Model 873 Blowing 110V fuses

[big_e]

Ive got an 873 I am trying to fix for a friend.  Works great until you close the door and then the fuse on the 110 side is toast.
Obviously I went through all the wires on the hinge side of the door assuming I would find something worn through, but did not.  Its frustrating.  I think I am going to wire in a circuit breaker so I can reset it each time rather than having to replace a fuse.
In the meant time, any thoughts on the culprit?  If its door mounted it could only be fluorescents right?
ThanksE

[rjpohl]

I had one that a wire on one light socket touched frame.  Just had to rotate it.  It was on the side opposite hinges.

[DavidLee]

Did you try insulating the wires from the door frame with some tape?
Try closing the door slowly as a reference to when the fuse blows.
With the door open physically move the wires to simulate door closure.

The wire bundle at the frame may have a bare wire or two.
Rotate the bundle as to get a good look, orange, red and lighter brown wires may appear okay.
As the copper is harder to see when exposed on these colors.


In the hinge area, these wires make a lot of movement and can wear through.
Also the 110 v transformer wiring could be effected by the door closing.

[wolftalk]

if you can't find it and don't have a schematic, what's the complete model number on the plate below the handle?


many of the 873's don't have a lot of 120V circuits on the door - just the two fluorescent lamps, the starters and the ballasts for them.


the pinball guys often solder a pushbutton circuit breaker to a blown fuse.  One of these things:
https://www.amazon.com/uxcell-Thermal-Overload-Protector-Circuit/dp/B07NRX34S5


if you had more time to wait for shipping, you can get them on aliexpress.com for around 0.70 each, and those vendors will have lots of amperage values so you can get a 3A, 5A, 10A, etc. assortment for a few bucks.  e.g.
https://www.aliexpress.com/store/3019003


while you can solder the blown fuse directly to the breaker terminals, that may be a problem if the fuse holder is blocked by something.  I prefer to solder wires to the fuse and put 6.3mm female terminal connectors on the wires like these:
https://www.aliexpress.com/item/32826497604.html


that'll let you swap the breaker for whatever amperage you need.

[RiseLikeRa]

Big E:


A short in the door is a perfect opportunity for my lights out short finding method.  Get the room, and the game as dark as you can and then shut the door.  Look for the small arc.  There is your problem wire.  Case Closed, pun intended.


Ra

[DavidLee]

Good advice Ra.


Also look on the front of the reel mechanism chassis and latch handles for any burn marks.

[RiseLikeRa]

David I am amazed by you and some others on this list. The way that you guys dive deep into a problem makes me look like a surfer for sure.  With no formal training or engineering background I try to stay in my lane and keep it simple.


Sometimes it works.   When it  doesn't I reach out to you big guns.  I am forever grateful.


Ra

[big_e]

Thank you all for the advice, I will try all of these later.

I grabbed a 3A breaker from the shop where I work.  We build control panels so they are in ample supply.  I will wire that in place of the fuse so I can quickly reset.
Next Ill do some high level looks for bare wires in the bundle that goes around the hinge.  If I cant find it I will wait til its dark and slowly close door and see if it stands out.
I appreciate you all.  Merry Christmas!
E

[OldReno]

If it’s not in the door, then pull out each unit one by one & see which one blows the fuse. It may not always be a 120v short that blows the main fuse. Also unplug each of your 2 molex door plugs & see which one is making it blow.
There are some writings on checking for shorts somewhere here.
With machine unplugged check on ohms for a short to case. Machines are designed with case ground only, and no circuits connected to case. Check shorts to case especially with 20,30 and 70 wires. Or you can do it with power on if you’re comfortable with your VOM on A.C. 
We used to quickly rake a pocket screwdriver touching to case to check those 3 wires when working on the floor. The size of the spark could tell you if it was a 120,50, or 6v short.
But ya hadda be quick...lol.