Black Knight Sound Board Repair

brypten

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The sound and speech were working intermittently during gameplay of Black Knight. It would start to work a little, then stop.

When I pushed the self test, all sounds would work.

I swapped the cpu and driver with a known working set and same symptoms, intermittent sound.

I changed C27 which on my sound board was a 4700uF 16V cap with a 6800uF 16V cap (all I had) and it seemed to fix the problem. Ran for 6+ hours last evening/night with no problems and then turned on this morning with no problems.

I am still going to order some more caps as I should replace more on that board.

Feels good to get that game working 100% again
 
Don't forget that the sound board is a fully independent processor set from the main CPU board. On a System 7 like Black Knight, the input signals all come from a dedicated PIA on the CPU board, nothing comes through the driver board. And a bad CPU/Driver board PIA tends to lock up the whole game.

My first guess from your symptoms would have been connectors, those IDC connectors after 30 years are just junk and I can't tell you how many cracked header pins I see. Out of curiosity, what made you suspect that capacitor? That's the main filter cap for the sound board CPU, so it's a good idea to replace it either way. On older sound boards of the same design they used a much larger cap, so that size you used will be fine.

If the problem comes back, do the connectors on the sound board next.

-Hans
 
Don't forget that the sound board is a fully independent processor set from the main CPU board. On a System 7 like Black Knight, the input signals all come from a dedicated PIA on the CPU board, nothing comes through the driver board. And a bad CPU/Driver board PIA tends to lock up the whole game.

My first guess from your symptoms would have been connectors, those IDC connectors after 30 years are just junk and I can't tell you how many cracked header pins I see. Out of curiosity, what made you suspect that capacitor? That's the main filter cap for the sound board CPU, so it's a good idea to replace it either way. On older sound boards of the same design they used a much larger cap, so that size you used will be fine.

If the problem comes back, do the connectors on the sound board next.

-Hans

I have already replaced most connectors in the backbox. To be honest, it was the only cap that I could replace! Sometimes you get lucky...
 
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