(Topic ID: 244053)

Evel Knievel: Bally rectifier board, bad TP3


By Brewchap

85 days ago



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  • 43 posts
  • 5 Pinsiders participating
  • Latest reply 51 days ago by Quench
  • Topic is favorited by 4 Pinsiders

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#2 85 days ago
Quoted from Brewchap:

test point 3, which only has 6 DC volts and needs to be 11.5 DC volts

Half voltage usually indicates a faulty bridge rectifier with one of it's internal diodes going open circuit. It's bridge rectifier BR2 in this case so you're on the right track.

With the machine off, disconnect the J3 connector from the rectifier board and do a diode check on that BR2 which basically has four internal diodes.
If the board is in very toasty condition you might need to resolder the bridge.

1 week later
#5 78 days ago

What's a diode test with your multi-meter saying about the replacement bridge?
What are you measuring at TP3 when the J3 connector (backbox harness) is disconnected from the rectifier board?

#7 78 days ago
Quoted from Brewchap:

Going by the picture

Nice pic, you have another dud bridge rectifier. Two open circuit internal diodes, both on the same cycle.

#9 77 days ago
Quoted from minnesota13:

Test Point 3 is supposed to be 5VDC....................Not 11.5. Test point 1 should read the same as TP 3. Test point 5 is the input to the 5V regulator circuit and should read 11.5 or thereabouts.

We're talking about the rectifier board, not the solenoid driver board.

When J3 (backbox harness) is NOT connected to the rectifier board, TP3 on the rectifier board should measure around 11.9 volts.
When J3 is connected to the rectifier board, TP3 on the rectifier board will now measure between 14.5 volts and 16.5 volts thanks to the large capacitor at C23 on the solenoid driver board.

2 weeks later
#15 59 days ago
Quoted from Brewchap:

I just replaced Fuse F4 after I found it blown, and it blow again telling me that BR2 is bad again.

Are you actually measuring any short circuits across any BR2 pins?

Does rectifier board test point TP5 measure a dead short to ground? If yes the problem might be downstream from the bridge. Check the coin lockout coil on the coin door and make sure the green wire isn't also touching the coin door frame.

#18 59 days ago

Yeah sorry, BR3 is the solenoid bridge that's fused by F4.

What bridges are you using?

Are you by any chance overheating them for too long when soldering them?

#20 58 days ago

Not sure if it helps, but I always solder the bridge after screwing the bridge to the rectifier board/plate, and also wait at least 5 minutes between soldering each leg.

#24 52 days ago

Does it happen if you disconnect J4 from the SDB (Solenoid Driver Board)?

#33 52 days ago
Quoted from Brewchap:

I have to pull J1 and J5 from the SDB to keep the solenoids from locking on.

With these two connectors removed:

* What voltage are you measuring at TP3 on the SDB?
* what voltage are you measuring at pin 24 of the U2 chip on the SDB
* Is the flipper enable relay clicking on at powerup? i.e. do the flippers always flip when you press the flipper buttons regardless of being in game over mode?

#35 52 days ago

Sorry, I just re-read your posts and you mentioned it's all working properly again. So those three diagnostic questions I asked are only relevant when the game is locking on the coils at powerup.

The only way all coils can lock on at powerup is a failure of some sort with the 74L154 chip at U2 on the SDB. I would carefully inspect the solder joints of pins 12 and 24 on that chip which is ground and 5V power respectively. Follow the connection between pin 24 to TP3 since it goes through some jumper links and carefully inspect their soldering too.

#37 51 days ago
Quoted from Brewchap:

Could that cause failure of the Q3 and Q7 transistors? I believe that is for the knocker and chime since they dont work. It seems like they fail as soon as I turn the power on.

When do those transistors fail? At first poweron after replacement, or first activation during attract/game mode?

#40 51 days ago
Quoted from Brewchap:

Is this wired right? I'll clean up the solder job in a bit.

Yes, the green wires go to the coil lug where the banded side of the diode is.

If the transistor driving that coil keeps blowing, the coil diode might be shorted. Before you solder that white wire on the other coil lug, measure the resistance across the coil - should measure around 53 ohms. If you measure a dead short circuit, replace the diode on that coil. Also check that the diode is properly soldered because if one leg isn't, the transistor will always blow on first activation of that coil.

You might just want to replace the diode on that coil anyway.

#43 51 days ago

Hmm, if you still have the diodes that were removed from the coil, measure if those diodes are shorted. The problem might actually be an intermittent short in the coil winding..

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