Tales of the Arabian Nights
Williams, 1996I installed new capacitors on the sound board because i had some interferrance in the sound and the DMD was showing some wavy lines so i was told that it would be a good thing to change out the capacitors.
I have double checked my work multiple times and all looks good but when i turn the game on it makes this incredible loud noise so something must be wrong.
Anyone knows what the problem could be ?
Quoted from BentleyBear:I installed new capacitors on the sound board because i had some interferrance in the sound and the DMD was showing some wavy lines so i was told that it would be a good thing to change out the capacitors.
The sound and DMC voltage sections of the board are two completely separate circuits that have only a single common point - the header for the transformer secondary. You should not conflate the two.
The DMC wavy line issue is usually fixed by replacing the 150uF @ 160V capacitors. These are C28 and C42. These are standard 7.5mm lead spacing capacitors.
The sound AC rectification filter capacitors you probably changed are C36 and C37. These are standard 10mm lead spacing radial snap-in capacitors. Removing these can be problematic as it is easy to pull the plated through hole when you remove the capacitor. It often leaves a "brown donut" on the capacitor.
Quoted from BentleyBear:I have double checked my work multiple times and all looks good but when i turn the game on it makes this incredible loud noise so something must be wrong.
You should triple check your work by measuring continuity between the ground plane (reference) and the small ground area on the back side of the board. This small area is on the back of the board and is attached to the positive pad of C37. If you pull this plated through hole then everything connected to the ground area (and therefore the ground reference) is now "floating". The 79L05 is attached to this. The output of the 79L05 is therefore not correct and everything connected to the 79L05 output is now suspect. You probably blew U3 (the AD1851) in the process.
You may ask why I know this ...
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