bally 1979 dolly parton pinball machine blowing playfield fuse

[Franklin Macneil]

ive got a 1979 bally dolly parton pinball machine and everytime i fire it up after boot all coils do initial fire up the playfeild fuse blows. replaced mpu and solenoid board. all connections look good. how would i narrow this down to the problem. it has to be a coil. im not sure how to test them if fuse will not quit blowing. i thought about disconnecting all power wires from all soleniods, and put power to one at a time while doing the mpu solenoid test. will this work or will it cause more damage. please this is drivng me crazy.

[John Robertson]

Post by Franklin Macneil
ive got a 1979 bally dolly parton pinball machine and everytime i fire it up after boot all coils do initial fire up the playfeild fuse blows. replaced mpu and solenoid board. all connections look good. how would i narrow this down to the problem. it has to be a coil. im not sure how to test them if fuse will not quit blowing. i thought about disconnecting all power wires from all soleniods, and put power to one at a time while doing the mpu solenoid test. will this work or will it cause more damage. please this is drivng me crazy.

Try disconnecting 1/2 of the coils by unsoldering just the single wire
going to those coils. Fuse still blows? Split the remaining coils in
half and unsolder just those few. Fuse blows? Repeat process...

Once the fuse stops blowing then you know the problem is in the group
you disconnected and study each solenoid closely looking for signs of
solder/wire shorts, discoloured coils, etc.

On ohmmeter is the best way to test though - check across each coil to
see what the resistance is. Use my chart to see what the resistance
should approximately be:

https://flippers.com/coil-resistance.html

Let us know what happens!

John :-#)#

[John Robertson]

Post by Franklin Macneil
ive got a 1979 bally dolly parton pinball machine and everytime i fire it up after boot all coils do initial fire up the playfeild fuse blows. replaced mpu and solenoid board. all connections look good. how would i narrow this down to the problem. it has to be a coil. im not sure how to test them if fuse will not quit blowing. i thought about disconnecting all power wires from all soleniods, and put power to one at a time while doing the mpu solenoid test. will this work or will it cause more damage. please this is drivng me crazy.

Try disconnecting 1/2 of the coils by unsoldering just the single wire
going to those coils. Fuse still blows? Split the remaining coils in
half and unsolder just those few. Fuse blows? Repeat process...

Once the fuse stops blowing then you know the problem is in the group
you disconnected and study each solenoid closely looking for signs of
solder/wire shorts, discoloured coils, etc.

On ohmmeter is the best way to test though - check across each coil to
see what the resistance is. Use my chart to see what the resistance
should approximately be:

https://flippers.com/coil-resistance.html

Let us know what happens!

John :-#)#