Sinclair ZX80 / ZX81 / Z88 Forums

Oh how I wished I'd bought up the stock when I saw them

(C;

I've got a spare (working) Issue One board with a 2C184E if it's of any use? All ICs socketed Think I have the case too but it was heat damaged from what I recall, and don't think keyboard worked.

I may have another spare ZX81 too. Let me know.

Cheers,

Chad

It's the later ULA I wanted - I have working boards but no way to display them

The picture is just about viewable on an old composite monitor I have here but no TV will work with them.

Thanks!

C

I'm not convinced on the whole old ULA = dark/ new ULA = bright picture thing. I've got a 2C184 in one of my machines which gives me a cracking picture via composite video on both a CRT and LCD TV. Then I can swap in a 2C184 from another machine and the picture's almost black.

There's always the back porch mod using an LM1881 described in these forums somewhere. Wasn't there also a plug-in replacement engineered on an FPGA?

Regards,

Chad

Please describe the ULA chip or chips to me as they apply to each of the Sinclair family of machines, Timex included please. I am looking at a chip that has (c)Sinclair 1982 above (c)Timex 1983 with numbers-8334A 812200..some 201's..most are regular chip material , but one has a porcelin base and a gold square in the middle with..M8331 812200 same Sinclair above timex writing. Are these ULA chips? There are some that are square with little gold contacts on all 4 sides of the chip, the writing saysTimex 1500 PT 609-0380485 f707715 usa. the base looks whit, I assume porcelin. most are black square chip with f807207 usa. I seeTimex 2000 PT 609-0380784 f707892 usa , some NCRf808979 8345d Is this a ULA from the Timex 2068 of Portugal? Thanks in advance, I am trying to identify some chips.

Hi Neil.

ULAs are 40 pin plastic packages - there's a thread elsewhere dealing with the identifying numbers.

The other chips you have don't sound like anything you'd find inside a ZX81/TS1000.

Could you please snap some pictures?

THanks!
C

Chad wrote:I'm not convinced on the whole old ULA = dark/ new ULA = bright picture thing. I've got a 2C184 in one of my machines which gives me a cracking picture via composite video on both a CRT and LCD TV. Then I can swap in a 2C184 from another machine and the picture's almost black.

There's always the back porch mod using an LM1881 described in these forums somewhere. Wasn't there also a plug-in replacement engineered on an FPGA?

Regards,

Chad

Although there is still no replacement ULA readily available, we have of course, now released ZXvid, which provides composite video out and also fixes the back porch problem ! See viewtopic.php?t=628