Minimal boot config is always a good thing to try, as is verifying that all the jumpers are set to something sensible (particularly if there is a suspicion that the machine might have had a memory upgrade board at some point).
So is Tricky's test ROM (which covers some memory tests without actually needing to use the memory to do so).
For no sound, it's worth checking the negative rail is present (-5V), also if you stick a finger (or equivalent, but the human body makes quite a good antenna...) on one of the unused audio inputs (R11 from the 1MHz bus, or say R30 from the speech chip) you ought to hear some mains hum. There is also a volume control (VR1) to check.
It's also worth noting that the initial beep is the sound chip (IC18) powering up in a random state, with emphasis on the word random, prior to the OS booting and shutting it up. You could therefore have a coincidentally duff sound chip, or you could have no clock (generated at IC43 at 16MHz, then though IC40 to the video ULA which divides it down to the rates used by everything else). Chasing the faster clocks needs an oscilloscope (a cheap or old one will do), as these are too quick even for a logic probe. If you have a logic probe, though, that should be able to see presence of the slower clocks (1MHz/2MHz) from which you can deduce that the faster ones must be there.
So is Tricky's test ROM (which covers some memory tests without actually needing to use the memory to do so).
For no sound, it's worth checking the negative rail is present (-5V), also if you stick a finger (or equivalent, but the human body makes quite a good antenna...) on one of the unused audio inputs (R11 from the 1MHz bus, or say R30 from the speech chip) you ought to hear some mains hum. There is also a volume control (VR1) to check.
It's also worth noting that the initial beep is the sound chip (IC18) powering up in a random state, with emphasis on the word random, prior to the OS booting and shutting it up. You could therefore have a coincidentally duff sound chip, or you could have no clock (generated at IC43 at 16MHz, then though IC40 to the video ULA which divides it down to the rates used by everything else). Chasing the faster clocks needs an oscilloscope (a cheap or old one will do), as these are too quick even for a logic probe. If you have a logic probe, though, that should be able to see presence of the slower clocks (1MHz/2MHz) from which you can deduce that the faster ones must be there.
Statistics: Posted by wiggy — Tue Sep 10, 2024 10:27 pm