Sinclair ZX80 / ZX81 / Z88 Forums

Greet job. I'll use this.
Martin

Great article.

Martin

Are you sure it's the ULA at fault? I havn't measured the Lambda 8300 yet. 1st project is to get the ZX81 running again. May be possible to make an adaptor board to take a ZX81 ULA plus extra EPROM for the character patternss, plus its decoding circuit, also the Lambda has crude sound capabilities,...

mrtinb wrote:Looks like the manufacturer's name is RCL.

And the logo on the IC looks like the logo on this homepage: http://www.rcl.com.hk/

RWAP wrote:could the other Lambda owners check to see if they have a different ULA (maybe a manufacturer name!)

Looks like the manufacturer's name is RCL.

Martin

• NEC D780C is the Z80 CPU
• MN2114-3 is the RAM
• 2364CR01 is the ROM I assume
• C4005 2283 must be the Lambda's ULA

Martin

The clock output is on pin 14 (should be Pulsing signal, your results show it High). It is then inverted by a transistor and goes into the Z80 CPU on pin 6 (should be Pulsing signal, your results show it Low). Please retest. I've retested. Now ULA pin 14 is Low, and CPU pin 6 is High. Let's assume ...

ZX81 Bodo Wenzel ULA (DIY).

ZX81 2C210E ULA with Heatsink at Mutant Caterpillar Games (GBP 19.99).

ZX81 ULA Replacement by Andy (DIY).

Martin