(Topic ID: 163554)

First real pin... troubles after one day of use

By Konidias

7 years ago

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#1 7 years ago

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!

#2 7 years ago

Bump for a first time pin owner. Anyone have advice on where to start?

#3 7 years ago

Hey Konidias,

A great place to start for this game, which is a Gottlieb System 3, is this repair guide:


#4 7 years ago
Quoted from Wolfmarsh:

Hey Konidias,
A great place to start for this game, which is a Gottlieb System 3, is this repair guide:

+1 Clay always has great guides online.

#6 7 years ago

Are the diodes associated the original coils broken or bad ?
Also check the End on stroke switch on the flipper mech. And check the wiring isn't broken somewhere.

But use the guides people posted and follow the steps to troubleshoot.


#7 7 years ago

Your pop coil/fuse issue is likely related to a shorted transistor (actually a Mosfet for your Gottlieb) on the solenoid driver board in the head.

The guide others pointed to will tell you how to test for a shorted Mosfet on the driver board, using continuity on your multimeter.

Your right flipper END OF STROKE switch is probably not making good contact. Test it for continuity using a multimeter. It will need to be shut (and making contact) when NOT ENGAGED, and open 1/8 inch WHEN IT IS ENGAGED.

If the E.O.S. is not making good contact, it will never work.
If the E.O.S. is not opening 1/8 inch upon firing, the fuse will quickly blow.

These are not problems that can really be blamed on the previous owner. It is actually part of routine maintenance on a pinball machine. Like changing the brake pads or oil in your car.

I wish more people would emphasize and disclose this information when selling a game to a first time buyer. Moving parts with high voltage and lots of heat are the enemy of most everything made that contains solid state electronics. Pinball machines are no exception.

The best advice I can give you is to think of a transistor/Mosfet in a pinball machine as a kind of fuse. They fail a LOT. And I mean so much that I buy most common pinball transistors, 100 at a time. They are designed to keep high voltage away from the PCB's that run the game. They are cheap (1$ or less) and designed to fail when a coil or diode gets a surge in voltage. Sometimes they just wear out after so many cycles or even with age, once they fall out of spec (like fuses). They can also TEST GOOD and just be bad when they are engaged. So, if you have one in question, just replace it. They are $1. (Cheaper than a single glass fuse these days!)

Regarding the Mosfets that run the coils in your SMMW, just order 5 of them (if you find one shorted) and you should have enough extras for however long you own the game.

#8 7 years ago

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.

#9 7 years ago

Who sold you the game and why wouldn't they offer advice or help you if the game stopped working the same day you bought it?

If you need a good pinball technician I have a couple referrals to choose from.

#10 7 years ago

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.

#11 7 years ago
Quoted from Konidias:

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.

Next step is to test for DC voltage at the flippers coil lugs in "game mode". Black lead on side metal rail of machine, red lead on each lug. Report what you find here.

All coils should have voltage on all lugs in "game mode". Don't just start replacing stuff. You'll be wasting time and money.

#12 7 years ago

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?

2 weeks later
#13 7 years ago

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!

#14 7 years ago

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?

#15 7 years ago

Have you run the coil test? See if the coil fires in that test if you haven't.

#16 7 years ago

A MOSFET cannot kill a diode on a coil unless it is installed backwards.

The MOSFET is simply a switch. They can fail in three ways:. They can open up (unable to pass any power). They can short out ( pass full power all the time - a good coil will energize the moment you turn the game on). Or they can partially short out allowing a small amount of power to always get to the coil. Not enough to make it kick but enough to eventually heat up and start to burn windings or melt the sleeve.

MOSFETS are extremely static sensitive so it is possible you damaged it when installing or even handling it.

On most systems, you can check all the wiring down to the playfield and the coil and the fuse by shorting the metal tab on the MOSFET to ground ( ground braid in the back box should do). If the pop bumper will kick, your MOSFET is bad.

Replace the MOSFET again.
Cut the diodes off and check to see if you still have 15 ohm's or more across the coil. If drastically less, the coil is now bad. If still 16 ohm's, make sure the plunger can move freely up and down in the coil sleeve.
If still 16 ohm's and smooth motion, install a new diode (check schematic for which wire received the band on the diode).
Apply power. Make sure coil doesn't immediately energize. If it does, you still have a short somehow on the driver board (IC that drives the MOSFET could be bad). If it does not immediately energize, immediately check for any voltage across the coil ( there should be zero!). If some voltage, you will burn up the coil again.

