way than to get a issue 3 board, since as all mine are issue 1's

Regards Andy

I now have a question for owners of issue 3 boards.

does any of your boards have an extra resistor solder from the right side of C6 (above the CPU) ?

Thanks Andy

Yes my issue3 zx81 have that resistor.

Me too. It's 1k resistor connecting C6 / X1 (quarz oscillator) to ground.

PokeMon wrote:Me too. It's 1k resistor connecting C6 / X1 (quarz oscillator) to ground.

Quartz or ceramic resonator ?

reason i ask it the oscillator circuit i am using in the Replacment ULA did not work until i disconnected this ' extra ' resitor, Which is not present on the issue 1 boards.

I shal have a tinker with the circiut and see if it can be altered to work with both.

Andy

ceramic resonator ...

You can place a resonator on your "ULA replacement board" I think and forget the resonator on the issue one or issue 3 board ...
It's not used for something else, so why not build the oscillator on your ULA ?
The ULA is the boss of the clock ...