It seems that every time I fix a problem in my HH, another one manifests. In today's episode, the pop bumper just above the upper left flipper on the main playfield has stopped working. I pulled the PBDB that drives it, 4A8, and removed the Lamda transistor from the circuit, thinking that was the culprit. Alas, it tests fine on my multimeter.

I checked continuity from the coil lead to the pin on connector 4A8J1 and that's fine, too.

All of the other pop bumpers are working.

What should I look for next?

Brilliant! Thx for the tip. I'll give that a try and see what happens.

Thanks, but nope. F11 tested fine with my meter.

Didn't check that yet. I'll do so as soon as I can get back in front of the game. Hopefully, later this afternoon.

Got a break from the holiday hoopla and did some more testing. Swapping boards 4A8 and 1A8 still left the pop bumper not working, while the bumper at 1A8 continued to work fine. So it's not the PBDB.

Then I noticed that the plastic supporting one of the leads of the coil had broken, so the whole terminal was floating free and looked like a short waiting to happen. So I painstakingly removed and replaced the coil with a new A-1496, per the manual. Powering it up, it still doesn't work.

Any ideas on what I should try next?

Tested voltage at both sides of the coils at 4A8, 1A8, 2A8:
1A8 (on main playfield): 37.2vdc
4A8 (also on main playfield, the non-working pop bumper): 0.7vdc
2A8 (upper playfield): 25.8vdc

I also tested voltage on both sides of fuses F10 and F11, just in case it was useful. They were both at 30vdc consistently.

So does this seem like a connection issue at PBDB 4A8?

Yep. I bought the game with all of them done except the aux. lamp driver, which I did myself. The MPU is a Ni-Wumpf, so I assume it doesn't need the grounding mod, correct?

I did try the swap, yes. The problem stayed with the pop bumper in question.

Got it. Let me do some testing with the transistor. Thanks for the direction!

Well, it looks like fuse F4 blew, which drives the solonoids. Coincidence? I wonder. I'm out of 8A Slo-Blo's, so this is on hold until my order comes in with more of them.

New fuse in place at F4, and we're back in business. Hot damn, Marco shipped fast, even with the holiday!

I'm getting 0.7VDC on the transistor case at 4A8, 25-34VDC on the three other transistors, in game.

I tried this and the pop still didn't fire.

Hmm - so since switch #44 controls both pop bumpers on the main playfield, wouldn't they both be affected if there was an issue with it? Happy to dig into it, though. What would I check at the switch with my meter?

Since the issue doesn't travel with the board, could it still be an issue with a bad cap?

Ok, good to know. Thanks! So there are four caps on the PBDB: C1-C4. I've placed an order for a handful of each type, which should hopefully be coming later this week. Anyone have ideas which one I should start with? If I had to guess, I'd say its C3, since it is the only one that actually is in circuit with one of the IC's (Z1), at least that's how I'm reading this schematic.

Makes sense. I see the two switches now. So the switch I want to check is the one that is triggered when the pop bumper skirt is hit (it sits above the other, scoring switch). Is that right?

I replaced the fuse and then I replaced the 4.7 mfd cap at C3 on the PBDB driving the pop that's not popping. I even made sure to connect the cap with the polarity reversed, as noted in the service bulletin that jmountjoy111 so kindly brought my attention to. Alas, the pop still ain't popping. Checking voltage at pin 5 on 4A8J1 gives me 5.01V, so that's good. I'm also getting ~34V on the lug of the offending pop's coil. That seems good too, yes? Just for grins, I manually triggered the scoring switch just below it, and it fires just fine.

So I have a friend who really thinks its the connector. Anyone here agree? If so, I need to get the right tool to remove the wires and reseat them in the connector terminal.

Any thoughts or suggestions here would be greatly appreciated. Thanks in advance!

I'm getting 37.5v on both lugs of the coil for the pop in question. That's the same reading that I get on the lugs of one of the working pops.

That makes sense and thanks for the tip. Alas, when I manually fire the switch for the pop, it still doesn't fire. I'm starting to think it could be the switch. How would I test that?

I carefully shorted the switch and it still didn't fire. I'm going to try and check the wiring to the switch. Continuity tests along the wires should help me get this sorted.