EBD lamp sockets

I’ve always thought all controled lamps had diodes. Not sure but can you please document the hell out of this project because I’m in the same shoes. Have an 84 that I want to convert to a 81.

As far as I knew only Williams games need them because they have a lamp matrix, and bally/stern/gottlieb never needed them, so curious why this one does have them...

They won't seem to be shown in the schematics?

Okay, this one peaked my curiosity because I have never noticed it before. So after pouring over pics of my '84 EBD and a Black Pyramid I used to own(it used light boards too) I see NO lamp sockets with diodes. Weird. Maybe a test model?

Shawn

Chris, some of the '82 LE games had lamp boards, too. Not sure when in the run they made the change, but I have seen a couple of them come through my hands. I don't recall any diodes on the controlled lamps on either one of those '82 games. They may have been there, I just don't recall them.

As far as those lamps with the diodes, I believe they would all run through the auxiliary lamp board-A9 with the controlled GI, while the lamps that use the playfield lamp boards run through the lamp driver board-A5. Not sure what problem Bally would be trying to solve with those diodes, might have to think on that one a bit. That A9 board did have a lot of problems with burnt connectors and header pins. Also, those playfield lamp boards simply replace the sockets and have no other functionality, besides being really convenient. Real similar to KISS in that respect.

My '84 has those diodes, too. Maybe a mid-run change?

Diodes on the lamp sockets were used on Bally games that had dual phase feature lamps. They were rare in the Bally-35 architecture - Gold Ball was one game that had them. This became standard in the 6803 games. It was essentially a simple, cheap and clever way of being able to double the amount of feature lamps the platform could have.

I'd say your '84 EBD has leftover sockets intended for dual phase games. The only effect those diodes will have on your game is the lamps may be slightly dimmer since they have a voltage drop around 0.6 volts. The playfield lamp boards with the black twist socketed lamps don't have diodes right?

Since EBD is a single phase feature lamp game, those diodes on the lamp sockets are not needed.

I was gonna say the diodes are only needed in games with lamp matrices for isolation from the other lamps on the row or column. Bally used 1 SCR per Lamp so no isolation diode would be needed.