Bally -54 Rectifier Board 12 volt problem

Help! This is driving me crazy. I rebuilt a -54 rectifier board (I have rebuilt several others with no issues) from a Xenon and TP3 is reading over 30 vdc. The board had some prior work and still had the original 3 amp diodes for the 12 volt rectification. I tested it before I started and it read about 15 volts at TP3. I replaced the original diodes with 3 amp 1N5404 diodes.

I have done the following:

* I reflowed all of the connector pin solder. There are no shorts in any connectors (tested with DMM).
* All of the 5404s pass the diode test (they are all new).
* I can detect no shorted traces anywhere on the board (tested with DMM).
* Confirmed about 15 vac at the unbanded ends of CR6 and CR7.
* Got over 30 vdc at the banded ends of CR6 and CR7. Cut the trace to TP3 and still got over 30 vdc.

Help!

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#2 5 years ago

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Quench

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Quoted from FiatsRUs:
* Confirmed about 15 vac at the unbanded ends of CR6 and CR7

.
The unbanded end of CR6 is the wrong location to measure AC. You need to measure AC across the unbanded ends of CR5 and CR7.

RectifierBoard-54.jpg

#3 5 years ago

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FiatsRUs

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Quoted from Quench:
.
The unbanded end of CR6 is the wrong location to measure AC. You need to measure AC across the unbanded ends of CR5 and CR7.

[quoted image]

That's interesting. I believe the schematic you posted is incorrect. I checked my Xenon manual and sure enough it has the same one. Here is the schematic from the EBD manual (it also has a -54 rectifier board). I am confident it is correct. Follow the traces in the pictures I posted and you'll note on the back side of the board that the banded ends of CR6 and CR7 are connected and the trace leaving that connection goes to TP3 and J3-10.
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#4 5 years ago

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Quoted from FiatsRUs:
That's interesting. I believe the schematic you posted is incorrect. I checked my Xenon manual and sure enough it has the same one. Here is the schematic from the EBD manual (it also has a -54 rectifier board). I am confident it is correct.

Good catch!
The game you linked was Xenon so that's the one I looked up. It appears Flash Gordon (which came out next after Xenon) also has those diodes marked the wrong way around in the schematic.

Remove the 4A fuse at F3, do you still measure any voltage at TP3?

#5 5 years ago

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barakandl

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the diode re-arrangement mixup compared to the schematic probably happened when bally added holes so a complete single package bridge rectifier could be used.

#6 5 years ago

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Quench

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Funny thing is that Fathom also has the correction in the schematic, but every game schematic after it reverted to the wrong diode numbering even the last game on this platform Cybernaut which came out in '85 and its rectifier board schematic was redrawn.

#7 5 years ago

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Buzz

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Very interesting to me and all I can say is all you guys are the shit. So much great sharing of information. I love it.

#8 5 years ago

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LOTR_breath

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This is interesting. One thing is for sure. A working bridge can't turn 15 vac into 30 vdc. Something strange going on maybe on the input side?

#9 5 years ago

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barakandl

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Quoted from LOTR_breath:
This is interesting. One thing is for sure. A working bridge can't turn 15 vac into 30 vdc. Something strange going on maybe on the input side?

with no load on 12v it will probably read high.

#10 5 years ago

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FiatsRUs

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Quoted from Quench:
Remove the 4A fuse at F3, do you still measure any voltage at TP3?

I'll do this tonight and see what happens.

1 week later

#11 4 years ago

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FiatsRUs

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Quoted from FiatsRUs:
I'll do this tonight and see what happens.

Finally got around to this. Here is some reference data from a working Xenon (I have two of them):

With a load: TP3=15.2 vdc, 13.9 vac measured at the unbanded ends of CR6 and CR7
Without a load: TP3=15.3 vdc,
No load and NO FUSE at F3: TP3=12.8 vdc, 17.2 vac at the unbanded ends of CR6 and CR7

Here is the board in question:
No load: TP3=35 vdc, 15 vac at the unbanded ends of CR6 and CR7
No load and NO FUSE: TP3=25.5 vdc, 15.9 vac at the unbanded ends of CR6 and CR7

How can there be any voltage with the fuse removed, on either of the boards?

