Hi All,
So picked up an Eight Ball Champ 1985 yesterday. Have fixed about 20 different faults from playfield, flippers through to the CPU faults etc. The last thing was the sound board (SB). Got it fixed last night to the point where all sounds and speech is working fine but there is a loud hum on the speaker. The SB has had it's capacitors replaced before apart from a couple of 2uf ones.
I put in another SB from my Eight Ball Deluxe LE and the hum is gone so definitely the SB.
I swapped over from the good board the 2uf old caps that hadn't been replaced but no difference.
I have hung the board off the chassis but no difference.
I swapped the 5v transistor (heat sink) as they were different on both boards so just wanted to make sure it wasn't that but no difference.
I re-replaced the large caps but no difference
The speech and sound small Pots are working fine
The door Pot is working fine (cleaned and lubricated anyway) but as the fault is on the SB no real worries here
Volume goes up and down as it should with all pots
Resoldered the header pins and checked the earth connection
But this ?$$!!!£$^&** Hum will not go away.....
Any ideas???