Sinclair ZX80 / ZX81 / Z88 Forums

Hourrra ! I still have to test but now the ZX81 boot with the 16Ko ram.... I do not know what hapened with this 16ko but the two LS157 were broken ! Lucky enough it's not the prom... Some more testing and I will do the mod for the 9V..... EDIT : The ZX81 also start with the 9V PSU and the 16K pack +...

Yes, I will but .... I wanted to be sure that the extension is working properly before to do the 9V modification..... So, I buit a adapter cable for the PSU from my +2. With this adapter, the original +2 PSU is working on the ZX81 and I have 11,6V on the ram. But the result is the same as with the 9...

Some news on my +2 grey..... I replaced all the capacitors included the one from the tape recorder. Replace some resistors with other one with other value to have better sound cohesion. Replace the old regulator with a traco. Also put a wire to join 2 GND surface on the tape recorder PCB, I 've seen...

Thank you very much for the very clear informations. I will try that and will report the result.

I do not have an original PSU, just one from +2 but not the plug to do an adapter. I took the way to build the Memotech PSU universel.... I removed all 4116 ram. I tested them all and they are all OK. I will keep them for something else. I will install 4164 (with the small hack to correct the pinout...

I have on the ram ICs : +4.95 V -4.65 V and about 9V (instead 12 v ?!?) My PSU is a modern 9V one, it output just 9V. This is working fine with a sinclair 16ko Pack though the sinclair one may generate the 12V differently.... MC14011B pin 14 (where should be 12V) is also connected to the ZX81 edge p...

I checked and the 12V is coming directly to the ram from an MC14011B pin 14....

Do you think I should replace it ? I think so as it is generating the 12V.

Thanks

Hello, I have a white screen with my Memotech 16K Ram pack. It's the only things connected to the ZX81, jumper are set for master. I have only 9V on pin 8 of the Ram ICs. As I understood, it should be around 12V..... Can someone tell me which part is producing the 12V ? This is probably the problem ...

Yes it is. Very interesting thread. The capacitor that has to be removed for better RGB was not present. This was already done... I understand now why I had from the start a good clear image on my LCD TV :D Just waiting for some resistors to correct the sounds level and parts to recap. After that, I...

Another problem... The Audio quality is realy poor... I have to set the TV volume almsot at the max to hear little bit of music. And I think due to the fact that the volume is at it max, there is lot of noise. In R-typ for exemple, when shooting and so, sound are OK but also with lot of noise.... Wh...