FYI, the most common scenario is: diode across coil fails (either open or short), shorted immediately kills MOSFET on next energizing of coil. If open, back EMF from coil kills MOSFET (shorts out). Shorted MOSFET keeps coil energized. Coil melts, ohm's value greatly reduces as windings begin to short. Reduced ohm's means more current. Excess current blows fuse (or burns hole in PCB under flaming MOSFET.)

#17 7 years ago

As to your flipper, if it fails again. Open up the machine, start a game, push in the flipper button and then raise the flipper by hand. Let go of the flipper still holding the button. If flipper stays up, you have bad contacts or a misadjusted EOS switch as others have already stated.

#18 7 years ago

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!

#19 7 years ago

Cold solder joint on a connector pin or maybe even the transistor.

#20 7 years ago

Have you messed with the switch on the pop bumper?

#21 7 years ago

I'd definitely follow Cactus Jack's advice and try very briefly grounding the mosfet. If the coil fires consistently, you know the coil is still good and the wiring from the coil to the driver board is good.

I'm also thinking it might be the pop bumper switch. Maybe a bad or broken wire connection to the switch(es) on that pop bumper's switch stack...or misaligned/improperly gapped/dirty switch contacts... I'd access the switch test in diagnostics and make sure it's recognizing the pop bumper switch activation consistently. If it works properly repeatedly in the switch test, then I'd keep looking at the coil and driver side of the equation.

Study up on Clay's guides/Pinwiki for Gottlieb System 3 games (the series SMMW is part of) and follow the sage advice from Cactus Jack above. As frustrating as this experience may be, it's an excellent opportunity to learn. It's an unfortunate fact that owning a pinball machine entails learning how to service it, or paying to have someone come fix it for you.

Btw, there are a number of excellent circuit board repair services offered by a few members here if you decide to try having it fixed. Might cost less than you're expecting...

If i lived closer, I'd volunteer to come check it out for you. I'd love to get some time in on that game!

Good luck! I hope to see you get this working properly soon.

#22 7 years ago

Always check the simple stuff first. Too many newbies jump to replacing boards -- when in reality, most problems are connectors, mis-gapped or dirty switches, or a loose wire that shorts out intermittently.
As mentioned above, Clay's guides are excellent.

#23 7 years ago

You ordered a rottendog board? Take a deep breath! I don't think you have a board problem.

Have you fired the coils and bumpers in test mode? I ask because you said one was firing occasionally and as another poster mentioned it could be a switch issue.

Don't throw a 200-300 board into this game until you have verified you have a board problem. Have you read through the guides yet? Shorted the transistors?

#24 7 years ago

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.

#25 7 years ago

Keep in mind that scoring on the pop bumper and firing of it are two separate processes the latter of which can and usually does have several non board issues.

Here is my fear for you: your game components are bad (likely cause) and you will stick a new expensive board in that will get damaged immediately leaving you in the exact same spot except a few hundred dollars poorer. It's your game - and I 100% relate to wanting to get it running quickly but pinballs require troubleshooting that arcade games do not. I have the full size Mario... so I know System 3s. Run through the guides troubleshooting to shore up your cabinets parts before you put that board in.

Happy to help no matter what you do...

#26 7 years ago

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

#27 7 years ago

Alligator clip on tab of transistor and other end on metal part of cab or ground test point of board.

The guide linked earlier walks you through it in greater detail along with how to test coils.

#28 7 years ago

Don't hold the wire on too long - just a second to see the part fire (or not fire,,,)

#29 7 years ago

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...

#30 7 years ago

You have now confirmed that you likely have a bad MOSFET... at the very least. I recommend going back to Cactus Jacks post and replacing the mosfet again...

Also make sure in switch test the bumper switch is working consistently. If it is - this is more evidence that the mosfet and or coil/diode may be your issue.

I think you will find it is either the mosfet alone or the mosfet/coil/diode. The guide walks you through testing. Remember - a bad coil/diode will kill a new mosfet. Circular problem...

#31 7 years ago

And to answer your question - a bad mosfet means it isn't passing power from the board to the coil and this is why it doesn't fire in test mode. When you ground it you force power through it.

#32 7 years ago

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.

#33 7 years ago

Is it possible the MOSFET solder joints are bad/weak?

#34 7 years ago

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.

#35 7 years ago

There you go... Probably need to add a trace wire. Easy fix.

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