I'm troubleshooting an issue with a The Shadow I acquired a while back and have been working on. When firing either or both of the flippers, either via the buttons or in test mode, the game instantly resets. While this falls into the category of a WPC reset and is probably watchdog circuit-related, I'm not convinced that it's due to the typical culprits affecting the 5v or 12v supply. This is very much something that happens only when the flippers fire, and not seemingly randomly or otherwise. The game has sat on for about a half hour or more at a time in test and attract mode while I've been servicing it and I've yet to see a reset in either mode, unless/until the flippers fire.

I should also note that the flipper EOS switches (all of them) throw errors on boot. They are normally open in test and register properly when manually closed.

Things I've done so far (all measurements coming from my true RMS Fluke 8060a), using the Pinwiki WPC reset troubleshooting list (https://pinwiki.com/wiki/index.php?title=Williams_WPC#Game_resets) as a guide:
- Reseated all connectors, including J101, J114 and J210, many times
- Verified that line voltage is 122VAC and that matches what I'm getting with the game on and off at the internal supply
- Verified driver board (and all boards) are screwed in fully and grounded
- Flowed more solder to all of the flipper coil lugs, ensuring the diode leads are fully in contact
- Unplugged/plugged back in the 15-pin Molex at the transformer that carries 9VAC
- Checked pins at J101 and I don't see significant tarnish
- Measured VDC at TP2 and again at pin 32 of the game ROM and here I am seeing a bit of a drop - 4.925v at TP2 and 4.686v at pin32 of the ROM.

^-- Is this a clue of the root cause? Are these voltages too low on both sides? --^

- Tested BR2 on the Driver Board and while load using the method here (http://techniek.flipperwinkel.nl/wpc/index2.htm#reset) and got 9.6v. I also tested under load using this method (https://pinwiki.com/wiki/index.php?title=Williams_WPC#Using_a_Multimeter_to_Test_the_Bridge_Rectifier_and_Capacitors) and got 9.8-10.02v. Checking the capacitor I measured 183mVAC, which also seems to be a bit low but in range.
- Tested BR1 under load on the Fliptronics II board using method from flipperwinkel and got 67.5v-68.1v
- Went to test C2 on the Fliptronics board and HOLD UP - it's not there! It looks like it never was?! But I'm assuming this is factory normal on this game, from the pics I've seen.

Here are my thoughts on how I might troubleshoot further:
- Remove the flipper assemblies (which I just rebuilt and replaced ) and check all of the flipper diodes one by one by taking them momentarily out of circuit. They appear to be visibly wired properly, but I stupidly didn't test them when I had the assemblies out.

^--See attached photos. I verified wiring at the lugs matches the schematics and I believe the EOS switches can be wired either way and work fine. But please feel free to fact check me here.

- Check for a short on the flipper circuits. What's the best way to do this?
- Check thermistor: I don't think this would be the cause given how these resets are isolated only to the flippers engaging. But could it be?

Any additional suggestions or thoughts would be much appreciated. I've spent a number hours already on this and would love some guidance before I invest more time here. I'd like to be 100% sure this is a Power Driver or Fliptronics board issue and not something else before I engage a trusted professional here.

Many thanks in advance!

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No problem at all. I've seen that pattern before too and figured I'd save us all the headache.

I totally did. Reversing the outer lug wiring to properly match the schematics did the trick. Thanks!

Great callout. I was working on a Big Guns flipper issue recently and I think that I had burned into my brain the old mounting standard for coils. I didn't realize it changed in the 90's. I have a feeling this is why I flipped the wiring.

Now for a new issue. The hits just keep coming! The right flippers work great and no more EOS switch errors on boot. However, the left flipper won't fire at all, via the button nor via test mode. I'm going to start tracing the power from the driver board and see if I can figure out where things go sideways.

@dumbass, if you or anyone has suggestions on how to best troubleshoot this, I'm all ears.

Wow! Thank you both. This kind of support is exactly why I love the Pinside community. This reminded me to send in a donation to keep this great community rolling for years to come. Thanks again DumbAss and @ltg!

As for the troubleshooting, here's where we are:

The switch works fine in edge test.

Nope. 0VDC, whether firing or not.

F904 was blackened and failed testing when removed. I replaced it with a new 3A 250V SB. F112 and F902 look and tested fine.

Still no voltage when I powered it up, after replacing the bad fuse. Transistors Q3, Q9 and Q10 all failed the Pinwiki-prescribed test (https://www.pinwiki.com/wiki/index.php?title=General#Testing_a_Transistor.2C_Silicon_Controlled_Rectifier_.28SCR.29_or_Field_Effect_Transistor_.28FET.29). They gave clear readings of 0v compared to the .4-.6v ratings I was getting on the rest of the transistors.

