Have you tried running the coil test to see if it fires in test mode?

After running test mode and observing the action, if there’s a difference, check your contact gaps to make sure you’re getting a good wiping action when they make. You might just barely be making the switch.

Was the bumper working before, or was it in this condition when you got it?

Could you take a few pics of the pop bumper underneath the playfield? It may help if we can see how the wiring for the coil and switch is configured etc.

is the leaf switch in the right stationary position ?

Look at the switch. Is there a gap in it? Looks like it is closed when it should have a gap.

Just curious, what was wrong with the previous mpu board?

What voltage are your measuring at the coil?

Here's a couple things that may help, including a procedure for firing the coil with an alligator test clip:

Testing for Power at a Coil/Flashlamp.
If the coil does not fire, there may be no power at that coil or flashlamp. For this test, solenoid fuse F2 will need to be installed. Using a DMM set to DC volts, do the following:

Lift the playfield up on the game.
Turn the game on and let it go into attract mode.
Put the DMM black lead on ground (the metal side rail).
Put the DMM red lead on EITHER coil lug or flashlamp lug.
Either lug should show 28 volts (for either a coil or flashlamp, as flashlamp power is the same 28 volt power source).
If only one lug shows voltage, the coil or flashlamp is bad (it has a broken winding). If neither lug shows voltage, check "upstream" and see if the daisy-chained thicker power wire broke off another coil/flashlamp in the chain.

Testing the Coil/flashlamp.
If a coil or flashlamp is not firing, and with power at the coil, this test will check if the coil or flashlamp is capable of firing. For this test, solenoid fuse F2 will need to be installed.

Lift the playfield up on the game.
Turn the game on and let it go into attract mode.
Using an alligator test lead, attach one end to ground (the game's metal side rail).
Momentarily touch the other end of the alligator test lead to the GROUND coil or flashlamp lug. The ground coil lug is the lug with the non-banded side of the 1N4004 diode attached (all coils should have a 1N4004 diode!), and the thinner wire attached. The ground lug on a flashlamp is the lug that goes to the resistors (usually the tip of the flashlamp socket).

I hope you kept the original board. I would use this to practice soldering and replace the chip and transistors that are bad. I am not the best tech, but am learning by fixing my own stuff. Keep this thread bumped and someone who is more knowledgeable than will help you. Especially if you are willing to tinker and learn. In the long run you will probably need a soldering pencil and a logic probe. The parts are cheap if you just practice and learn how to replace them.

I'm wondering if this is where the trouble started. I presume the bumper had been working before he started messing with it? Do all the rest of the coils fire in coil test except the one pop bumper?

I'm not really familiar with rottendog boards, but my next suggestion would be to ground the metal tab of the transistor that fires that coil from the driver board. If I'm looking at the schematic correctly, i believe it's the metal tab on Q4 you want to *briefly* ground. If you do that, does the coil fire?

Did the rottendog board come with schematics by any chance?

http://arcadeshop.com.whsites.net/rottendog/mpu327/MPU327_schematic.pdf

I am certainly no expert, but I was told to test that with tip102 / tip120 but not on a tip36c. Are you sure these are ones that you can do this to without causing damage?

Well, it *seems* like the board is ok, i don't know how to troubleshoot that board any further unfortunately though...but a couple people did point out earlier that the pop bumper activation switch looks like it may be suspect. Can you post more pics of the switch? I'd like to see the contacts better, and the wiring to that switch if possible.

If you open the playfield, you can watch what the switch is doing under the playfield while you push the pop bumper skirt by hand. Are the contacts on the switch leaves stuck pushed together? Are they gapped too far apart that they don't make contact at all? They should have a small gap between them (approx 1/16" but adjust as needed). Once you've verified the switch is gapped properly, clean the contacts on the switch as well. I use rubbing alcohol on a qtip, then pinch a clean piece of paper between the contacts and pull it through a couple times to remove any crud. Just don't file these types of switches! I've attached a pic with an arrow pointing the switch I'm talking about.
153676571.png

^ I believe the switch is a false path, as he stated earlier that the Pop coil doesn't work in test mode. The switch wouldn't prevent this.