#12 4 years ago

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Quench

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Quoted from FiatsRUs:
How can there be any voltage with the fuse removed, on either of the boards?

There's got to be a short circuit on the board and judging by the voltage I'm guessing with half the phase of the solenoid voltage.
Since the output of that bridge circuit at TP3 only goes to pin 10 of the J3 connector, with the machine off set your multi-meter to continuity mode, put one meter lead on TP3 and touch the other meter lead all over the rectifier board until you measure continuity to something other than CR6 and CR7.

A close visual inspection should also reveal the short. Post some clear high res pics of the board if you need some more eyes to look at it.

#13 4 years ago

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Billc479

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I know this sounds way off base, but is it possible someone re-wired the secondary transformer leads and got them mixed up? Check the secondary winding connections to rectifier board connections.

#14 4 years ago

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FiatsRUs

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Quoted from Billc479:
I know this sounds way off base, but is it possible someone re-wired the secondary transformer leads and got them mixed up? Check the secondary winding connections to rectifier board connections.

Everything on Xenon #2 (the one with the issues) worked fine, and the game booted and played, until I "fixed" the rectifier board.

Note that for Xenon #1 (the working reference machine), there is a reading with fuse F3 pulled. How is that possible? Could someone try that on their machine and report results?

Quoted from Quench:
There's got to be a short circuit on the board and judging by the voltage I'm guessing with half the phase of the solenoid voltage.
Since the output of that bridge circuit at TP3 only goes to pin 10 of the J3 connector, with the machine off set your multi-meter to continuity mode, put one meter lead on TP3 and touch the other meter lead all over the rectifier board until you measure continuity to something other than CR6 and CR7.
A close visual inspection should also reveal the short. Post some clear high res pics of the board if you need some more eyes to look at it.

I'll get some more pics posted. I get what you are saying but I have used a DMM to test for shorts all over the board.

2 weeks later

#15 4 years ago

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FiatsRUs

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Quoted from Quench:
There's got to be a short circuit on the board and judging by the voltage I'm guessing with half the phase of the solenoid voltage.
Since the output of that bridge circuit at TP3 only goes to pin 10 of the J3 connector, with the machine off set your multi-meter to continuity mode, put one meter lead on TP3 and touch the other meter lead all over the rectifier board until you measure continuity to something other than CR6 and CR7.
A close visual inspection should also reveal the short. Post some clear high res pics of the board if you need some more eyes to look at it.

I double and triple checked. No continuity except where it is supposed to be. You can see in the pics that the area of the board behind the large diodes his discolored and has been hot. I doesn't appear to be burned to the point of causing issues. I have checked continuity between all of the pins of the input and output connectors. No errors.

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#16 4 years ago

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Quench

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Have you got an oscilloscope? It will tell you the whole story.

If not, at this point I would hook up a load and remeasure the TP3 voltage. Use a 12V lamp something around 12W, 1 amp as a load connected between the GND and TP3 test points.

#17 4 years ago

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FiatsRUs

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No scope. I'll try a load. Will a #906 flashlamp work?

#18 4 years ago

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Quench

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Quoted from FiatsRUs:
Will a #906 flashlamp work?

Yes, a #906 incandescent globe should be fine.

#19 4 years ago

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barakandl

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Could it just be the 12v supply is basically unloaded and 12000uF on driver board capacitor keeps the voltage up way high and thats what the DMM shows?

#20 4 years ago

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FiatsRUs

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I don't get it, but it reads normal with the load (the light on) and still at 35 without (light unattached). I guess I'm good to go.

Thanks to all.

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#21 4 years ago

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