I picked up a working Gottlieb Mushroom World pinball recently and everything was working on it when I got it. Things worked fine for a bit when I was playing it at home and then I noticed the bottom pop bumper didn't appear to be doing anything. I checked the fuse and noticed that it was blown. I then checked around the pop bumper for any visible issues and found nothing... I replaced the fuse, it fired off and then blew the fuse again. So that's problem number one. I replaced the coil on it and I'm still getting an oddly low ohms reading... The other two pop bumpers get around 15-18 ohms, while the new one gets 2. The coil is the same part number as the other two and it's brand new. So I'm assuming short somewhere? How do I track it down?

Second problem: The right flipper died. The contact at the button still works as I can press the right button to cycle diagnostics... But other than that, it's not firing the coil. I checked the fuse and it's fine.

The thing is, both of these parts were replacements on the game and most everything else is original. So that leads me to believe it was a bad install job but I still really can't pinpoint where the problems are. I have since ordered new original Gottlieb flipper kits and I'm planning to install those tomorrow.

But generally I'm just wondering how exactly I can diagnose and track down the source of these fuses blowing. I've googled various guides and stuff but it's all very general and not specific to exactly the problem I'm having. Any help would be greatly appreciated. Thanks!

Awesome information! Thanks everyone!

Well I pulled out my A3 driver board and tested the Mosfets... Q3 looks to be the culprit. It's giving me a reading of 0.048 instead of 0.48 range like the others.

As for the flipper... The contacts seem to be okay... so I'm not sure what to do next. I plan to replace them both so maybe that will fix the issue outright.

He's a couple hours drive from me so it's unlikely he'd be able to just drive up and help me fix it... It stopped working a couple of days after I bought it so I mean I'm honestly not holding it against the seller because he let me test it and it was working fine. It just had a few replacement parts that I guess were questionable. He said I was free to text him if I had any issues but I would really like to just try to get it working myself and not bother the guy.

So... oddly enough, I went to rebuild the flippers and started disassembling the left flipper... only to realize I was missing the proper sized mounting plate so I had to reassemble it and wait for the part to arrive. I had taken the A3 board out to test the mosfets, but I put it back in just to try and diagnose the right flipper not working... After plugging everything back in and firing the game on, both flippers work just fine.

So I'm scratching my head as to what the problem might actually be... Is it possible that it was just a loose connection on the A3 board, and that detaching and reattaching the cables fixed it?

Right now I'm just waiting on the mosfet to arrive so I can swap the busted one out and hopefully that fixes my bumper issue.

I forgot that there's also 2 lights out on the back box display... but I'll look into that in a bit. It's possible something went bad on the light board, I'm assuming. I swapped the bulbs out with new ones and the smaller bulb isn't lighting still, but the larger bulb is getting a really dim light (the filament inside is just getting hot but not really lighting up bright) Does that sound like a board component issue?

Alright a little update... still not working so any help is greatly appreciated!

1. I tested the coil lugs and was not getting the 16 range reading the other two pop bumper coils were getting.

2. I removed the coil and desoldered one of the diode legs... The diode was giving me a bad number so I thought okay, maybe the diode is bad

3. I replaced the diode with a new one. I used an 1N4007 diode in place of what was there... I think it said 1N4006. I tested the lugs after that and was getting a good 16 range reading! Awesome.

4. I hooked it all back up and turned the game on. The fuse didn't immediately blow. I went into test mode. It got to the light test mode and I watched as the fuse heated up to red hot and then burned out. Okay...

5. At this point I'm thinking let me just check to see if this fuse is even the right one. I put in 1.5A but maybe it's wrong somehow? So I swapped the burned out fuse with a known working 1.5A fuse that was in the top pop bumper. So here's where the fun began... I'm running test mode again and watching that fuse like a hawk. It's not glowing anymore... didn't burn out... I'm like okay what is going on. Then I glance over at the coil and see it starting to smoke. I immediately power the game off. The coil is really hot to the touch but doesn't appear to be burned... I test the coil lugs and I'm getting 20ohms. The fuse is fine.

6. I let the coil cool down a bit and test it again. Getting 16ohms again. So I guess that's good... didn't screw the coil completely. I swapped the fuses back and now this is where I'm at.