What I've gleaned so far, if the OP is accurate in his description: The Pop works when the transistor is grounded (Q4), but does not work in game or test mode. If all that's true, it would seem to me its the pre-driver circuit or logic ahead of Q4. That's not to say the switch isn't shorted and caused the pop to lock on and damaged the board at some point, but it doesn't seem the switch right now is preventing the coil from working.

OP, do you have a logic probe? If so, compare the operation of Q2 vs Q4 (don't know what coil is on Q2, but you should).

Go into test mode, put your logic probe on R109 ahead of Q2, and run the test for the coil on Q2 and note the signal change. Then do the same on R112 which is ahead of Q4 and see if the signal behaves the same. If not, board issue.

Totally agree, i think I'm just hesitant to diagnose it as a bad board since it's apparently a brand new one (and i don't know enough about rottendog boards to suggest any further board troubleshooting)...figured if we know 100% the switch is ok, then I'd circle back to the board being bad. Still, diagnostically everything he's done so far does point to a board problem regardless of the switch--it's not firing in test mode even though the coil has good voltage and wiring up to the transistor.

Honestly, i was kinda hoping someone with a bit more knowledge might jump in and steer us in the right direction, so thank you!

Was it new? The sticker on the Driver board looks like Sept 2015 (but it's cut off). Wasn't sure if it was a new board, or a spare RD laying around. And, it could have been a locked on coil that damaged it. Who knows, but a quick test with a logic probe can confirm it.

Yeah, that's a good question. I didn't even think to look for a date! I assumed it was new, but OP did say they gave him a good deal on the board so maybe it was a used one?

Yes, that will work. + (red) goes to any 5VDC source, - (black) goes to ground (usually ground strap is easiest). Not familiar enough with the Rottendog board to know, but usually there is a test point on boards marked 5V (it'll be a gray metal post). If you can't find that, looking at the schematics, you can clip it to the NON-banded side of Diode D17 which is up near the Battery Holder.

Edit: I see on the schematic, a TP9 (test point 9), so if you can find that, clip it to that. Should be near IC20.

Just clip to D7 as I suggested. To verify, put your meter on VDC, black lead in ground strap, red lead on non banded side of D7. If it measures apx 5VDC you can use it or probably any other location that you see VCC printed on the board. Any convenient spot you can measure a constsnt 5vdc.

Yes, make sure the probe is set to TTL. Touch the probe to the VCC test pad then the ground test pad. You should see the probe indicate hi on VCC and lo on ground.

The IRQ test pad should be pulsing hi and lo.

Couple of things...make sure the switch is on TTL. You can then touch the probe to the same point you clipped the red lead to, and you should read a high signal. Touch it to gnd or where you clipped the black lead and you should read low on the probe. Also verify with your meter that in test mode you are reading 5vdc between the red and black leads of your probe. Maybe you clipped it to a 5v source that goes away in test so the probe isnt powered up.

Lol....what he said....hes a faster typer.

Great minds think alike!

Check the schematics. If the pulse is not present, follow the path upstream until you find it. See if it comes into the chip associated with that coil. If so, is it coming out?

Not likely that R112 is suspect, but you can check it two ways. Put your meter on OHMs and measure across it. Compare it to the others, but should be 10Kohm. Or, using your logic probe, check both sides and see if you see the low pulse during test mode. If you see it on one side but not the other, then the resistor is burnt open.

However, unfortunately, it is more likely that IC9 is damaged. IC9 is a 74HCT240N chip. R112 is Q1 or pin 5 on the chip. R109 by comparison is Q0 or pin 3 on the chip. You can see the pin #'s here: https://assets.nexperia.com/documents/data-sheet/74HC_HCT240.pdf (Figure 5). The schematic from RD uses D0/Q0 nomenclature, and the IC datasheet uses A/Y, but just ignore those and concentrate on the pin #'s. You can test pins 3,5,7,9,18,16 which correspond to R109/Q2, R112/Q4, R165/Q6, R118/Q8, R161/Q10 and R124/Q12.

So, basically do the test you just did, but use your probe one step back on the IC pins instead of the resistors.

The notch is always the top....corresponds to the circle in figure 4.

I reread your first test...you may have already did what I was asking about checking both sides of r112...are you saying you get a pulse on one side of r112 but not the other? If so, then r112 is bad. Check it with an ohm meter with power off. Compare it to the others.

Replace it.