I'm in the process of converting my Bally Star Trek to all LED lighting.
I've done all the GI lights and will be fitting Yoppscile LEDs under the playfield, but behind the backglass for the controlled lights I want to use the baynet LEDs and solder 470 ohm resistors across the sockets.

I did a test on the double bulb 'High Score to Date' and 'Game over lights' and with a 470 ohm resistor fitted it reduces flicker, but doesn't make it completely go away, changing to a 220 ohm resistor was no better, so for now have removed the resistors and put back in the incandescent bulbs which when they light up are very dull.
I've repinned the connectors to the lights and on my rectifier board and replaced the old tarnished fuses with new fuses.
My lamp board is still the original Bally board and I can see some of the MCR106 SCRs have corrosion damage on them from a leaking battery in the past.

I have tried to test the SCRs using my diode tester on my meterand ever single SCR gave a similar reading which was well out of range for what Pinwiki tells me I should get. So either all my SCRs are failing or my meter is not right.

Would I be correct in assuming that the dull incandescent bulbs and flickering LEDs that can't be fixed by fitting a resistor is likely due to the SCR failing as long as I know all the rest of the wiring is good?
I'm just debating on weather to buy a stack of MCR106-6 and 2N5060 to replace on any light that the 470 ohm resistor doesn't fix the flickering issue or is there something else I should also be looking at?

Yes I could just buy a modern light board, but would rather keep the original board if I can.

Thanks for your help.

No only a 470 ohm and then a 220 ohm when the 470 ohm didn't get rid of the flicker.
I would of thought a higher ohm resistor would be worse as it would give even less current draw.
I've not tried cleaning the light sockets but all the GI lights are fine, I've only got really dull incandescent bulbs on the controlled ones on the backboard, other than 3 sockets under the playfield that were completely shot and didn't work at all, all the others have been fine.

Tomorrow I'm going to install a few of the Yoppsicle LEDs under the playfield and see if they work as intended or also give me flickering.
Just about everything else on this machine has needed some TLC and I've not given any to the light board yet so it is probably due some.

Thank you, you were spot on. Measured around 3vDC with my meter and when I dragged out my scope it gave a perfect example of half wave rectification, looks like time for some repair work on the rectifier board.

faulty bridge rectifier (resized).jpg