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Playboy by Bally 1978


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Had a weird problem with Playboy Playboy 1978 by Bally-i.jpg

 

Basically the machine would not fire up after playing it a few hours before, not mine so I felt a bit bad, after a few checks noticed that the power supply was not giving the correct voltages it was only out .5 to .8 volt D.C so the MPU wasn't firing up. Cut a long story short it turned out that the common ground points were not interlinked between boards, was only getting partial readings then no readings then some readings so it was weird, anyway temporarily placed a common point and wamabalama it fired up, why these were not fitted initially I will never know, anyway might help someone else.

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No everything was in tack as it should be, with the check points at the power supply it pointed to a bridge rectifier, so I thought, I believe that the common ground was floating causing a ripple effect instead of allowing true D.C. , the fix was easy, just used a jumper lead for now, what else could it have been? Do you have any suggestions :D
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I'm only guessing but in between all that messing around you may have fixed one problem but bought to light the most common problem with these old girls which is the Rectifier board mounted above the transformer in the headbox. The original boards are waaaaaay past the use by date.
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Read somewhere of failure of the metal backplane and the later Bally foil type soft cardboard backplane and a simple 'daisy chain' connecting the all the grounds is a reliable and easy fix.
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