williams firepower blowing fuse

[bikerman]

Hello, I am hoping someone can help me with the problem I am having with my pinball machine. I bought it a couple weeks ago and it had a couple of blown fuses. The one problem was it had a bad bridge rectifier, changed that and not blowing that fuse. The other fuse 2-1/2 amp is for the solenoids I believe, I read some place and said to test the transistors. I found a bad one and changed out. It will work now for a couple of games then the machine " freaks out" the displays have numbers that make no sense and it blows the fuse. I have run the solenoid test and they all appear working fine. I can change the fuse and it works for a while again. 

[slotsteve]

bet you have a dieode off a coil do a coil test and see when fuse blows which coil fired b4

[dragster73]

Based on the "Freaks out" statement i would bet that part of the problem is due to the EPROM sockets. Are they original? Secondly, the problem could be caused by the interconnect where the two boards plug together. Are they original?, any signs of prior acid damage from batteries leaking? Are the boards screwed down or are they hanging loosely?

Does the game have the original 6 ROMS in it or has it been converted to three EROM's? The original software had a bug in it that could cause lock ups and freeze ups.

What it the +5 volts at the CPU board? This could also be a reason for it acting up.

Are there any burnt connectors anywhere that are visible?

I repair these style Williams boards all the time. The most important thing on them is replacing the old sockets with new ones to assure proper connection to the socketed chips and secondly the interconnect between the driver board and the CPU.

Answer thees questions and by processes of elimination maybe we can  figure out which direction you need to head in.

[BR549 Auto Sales]

Would be a good idea to re flow the solder joints on the bottom of the CPU and all around the solenoid driver board, most that I have repaired in the past had cold/cracked solder joints. Would be a good idea to re cap the power supply as well

[bikerman]

I will try reseating the EPROMs. Everything appears to be original, there is no acid around the batteries. I have had the two boards apart and the connector looks good no burn marks. The boards are just hanging, no screws in it when I got it. I will also check the solder joints tonight also. Thanks for a starting point. I will try these things tonight

[dragster73]

Reflowing the pins around the boards most likely isn't going to solve the problem of it "Freaking out"

It probably isn't going to hurt anything but most likely will not solve anything.

A simple test for the power supply is this.

Put your DMM to "AC" and test the +5 volts using the "AC" test. You should basically have NO "AC" voltage. If this is the case then the CAP is fine. IF you were to get a Reading of .3 volts then you may want to consider changing the cap. Usually a board will no longer run once the "AC" voltage reaches .5 volts "AC"

Again Changing the CAP is probably not going to fix this problem unless he detects some sort of problem with the voltage.

99% of these boards have problems due to connectors.

[slotsteve]

they need to be screwed to back box for ground that might be your trouble

[bikerman]

Do you know off hand what size screws?

[dragster73]

I will try reseating the EPROMs. Everything appears to be original, there is no acid around the batteries. I have had the two boards apart and the connector looks good no burn marks. The boards are just hanging, no screws in it when I got it. I will also check the solder joints tonight also. Thanks for a starting point. I will try these things tonight

A good start would be putting some screws in it. The boards flopping around are not going to help where they plug together. Pushing on the EPROMS will be a temporary fix as the EPROM sockets are original then they will need to be replaced.

[dragster73]

Do you know off hand what size screws?

If you do not have the screws you could check the bottom of the cabinet. If they are not there i like to use 1/4" self tapping screws. This makes them easy to install and remove with your drill motor using a 1/4" magnetic driver.

[bikerman]

Thanks guys, I think reseating the eproms and grounding the board solved my problem. Thanks for the help. What is the best way to fix chipped paint on the play field? Also does anyone have an idea what my machine is worth? I am going to leave it sit on for a little while and keep trying it.

[slotsteve]

price depends on shape of game and playfield rough 500 near mint 1000

[bikerman]

Ok, my firepower has been working, now is blowing the solenoid fuse again. I removed a wire from each of the pop bumpers and it doesnt blow many more. My question is can it just be a diode? I think they are diodes that go across the contacts of the coil. Now they should only have continuity in one direct I believe. If i check across each coil should I have continuity?

[slotsteve]

yes with meter you should only get reading 1 way

[bikerman]

I get continuity in both directions with it attached to the coil. So just might be the diodes on all of them?

[slotsteve]

unhook  one end  to get true reading

[bikerman]

Ok, I caught the coil staying engaged on the one bumper, what would cause it not to release?

[slotsteve]

that would blow fuse   you mignt have bad transistor or points closed on  that bumper

[bikerman]

I have two bumpers that engage when the game is started and try don't release and blow the fuse. The contacts underneith are not touching. How do I test the transistor?

[bikerman]

I found a burnt resistor on the bottom of the play field but it looks like it is for the tilt. I am not sure though, here is a pic

[bikerman]

I changed the two transistors that were for the top and bottom left jet bumpers and didn't make a difference. Both bumpers lock down when the start button is pushed.

[carbyjr]

Still having problems ?
I have a Firepower and am very good at fixing that era machines