On a side note, the mosfet I installed at Q3 is now giving me a wrong reading again. At this point it feels like a chicken/egg scenario... Is the bad mosfet causing the coil to burn/fuse to blow, or is the shorted coil causing the mosfet to crap out? I honestly don't know.

So any help would be greatly GREATLY appreciated. I don't want to do damage to anything at this point... Does any of this info pinpoint the problem? I can't find *anything* shorting the pop bumper out at all, and it's driving me nuts. Right now the coil is giving me a proper reading but it's blowing the fuses I'm putting in. When I swapped in one of the fuses from the other bumper, it didn't blow it, instead it started burning the coil... so I'm assuming the coil is getting too much voltage or it's shorted or something? I dunno. Help!

Update: I just read somewhere about how if the diode is bad it can fry the mosfet and if the mosfet is bad then it can fry the diode... So I thought maybe that was my issue... I checked the coil and it was good. Mosfet was bad. I replaced the mosfet with the last one I had on hand... tested good in the board. Coil still tested good hooked up...

Powered the game on... No burnt fuse. Tested the bumper... Nothing. Didn't burn the fuse. Coil didn't heat up. Mosfet didn't burn up. Coil still reads normal... But it's just doing nothing.

Anyone experience this? Do I check if it's getting power? Where is a safe place to ground the multimeter? I assume I set to DC, ground the black probe and then put the red probe on a coil lug? What reading should I get?

Thanks for the info.

Well I was playing the game yesterday with the bottom pop bumper just not functioning... As I played I noticed something.... The bumper fired. I had to double take because it happened so fast. I paid closer attention to it throughout the game and it totally seemed to be firing sometimes but not always.

I removed the playfield glass and just forced the bumpers to fire... It wasn't working. I kept trying and eventually it fired! Then it would fire maybe 7-8 times in a row, and then not at all. Then it would fire 1-2 times and not at all... It seems rather random as to when it decides it wants to work. What could be the culprit? I would think a loose wire but if it was anywhere near the bumper it would have probably just jarred completely loose at this point. On a possibly related note, the bumper (not sure of the name) above the left flipper seems to be going out about halfway through a game. It works great for half the game and then it just stops doing anything. When the ball hits, it's still triggering the jump sound and the score, but the solenoid no longer fires.

What the heck is up with this? I feel like with the random pop bumper, the flipper randomly dying and working again, and now this other solenoid just giving up halfway through a game (it works after I restart the machine)

I went ahead and just ordered the rottendog A3 board replacement. It might not fix anything or it might fix everything... all I know is it's cheaper than paying someone to diagnose it and possibly fix it. I'm figuring it would cost several hundred dollars to get it fixed if I give up trying.

I should probably try out the mosfet force firing thing and see what result that gives me. Thanks!

Thanks for the followup advice! I'll get around to grounding the mosfet to see what that does. As far as the pop bumper switch having problems... I don't think it's to blame. I can trigger the score when it's touched pretty easily and consistently.

I *could* tinker with it for hours figuring out what's wrong but I honestly bought this with the hopes of just having it work and being able to enjoy it. I have other projects I'm working on and this one is just supposed to be what I play to relax. Otherwise I would hold off on buying a new board and all that.

How exactly do I ground the mosfet in order to force fire the solenoid?

Okay, tested the mosfet by shorting it to ground. It fired every time without fail. So what does that mean?

I would assume that means the contacts for the bumper aren't good or something... but then... why doesn't it fire in test mode? I assumed in the solenoid test it would trigger the coil directly. Plus when I manually touch the bumper it's just not firing most of the time when the game is running. so it's like a disconnect somewhere...

Okay I just played a game and everything fired perfectly. I went into test mode and the bumper is firing perfectly... LOL I DUNNO.

So yeah um.... I guess grounding the mosfet fixed it somehow? No clue. I'm happy it's fully working though. I'll play it more and see if it keeps working or what... Thanks everyone for the guides and the help!

I still have the rottendog replacement board coming. I'm fine with just holding on to it for long term (I don't plan on selling this cab) or just selling the new board for what I paid.

They are pretty toasted... one of the pads is just totally gone. It's hanging on by a thread... I guess maybe that's it.