Fathom playfield fuse blowing

[Crashramp]

Hi guys,

I'm having a bit of trouble with the 1amp playfield fuse blowing as soon as the game is turned on. I don't know if this has anything to do with it but I had another problem which started at the same time.
I have a switch linked to one of the two micro credit switches which I've never had any issues with but last night I pressed the credit button and it was like the button was stuck on as it racked up 40 credits in quick succession and then kept trying to add them. I swapped the button but it made no difference. I then activated the two micro switches by hand and it turned out the second one with out the button attached was causing the issues. I've now swapped this switch out and no more credit adding but the fuse continues to blow each time I start the game. I'm not sure where to look here. There doesn't seem to be any coils locked or anything like that though.

This is the coin door setup.

[Strangeways]

Sounds like a coil / coil diode is measuring a short. With a multimeter, test each coil and anything that measure under 2 ohms is seen as dead short which will blow the fuse. Check that you are also replacing the exact same fuse value - I think they are 1.5 ohms slo blo - check the schematics on the wiring page.

Front door looks like a coincidence. Get rid of the button and set the game up to give first credit at 10,000 points - you will never need to open the door again (except to look at it) 

[Pintoxicated]

Well I wouldn't offer any assistance anyway until you had cleaned that coin door up a bit.....sheesh, I wouldn't even be able to see myself in it

[Boots]

Does the credit knocker fire when credits are added on this machine?

Perhaps it got hot when the credits were racking up???

[pinball god]

+1 to setting a low score for a game. No need for extra switches or buttons

[Crashramp]

Sounds like a coil / coil diode is measuring a short. With a multimeter, test each coil and anything that measure under 2 ohms is seen as dead short which will blow the fuse. Check that you are also replacing the exact same fuse value - I think they are 1.5 ohms slo blo - check the schematics on the wiring page.

Front door looks like a coincidence. Get rid of the button and set the game up to give first credit at 10,000 points - you will never need to open the door again (except to look at it) 

Thanks Nino,

I'll test the coil diodes as suggested.
The button will stay though, I love the call outs when adding credits on these old Bally's. I get great entertainment out of Synchronising credits between Fathom and Xenon. Small things amuse small minds I know but I still find it funny.

[Pintoxicated]

And don't forget to clean the inside of that bloody coin door whilst you are at it.

[Crashramp]

And don't forget to clean the inside of that bloody coin door whilst you are at it.

Yes it's shameful I know. I'll get to it one of these days.

Does the credit knocker fire when credits are added on this machine?

Perhaps it got hot when the credits were racking up???

No, no knocker for the credits. There is just a call out. A very masculine "Ahh Yes". For anyone wondering Xenon's is woman moaning "Ahhhh". Like I said, small things! 

[pinball god]

And don't forget to clean the inside of that bloody coin door whilst you are at it.

Yes it's shameful I know. I'll get to it one of these days.

Does the credit knocker fire when credits are added on this machine?

Perhaps it got hot when the credits were racking up???

No, no knocker for the credits. There is just a call out. A very masculine "Ahh Yes". For anyone wondering Xenon's is woman moaning "Ahhhh". Like I said, small things! 

sounds like my wife must be broken. I get no sounds when I push her buttons. Think I'll need to troubleshoot a bit more.

[Ballywannabe]

As Nino says, it must be a playfield short. Look for coils with low resistance as suggested, but also look for shorting to coil lugs.  Does fathom have small coils to drop targets?  If so don't forget to check these, as they can be a problem.

[Crashramp]

A new switch fixed the credit adding problem and I'm getting closer to finding the cause of the blown fuse. I'm probably doing something wrong here but the coils with the single diode read just fine but I don't get a reading at all from the ones with the double diodes. This made me change my tact a bit. When I rebuilt the assemblies on this game I added connectors to them so I could remove them easily if I ever had trouble with something. Anyway I unplugged them all and went back into the solenoid test in the games self test mode but it didn't take long to realise that with the playfield up they all worked and with the playfield down I'd instantly blow the playfield fuse.
See the picture below because this is how close to closed the playfield can be and the fuse is fine. Close it up the last couple of center meters and there goes the fuse. Something's shorting here, I just have to find the culprit.

[benpin]

 When playfield fully closed.

 Check to make sure the playfield not touching flipper switches?

[Crashramp]

When playfield fully closed.

 Check to make sure the playfield not touching flipper switches?

That's what I was hoping to find. Something nice and easy to see and get to but the switches are clear. Still haven't tracked it down but im sure it's going to be something simple like that.

[Strangeways]

Reminds me of an issue I once had with a Fathom. Every time I closed the headbox door, the GI would dim and then blow the GI fuse. It turned out the grounding strap was too long and was shorting out the GI.

You have a wire from a coil, shorting to ground. Move the wires on the inside of the cabinet simulating a lowered playfield. See if the fuse blows.

[Crashramp]

Thanks Nino,

I'll give that a go tomorrow. I have to make a quick stop into Jcar tomorrow. I've run out of fuses tonight.