Classic Sterns and Bally need either an Alltek LED lamp board ($99) or a resistor soldered to each lamp socket in order to use LEDs in the playfield inserts.

http://www.bigdaddy-enterprises.com/boards/boards-index.htm#alltekmpu

Not every lamp will need a resistor either. I use the LED's from comet pinball and add resistors (470ohm) where needed. The ghost busters don't help on this era of game because of the way the lamp is driven by the board. GI is always fine in this era when using LEDs.

No problem using LEDs in the GI, just the controlled lamps.

You should not need rectified or "ghost free" bulbs for feature lamps since they are all individually driven by an SCR and not matrixed. Once the resistor is added (to keep the SCR turned on) they should light solid (to your eye).

Learn something new every day on pinside !

Yeah. The rectification happened already for the feature lamps on the transformer assembly. Only downfall is you would just have to make sure the bulb gets put in the right direction / wired the right direction. Shouldnt matter on bayonet as long as no one has monkeyed around with the sockets.

If you want to do LEDs in the GI, use rectified LEDs there or else they will flicker 60 times a second and bug my eyes. GI is AC, without rectification they will only be on half the time.

Have to assume the no flicker plus ones have a cap in there too smoothing things out even more?

Most common misconception on Pinside regarding LEDs = Flickering and Ghosting are the same.

Actually, they are NOT the same things AT ALL!

Folks will purchse the ghostbusting leds and then wonder why they flicker??? Because they don't eliminate flicker, they only eliminate ghosting (ghosting=lamps being slightly lit when they are not supposed to be lit).

Have you tried a No-Flix, or Optix Super Flux in this application?

That flicker is from the SCR on the lamp driver board being unable to latch because the LED does not draw enough current. The fix is to add a resistor to increase the load so the SCR stays latched. This can be added anywhere, just go between feature lamp bus and the ground wire of each lamp. 200-500 ohm is a good resistor choice.

No, the Alltek board latches fine with the low load of the LED.

The Alltek lamp driver board works great in classic Sterns and Ballys for reducing the flicker.

I always use them for powering LEDs in my classic Stern/Bally games.
http://www.allteksystems.com/

The alltek board has you hack, i mean alligator clip, to the feature lamp bus, so they can load each SCR with an on board resistor.

The alltek board does the same thing adding a resistor does. Alltek is just doing this on the lamp driver.

http://www.bigdaddy-enterprises.com/images/Alltek%20Lamp_Driver_Picture.JPG

See the instructions on the top left and the resistor networks by the output connector pins are what loads up the SCRs so they dont blink.

Yep, it works great in all my classic Bally and Sterns.

Highly recommended.

I have the Alltek lamp board in my Flash Gordon (and yes the aux lamp board too). This is in conjunction with an Alltek MPU. It still strobes some of the LEDs and has a highly flickery character overall. Not sure why. I'm considering adding the resistors as I've seen a different FG done with them and LEDs and it was rock steady, much more like the steadiness of incandescent (only much nicer colors). Maybe the Alltek isn't giving me quite enough current draw.

If you want to go LED, but not get the LED brightness issues, I highly suggest cointaker frosted LED's under inserts. The warm white frosted are extremely close in appearance to incandescent under an insert.

But to be honest, I see now they are advertising a 2-led style which is different from the ones I've used in the past. I don't know if this would change my opinion. If they are brighter, I may start making a different suggestion. When I tested the older ones with a lux meter, they had an identical reading to incandescent bulbs in a bayonet mount.

Did you run feature lamp voltage to the lamp board like instructions say printed on the top left of the board?