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Museum of the Game® & International Arcade Museum® Forums
Working on a Wells Gardner 13K4713 from my Defender cocktail and having a issue with the B+ voltage not holding steady.
Quick history on this one, machine has had a issue since I picked it up with the monitor going into shutdown when cold. If you cycled power 4 or 5 times monitor would finally kick in and B+ would hold at 125.
I recapped and reflowed everything on the chassis and when watching power up the B+ would still go into shutdown when unit was cold. Once monitor came on machine would run no problem for hours and screen looks great.
I removed the glue from the B+ pot and turned it down just a bit and monitor now fires up and every time but was running at a slightly low 123 to 125V on B+.
Here is the weird bit , voltage is now moving up and down in a cycle about 1.5 volts ... takes about 4 seconds to swing up and another 4 to swing down, I am guessing this is not normal??
Base voltage to ground on the large VR regulator is also moving at same rate (TR502)
Case (collector) voltage is steady at 160V
I substituted resistors for the VR501 pot just to rule it out and problem did not change.
Newbie here and first time working on a monitor so thanks in advance for any help.