Bally Strikes and Spares (Bally, 1978) f4 fuse blows

[jlafleur02]

I have a ballys strikes and spares pinball machine. About every day the f4 fuse blows. Where should I start to look for the problem and can I just keep replacing the fuse? It is a 5amp fast blow fuse. Not sure what it controls. I have a schematic of the board but can make heads or tails from it.

 

[jlafleur02]

Ok so the fuse blows if I hold the right flipper down. I checked the cabinet switch and it is corroded. The coil gets really hot so I am assuming the switch is bad. I am ordering a new ag-25-500 coil and switch. I will let you know how it works.

 

[Coil_Smoke]

A quick look at your schematic shows 49 VAC secondary winding going through F4 to power playfield coils. There is a flipper disable coming from driver board that I guess supplies or denies power to flipper switches. What I'm on about is I think all flipper power is going through your flipper switch contacts and not some driver transistor. It also shows blocking diodes across both power and hold coils(windings ) 2 diodes for each flipper solenoid. So getting the switches clean and adjusted is important. The End Of Stroke switch needs to open when the flippers reach the end of their travel. If the EOS contacts stay closed your solenoids will over heat.
http://www.ipdb.org/machine.cgi?id=2406

Some discussion of EOS issues @ Old Chicago weak flippers and pop bumpers - Pinball Nirvana Forums

 

[jlafleur02]

So i am buying a new cabinet switch and aq-25-500 coil. I will replace. Do you think this should take care of It?. I believe it will. It definataly seemed like the coil was under constant power. When I held the flipper button down. I did replace fuse and It didn't heat up until I played it. When I hold the button down to try to keep the ball on flipper then direct my shot is when the fuse would blow.

 

[Coil_Smoke]

That all sounds very much like switch and coil issues. Yes EOS switch not opening would heat up a coil...But...would it blow a fuse? I don't think it should. The fuse blowing points to a bad coil winding. Possibly shorted and drawing over-amps. EOS contacts can be problematic. They can be cleaned more aggressively than the silver contacts which are common to arcade machines. They usually benefit from use and may improve flipper power with more play time. Never use chemicals on contacts. EOS contacts Handle all coil power until they open.So replacing the coil and switch + getting the EOS switch right should get you going again. Pay close attention to those diodes and make sure they stay pointed in their "One Direction"...C_S