I've got a couple flashers out. Number 3 on the back panel is out but the paired number 3 on the playfield works, as does the #3 solenoid, so I believe I can rule out the driver board and assume this one to be a bulb/socket issue. Number 4 is out in both locations. Solenoid 4 is a spare so I can't test the electromagnetic device. Can I perform a typical "ground the transistor" test as I would to test a solenoid, stopping the test on Flasher 4 then briefly grounding the tab?

Thanks guys. I should have mentioned that the resistor board is a new one and I did put a new bulb in the #4 socket nearest the player but it remains dark.

Grounding the tab on Q24 does nothing. If I'm reading the schematic correctly I should have Solenoid B+ on the bulb all the time and the driver circuit just provides ground, so I ought to be able to meter for around 35V, right? Also, if I ground the socket tab directly, the bulb should light, verifying the bulb, socket and power.

Where do I go from there? The schematic doesn't seem to show these flashers very well. I gather from the table on the front cover there's a connection to the diode board. Is that a likely next step?

So no progress yet. I do seem to have voltage at the socket, which makes sense as the voltage feed is just a short jumper from the #5 socket. With that in mind, I started tracing wiring. I have good connectivity on the control wire down to the diode board at B4. I don't seem to be able to continuity check past the diode however. Measurement across the diode is the same as the other diodes on that board.

Any other thoughts on how to go about troubleshooting this?

So I tried a number of the troubleshooting steps in the other thread but everything looks good. I have continuity from the banded side of the diode to the Q24 tab. I have good connectivity from the playfield #4 socket to the unbanded side of the diode. The diode meters just like all the others. Q24 is new. Now, when I put it in Flasher 4 test and ground the Q24 tab to the GND test point on the MPU, I immediately start to get a noticeable hum. It sounds like if I held it there, something would blow.

I am now wondering if there isn't a short in the lamp on the back of the playfield. I'm think what I might do next is to split the 2 control wires at the playfield socket, find the one that connects to the resistor board and attach only that one.

Any other thoughts?

Here's the flasher 4 board:

IMG_0054 (resized).JPG

Here's the back side of another new one so you can see the traces.

IMG_0055 (resized).JPG

One thing I did differently was splitting the two ground wires to both sides as the holes were a little small. I can't see that this matters as the trace is fully connected across both.

Some new info...

I disconnected both white/yellow wires from the lower playfield #4 flasher. I identified which of the two went to the driver board and jumpered it to the socket. Put it in test mode and the flasher worked.

I metered the second white/yellow wire down to the molex at the bottom of the playfield where it goes back to the rear lamps. With the lead disconnected, no continuity between the lead and the orange voltage wire. With the lead jumpered to the socket, good continuity, so I think the main playfield wiring is good.

Metering the orange and white/yellow pins on the other side of the molex also shows continuity but now Ieed to try and get that darned bulb out of there to see it the continuity opens when it's removed.

My game is early enough that it does not have the PC board for those lamps. It's all point to point so pulling the playfield may be unavoidable.

Problem identified!

IMG_1864 (resized).JPG

Guess I'm ordering a socket

Many thanks also to whomever originally posted a comment somewhere about replacing lamps from the back of the cabinet through the vent grille. That worked like a champ for replacing the #3 bulb which now works great.

On a side note, anyone able to grab a photo of the cable clamping and routing behind the playfield, with it on the prop bar? I'm pretty sure mine is mis-routed and may have contributed to pulling that socket apart.