Sinclair ZX80 / ZX81 / Z88 Forums

Have a look here:
https://forum.tlienhard.com/phpBB3/view ... 739#p43739
It is designed for the ZX Spectrum, but it would be easy to adapt it to the ZX81. The advantage: It is programmable, so you can play even all games which are designed only for keyboard use.

The command makes sense, the result of the printing is only displayed when the boolean result from the USR call is true, which it is when BC >0. However the PRINT itself wil print nothing even when BC >0, the ; will keep the cursor on the same line and not to the next line. Your problem is differen...

LET A=USR 30000 or PRINT “” AND USR 30000; This doesn't solve my problem really. First point is that ( "" AND USR 30000) is not an admissible expression. The first term is a string, the second a number, and AND is expecting numbers. But I want to go more in the details: The command under discussion...

I have a question concerning MC on ZX80. Suppose, I have poked a RET ($C9) at address 30000. The command PRINT USR(30000) will come back with 30000. But I want to surpress the printing. How can I drop the PRINT instruction from the stack?
Is there good textbook for MC programming on ZX80?

Hello Matthew, nice project. Do you have a spare PCB for me? It would be interesting to compare your board with our recent construction (rune and me) which can be found in https://forum.tlienhard.com/phpBB3/viewtopic.php?p=45188#p45188 The address decoding is much poorer than yours, but the filterin...

Interesting project. What about the software? Will it be as powerful as the CurrahµSpeech software?

As already mentioned by MAK1024 the signal level at the MIC connector is much much smaller than a "line out level" of temporary voice recorders. It is just 5mV in contrast to 200mV for the last mentioned. Make sure you have the right equipment for that.

gseb wrote: ↑Thu Jul 02, 2020 12:15 am 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....

Could you try with an original PSU? Cause of 9V<10.8V, the instructed minimum for 4116.

Hi,
it is more reliably to check the -5V at pin1 of the RAMs. Some Memotech RAM don't generate the 12V but use instead of the 9V from the power supply. If the -5V is missing, you have to repair something. First check.

SHZ88 wrote: ↑Thu Jun 25, 2020 9:18 pm The image does appear to change, whenever I press on the PCB or "fiddle" with the power input.

Check the voltage during "fiddeling" with your meter. Is it stable? Sometimes the power connector has dry or broken joint. Use a magnifier glass.
Heinz