Spectrum Computing

Hi
I am trying to get the speaker working on my ZX Spectrum 48K Issue 3, at the moment i have 12 volts coming to the collector of transistor TR7 could anyone with a working machine check this for me as the schematics all state that this should be 5 volts.

Thanks Pintglass

The schematic is incorrect. I think the feed comes from the +9V rail (which can be as high as 12V). This applies from the issue 3 boards onwards.

See the issue 5 or the issue 6A schematics.

Mark

Hi
Thanks for the reply mark
Could you or anyone else tell me the correct voltage that is suppose to come from ULA pin 28
I get about 0.269 V when inactive and after i run a BEEP command in a loop I get about 0.7 from pin 28 upto the diode before TR7, I get about 0.548 V on the base of TR7 and 0 V at the speaker

Thanks Pintglass