Im finishing up a Bally Mr and Mrs Pacman, but im having a problem with the lamps flickering(I have all comet LEDs installed). When I say lamps I mean ALL the lamps! GI, insert, and even the 555's that are under the pf for the solenoid expander and aux driver boards(which are not LED). Its a light but noticeable flicker.

Heres what I have done:

Bought Siegecraft LED adapters and tried an Alltek lamp driver board, no change.

Tried Alltek and Weebly MPU, no change.

IF you bypass the triac mounted on the power supply, the lights do not flicker. Also tried shorting it to 5v as recommended by someone which means the triac is good(I hear they never go bad).

The aux driver board 555 lamp does light, the solenoid expander 555 lamp will flash on and off with the other lamps in lamp test mode.

Not sure where to go from here. Need advice, thank you.

#2 4 years ago

HAN

HHaase

Siegecraft

14y 89,550 3,100 5 12

How fast are they flickering?
First thought I'm having is a rectifier that's partially failed.

As an oddball suggestion, just to rule things out, can you try a different wall socket that's on a different circuit?
Sometimes in old houses there's odd things going on with the 110v lines.

-Hans

#3 4 years ago

ZIT

Zitt

Pinball-Mods.com

Austin, TX

11y 112K 7,873 15 10

Quoted from HHaase:
How fast are they flickering?
First thought I'm having is a rectifier that's partially failed.

Exactly what I was thinking.
I'd check for an open on the bridge rectifier which is causing half of the wave to be missing. You shouldn't be able to see FWB rectified 60Hz at 120Hz. But you'd defiantly see half-wave rectified 60Hz on an LED and maybe even in the brightness of a incandescent.

#4 4 years ago

AMS

barakandl

nvram.weebly.com

12y 132K 10,417

I saw on facebook that increasing the display interrupt speed by adjusting the trim pot of on the NVRW replacement MPU fixed your flickering of lamps connected to the GI blinking triac board. That is pretty odd as I would expect slowing the display interrupt down if anything would help. I guess the display interrupt at certain frequencies makes the timing of the interrupt happen at a bad spot.

At some point, not sure exactly when, Bally changed the display interrupt speed to about 420hz from 320hz. Presumably to reduce display flickering when seven digit displays and extra displays are used. The final -35 using game schematics show MPU R21 changing to 24K from 36K. The replacement NVRW MPU has a trim pot which will adjust to about 320hz to 420hz. I normally leave the trim pot in the middle which works out to be around 360-380hz

#5 4 years ago

SPD

daly124

Pinside+ Frequent

Brick, NJ

7y 57,800 310 13

Yes I posted this shortly before I tried the trim pot adjustment which does fix the problem. Thanks again.

#6 4 years ago

BIL

dothedoo

Pinside member

12y 106K 7,265

What is NVRW?

#7 4 years ago

237

slochar

Pinside member

7y 86,550 6,903

NVram Weebly board I'd assume. Andrew's excellent replacement MPU board.

Of which I didn't even notice the pot on it until I'd installed 2-3 of them in my games.....

1 week later

#8 4 years ago

DAD

crazi

Pinside member

Coatbridge

15y 41,400 307 8 6

One to remember

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