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
ZX Spectrum 48K speaker issue
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Re: ZX Spectrum 48K speaker issue
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
See the issue 5 or the issue 6A schematics.
Mark
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“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: ZX Spectrum 48K speaker issue
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
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