Q*Bert PLEASE HELP ME *************

[koolmoecraig]

Hello,

After I just replaced the amp chip, I realized that the 30V DC Led on the power board isn't even on.

Would this be a power supply probem or something less sinister?

Thanks all!
Craig
Velvetdoors1@yahoo.com

[OSCAR]

First check the 30VDC output with a voltage meter, sometimes those LED's will burn out, don't trust them.  Next verify that you are getting the 35VAC input from the transformer on the P2 header pins 3/4 & 9/10.  If you aren't getting the AC input to the rectifier board, then check the fuses on the transformer block.

If the AC input checks out okay, next check the F21 fuse on the power board, it is a 2A fuse.  If the fuse is okay and you still don't have power, then you probably want to check the D21-24 rectifier diodes.  From there, just start following the circuit on the board for any obviously burned/failed components.  Resoldering the header connections are also a good idea with the Gottlieb power supplies to help fix problems.

All else fails, you can ditch the Gottlieb power supply and replace it with a switcher.  This will require a little bit of rewiring, but it is possible.  I've heard some people using a lower voltage audio amp, like an LM380, so you only need 12VDC instead of the 30VDC required by the original LM379.

More info at http://www.ionpool.net/arcade/gottlieb/technical/switching_power.html & http://www.ionpool.net/arcade/gottlieb/technical/power.html.

[OSCAR]

I guess I should also mention to check the volume pot and the wiring between the power board, sound board, and speaker.  On my Centipede I recently restored, the sound just quit on me out of the blue.  It was working fine one moment, then the next time I powered it up, nada.  Turned out the volume pot was shot.  I replaced the pot and then it was working perfectly again.