(Topic ID: 327596)

Evel Knievel Switched Lights Not Working

By Bruno63

3 months ago

Topic Stats

  • 9 posts
  • 4 Pinsiders participating
  • Latest reply 89 days ago by wayout440
  • No one calls this topic a favorite


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#1 3 months ago

My Evel Knievel pinball machine stopped working awhile ago. When it was turned on the GI lights would come on, but there was no power up tune and the game would not play. I found that the Self-test LED on the MPU module would only flash 2 times instead of six, which indicates a bad MPU module. The MPU board did have battery acid damage at the bottom when I bought the machine, so I mounted a new battery remotely and the game played fine for years like this. I decided that it was better to buy a new replacement MPU board rather than fix the original. I ordered the Alltek Systems Ultimate MPU board along with the lamp and solenoid driver boards.
I started the repair by installing only the new MPU board and this fixed the startup trouble and allowed me to play the game, but the switched lights did not work. I installed the new lamp driver board and solenoid driver board, but the switched lights on the playfield and backbox still would not light up.
I started checking the bulbs and sockets and didn't find any problems with them. I checked the pins and connectors on the boards and didn't find any corrosion.
The self test LED's on the new boards indicate that they are working. I saw a video on YouTube showing how to check voltages at the test points on the transformer rectifier board. Here is what I found:
T1-.04v dc Should be 5.4v
T2- 233v dc Should be 230v
T3- 15.6v dc Should be 11.3v
T4- 6.9v ac Should be 7.3v
T5- 45.8v dc Should be 43v
You can see that the reading at T1 is very low. Looking at the wiring diagram for the power transformer module shows that the T1 location leads to the J1 Playfield connection #7 which is for the SW. ILL. BUS and also to the J3 Backbox connection #6 also for the SW. ILL. BUS.
Is this the most likely cause of the switched light problem I'm having. If so would it be better to replace the rectifier if it is bad or order a new rectifier board.
The wiring diagram shows 4 rectifiers, but I only see two on the board and one mounted remotely above the board on the side of the backbox.
The photos of the rectifier board shows what I'm talking about, and the wrinkled appearance on the back side has me worried.

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#2 3 months ago

One of the bridges is made of discrete diodes on the top side of the board (circled in red below). The wrinkled appearance is not a problem, many will look like that, in fact I think all the Bally games I had looked like that. What usually is a problem is all the through holes. The lands around the hole crack, or around the leads, sometimes not easy to see. The usual fixes involve jumpers over bad traces, plus there should be additional jumpers added to this board as described on the pin repair sites to increase reliability. Plus all the male pin headers on the board should be replaced. The bridges should also be upgraded to higher amperage.

In short, for a small amount of money you can buy all the parts to overhaul this board and spend a good day or two, depending on your experience level and overhaul this board. It's not really much more expensive to buy a replacement board and be done with it - if you so desire.

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#3 3 months ago

I don't have much experience fixing circuit boards other than re-soldering some bad connections on the original solenoid driver board years ago. Replacing one of the rectifiers is something I could handle, but the board rebuild you described is more than I would want to tackle. Plus with a new board, I would have the confidence that all the components would be up to date.
What I really want to know is if the low voltage at the T1 test point is the definite cause for the switched lights not working, or could there be another reason.

#4 3 months ago

Yes most definitely the fact you don't have at least the recommended 5.4VDC at TP1 is why you don't have any switched illumination, but, and I need to put the but because there is the points of connection where the SI meets the playfield and backbox and the plugs themselves. The headers have been changed on the rectifier board, but were the pins replaced also?

You could try checking the fuse holder F1 that it is in fact securing holding fuse, also checking the fuse itself.

Honestly with the bridge being mounted the way it is off the board and the trouble revamping the old board, IMO get a new aftermarket one.

#5 3 months ago

I did check for continuity across the fuses and visually inspected them and they are all OK. I will be ordering a new rectifier board. I see that there is a solderless one available and I will try that one for ease of installation over a solder in type. This will at least get the correct voltage going out from the board and then I can check along the wiring path for any other problems if the lighting issue doesn't go away.
Thanks for the help.

#6 3 months ago

I think you answered your own question. No meaningful voltage at TP1 is your problem. The other voltages are good.
Three possibilities here, F1 is blown, BR1 is bad, solder connection to BR1 is open.

Check F1 with a meter to be sure, don't rule out the possibility the fuse clips themselves have worn out.
Inspect the solder connections to the bridge, if in doubt, resolder them.
As a last resort, replace BR1. Most like that is the problem but removing the board and replacing the bridge is a tough job for a newbie so I would exhaust the other possibilities before that.

#7 3 months ago
Quoted from wayout440:

One of the bridges is made of discrete diodes on the top side of the board (circled in red below).

The 1n4004 diode bridge is for the displays and definitely not the issue here as the HV is measuring correctly over 200v.

#8 3 months ago

I ordered a new Alltek no solder rectifier board since all the other boards have been replaced with new ones, so I at least have confidence that the backbox electronics are in working order. I removed one wire at a time from the old board and labeled them E1 through E12. I did the repair with the transformer removed from the backbox. The Alltek board is clearly labeled for each wire location and the no solder design made for an easy fix. The switched lights are working except for a few at the bottom of the back glass that I don't know what they are meant for and one on the play field. I hope this is just a case of dirty sockets or bad bulbs. I'll do more troubleshooting to try to fix the few remaining lights that don't work.

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#9 89 days ago
Quoted from BigAl56:

The 1n4004 diode bridge is for the displays and definitely not the issue here as the HV is measuring correctly over 200v.

I know that...just answering his question why he saw only three bridges compared to the schematic that shows four.

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