I've replaced a couple of transistors and similar non-surface mounted components on other boards successfully, previously. While I don't have a top of the line Hakko desoldering gun, I do have a desoldering vacuum-pump and a vintage Weller WTCPT soldering station that I am quite comfortable with (it even has a brand new tip I just installed). How sensitive are the traces and through holes on the Fliptronics board around the transistors? Am I highly likely to cause damage if I don't have a nicer desoldering station?

Additionally, is it possible there might be damage further back from these transistors on the Fliptronics or Power Driver boards? I'm assuming no since the R flippers work. But please keep me honest here.

Nope. This is not what I'm seeing. The solenoid never fires at all. Since I've replaced the fuse, I'm still not seeing any power at the solenoid.

So I'm getting about 32 VAC coming in at J901, on each pin. I expected 50 VAC or more. Is this indicative of an issue?

J907 is giving readings of about 61-62VDC on all pins except 5-6, which are reading 0.56 VDC. Ah-ha! I think? But shouldn't this have affected both the lower left and lower right flippers?

Just for grins, I also tested continuity along Red-Blue from the solenoid supply lug to J907 (pins 4-5) and it tested fine. So we shouldn't have a wiring issue there.

Given the above, what should I test next?

I'm getting a fluxing but consistent ~55.4VAC across every one of these pairs.

Across each pair, when tested with fuses isolated, I'm getting ~62.4-63VDC. Again, there's some flux but the range is consistent. As a side note, I decided to test each fuse when I pulled it and did find that one of them was toast. I replaced it and reseated the rest, then fired up the game hoping for a miracle. Sadly, that left flipper remains unresponsive. And not surprisingly, I'm still measuring 0VDC at the supply side lug on the solenoid.

Where should we go from here?

Bumpity bump. Anyone? Bueller? Bueller?

I'm at a loss here for where to go next.

Right. So I confirmed continuity to all 3 of the wires going to the solenoid from J902 and J907.
For grins, I tested voltage again at J907. 1-2, 6-7 read ~67VDC. But now I'm getting 0VDC at 4-5 (Red-Blue). I confirmed this a 2nd time. I checked F904 out of circuit and its good. It looks we might have found something here.

I'm assuming we're going to be chasing the lack of voltage at 4-5 now, but here are some photos of the wiring at the L flipper solenoid now, just so we can fully rule that out.

I did notice this and it threw me off originally, but since it looked like this was factory original, I didn't sweat it. Good to know, though.

IMG_20200923_232548 (resized).jpg

IMG_20200923_232603 (resized).jpg

Wow, thanks for making this easy for us, Williams. Sheesh. Anyway, I removed all fuses including F902, verified they were all good and replaced F902 alone. I'm still getting 0VDC at J907-4,5. Interestingly, the fuse blew sometime while I was taking voltage measures. Not sure if I accidentally caused a short while I was probing or if this is just related to our issue. But I figured I'd call it out, just the same.

Here's are shots of the front and back. I don't see any evidence of prior board work, nor do I see any cold solder joints. But my eyes certainly could be missing something.

IMG_20200924_230040 (resized).jpgIMG_20200924_230052 (resized).jpg

All continuity on these checks fine. I should note that you said RED-GRN but I'm pretty sure you meant RED-BLU, which is for our problem flipper. But I went ahead and checked continuity on RED-GRN too, just to be thorough. It was good too.

I'm definitely getting lower than nominal voltage at all of these points: 65.4-66.8VDC. It goes up just a bit the longer I leave it on, hence the range.

Yep. It lit up like a Christmas tree the moment I turned it on. Time to buy a few more 3A MDLs. I only have 4 left now, just enough for the 4 on the Fliptronics board - no more spares.

What's next?

Tested all 3 using the Pinwiki-prescribed testing procedures. I had done this a while back and all 3 tested bad, but it can't hurt to try it again.
Q3 does not short on its center leg, so it tested bad.
Q9's left leg tests out of spec, so it is bad.
Q10 tests fine, but I wonder if it might be bad too. If I'm replacing Q9, I'm thinking I'll just replace Q10 while I'm at it unless you think otherwise.

I got 0.14ohm on both of these. Definitely no bueno. I tested the other flipper coils just to make sure it wasn't user error with my DMM and they tested fine.

Yep. Both are shorted.

I'm placing an order with PL here tonight for the diodes and transistors. I need a lamp bulb for one of the rings while I'm at it.

I'll report back after doing the requisite board and coil assembly work. Probably will be a few days.

After replacing Q3, Q9 and Q10 on the Fliptronics board, as well as the 1N4004 diodes on the flipper coil, I'm happy to report that the left flipper is working again! Huzzah!

HUGE thanks to DumbAss for his diligence and patience, without which, I'm sure I would still be spinning on this one.

I hope that this thread lives on to serve the community as well as it did me.