Sinclair ZX80 / ZX81 / Z88 Forums

Hi,

I'm fighting with a 6U : no sound on the AY chip.
Everything is working, 128k games are running, but no sound .
Keyboard klick and beeper sound works fine.

I have replaced the ULA, the ROM and the AY ( from 100% working device ) , still the same.

Checked the AY pin1 ( analog C ) with a simple test program on a working and on this non working speccy, looks the output is different.
Working:
https://youtu.be/5q1a06ZbnSk

Not Working:
https://youtu.be/gfHAUPlBIvc

https://youtu.be/jaTgQVv6EOU

Also interesting, on the AY test pin I have nice square signal, but on the non working one.

Any idea what to check?

Thanks!

Check if 1.79MHz clock coming to the PSG.