While playing my Frontier pin, all of the coils except the flippers and knocker suddenly stopped working.  Under playfield fuse tests okay, as do all the rectifier fuses and HV fuse.  I checked for 43 volts at all the places instructed in Marvin's guide, and everything ckecks out okay.  According to that document, the only thing left appears to be a failed bridge rectifier.  Is there possibly something else I might check or try ?  

If it is pertinent, I have noticed the last couple of days that the sound will cut out udring ball play and then come back on for the next ball.

If you're certain that the playfield fuse is okay, reseat all of the connectors on the driver board and see what happens.

I reseated the connectors on the driver board.  Everything started working for the first ball or two, then the drop target reset coil on the right side failed to reset on the third ball.  Then the slingshots stopped working, even though everything else was okay.  Fourth ball, everything was fine again, then on last ball, no target resets and no slings.  This is a new thing.  Before it was all coils or nothing....now it seems the target reset and sling coils work intermittently.

Any cold solder joints under the header pins of J4 on the MPU ?
Or bad pins in that J4 connector housing ?

Otherwise the problem is with cold solder joints/corrosion on pins
of the solenoid driver board.

Cheers,
- Sylvain.

I appreciate the suggestions. I'm going to look more closely for cold solder joints tomorrow.  The MPU is a new Alteck, so I guess I'll start with the J4 housing and then the driver board pins.  

Thanks