I'd start by pulling all the LED's out in those sockets and replace with #47 lamps.

Feature lamps all share the same power source from the braid under the PF. Each is grounded thru the lamp board as directed by the MPU.

Start with one replacement bulb, put in a 47.

I'll lift the PF on my FG and check the braid layout. The GI lighting braid if crossed to the feature light braid could also cause that problem.

Mini bonus ring braid is to all the lights in that circle. What happens on a lamp test? (1st push of the test button inside coin door).

So in lamp test the only feature lights that flash are in the mini bonus ring? No other feature lights are flashing? When 1st powered on and in attract mode, the only feature lights that cycle are the ones in the mini bonus circle?

I'd replace all the suspect LED's and stick in #47's. Had a similar issue on my Xenon. I's assume the one #47 is behaving properly in test mode?

Alltek and Weebly make replacement lamp boards (yours also has the aux board) that support LED's when wired into the feature lights. I put the Allek in my Xenon without the Aux board and had the flicker issue. I'm not an expert but I assume with LED's you'd need to replace both and wire into the feature lights. If you replace all the LED's with 47's and the problem is gone, that's the issue.

These old Ballys were never designed with LED lighting in mind and there are some inherent problems with it.

Replacing the lamp driver board as tomdrum mentioned with modern lamp driver boards is one solution, other solutions are:

Using Siegecrafts LED anti-flicker adapters:
http://www.siegecraft.us/presta/index.php?id_product=44&controller=product

Soldering a 470 ohm resistor across each of those lamp sockets at the problematic locations.

Just revert to using incandescent lamps at those problematic lamp locations.

If it's just those sockets I'd do the individual resistors and save some money

I've looked at those but they haven't been available for awhile. I'd give that a try myself when available again.

Did you replace all the suspect LED's and the problem is gone? 1st step. Quench is an expert unlike me.

The feature lamps on these games are pulsed (switched on and off) at a rate of about 120 times per second when they need to be illuminated. This rate is too fast for your eyes to perceive so they appear to just be on, coupled with the fact that incandescent lamps these were originally designed for have long light persistence compared to LEDs that have no persistence.

The LEDs in the mini bonus area are flickering because they're the very first lot of lamps that are "refreshed" during the lamp activation service. During this time, LEDs cannot draw enough current to keep the lamp driver board switching circuits on, resulting in those LEDs switching off too quickly.

All the solutions I mentioned above in post #13 essentially put more load on the lamp driver board switching circuits so the switching circuits are able to function as intended.

Need to know which lamp you're referring to.

"4 Drop Target A (bottom)" lamp wire goes to J1 pin 24.

Grab a piece of jumper wire with both ends stripped and connect one end to ground somewhere in the cabinet.
Touch (i.e. ground) the other end of the wire on the lamp socket as indicated in the picture below. If the lamp doesn't light, that will tell you the problem is local to the lamp/socket.

On a real Bally lamp driver board, SCR Q1 drives that lamp. I don't know which SCR it is on the Alltek since they don't publish schematics but let's presume it's also Q1.
With your jumper wire still connected to ground somewhere, touch the other end of the wire on the metal tab part on top of Q1 on the lamp driver board. If that lamp illuminates, it tells you wiring from the lamp driver board to the lamp is good (note this doesn't test the SCR itself).
If it doesn't illuminate, there's a connection issue between the SCR and the lamp, check the connector at J1 pin 4 on the lamp driver board.

If the lamp illuminated when grounding the metal tab of the Q1 SCR in the previous test, then next need to test the SCR itself.
Disconnect your ground wire and then hold one end of the wire on the TP3 test point metal tab on the lamp driver board. Touch the other end of the wire on the lower left pin of Q1. If the lamp lights, the Q1 SCR is ok and it's the U1 controller chip on the lamp board that's suspect. If it doesn't light then suspect the Q1 SCR.

Lamp_Socket_Controlled.jpg

The lower left pin of Q1 marked "G" is the SCRs "Gate" pin. Actually the leg comes directly out of the black plastic package. The dots you see let you solder in standard SCRs that are not the surface mount type.

The purpose of test point TP3 is to allow you to manually activate the SCRs to test if they are working. If you connect TP3 to the Gate leg of any SCR, the respective lamp that SCR controls should illuminate.
For example if you connect TP3 to the Gate leg of Q2, the right side lower target lamp should illuminate.
Connecting TP3 to the Gate of Q3 should illuminate the "Shoot Again" lamp behind the backglass.
Test these two SCRs (Q2 and Q3) with TP3 to see if the respective lamps illuminate so you get familiar with the process.

If hooking up TP3 to the Gate of Q1 does not illuminate the lamp, but hooking up ground to the upper metal tab of Q1 does illuminate the lamp, it says Q1 is suspect faulty.

Essentially the larger SCRs can handle more current so gave Bally the option to handle multiple lamps if needed. The smaller SCRs only drive one lamp. Yes the lamp driver boards are generic so while your game doesn't have many multiple lamp scenarios, other games may, so in your game most of the larger SCRs are just driving single lamps.