Bad bridge rectifier in the backbox.

Do you happen to know which one? I have the Inkochnito's Bridge Board for the power. Could that be failing?

Check for voltage on the purple and black wires that come off of the board. Should have @ 18 volts dc.

Are you talking about these wires? I am getting 3.2 and 3.3 bolts on the purple wires circled.

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No the purple wire that come from Inkochnito's bridge rectifier board.

Which coil test number is it for the 7 back flashers?
Coil test 7 flashes the one Infront of the left ramp but none of the back ones above the playfield will flash on any of the tests

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You were 100% correct. I had another bridge board and that fixed it right away. I need to contact Inkochnito and let him know this nord failed. I bet I can get replacement rectifiers.

Ty very much!

Did you check the fuses on the board?

Which of those flashers are 28 volt? Is it the 4 near the eject holes only?

I checked them for continuity but nothing else. I’ll get an ohm meter on them.

Did you remove them before checking?

I removed them both. They both pass continuity and show 0 ohms on my meter.

Most likely the bridge rectifier went bad. It can be fixed tho.

Grumpy = The Man.

Following this repair and the one in space station thread.

Yep!! You rock. I just watched this video and sure enough the failing rectifier shows a value across the AC posts.

Now if only I can figure out where to buy these.

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https://www.greatplainselectronics.com/proddetail.asp?prod=GBPC3504W

Even your google skills outmatch mine . Thanks again!

Playball!

This is crazy, but the new bridge board is starting to fail now too. Something must be causing this. Any ideas?

Bad batch of rectifiers?

Certainly not impossible, but these were purchased at different times from different vendors. Is it possible for anything upstream to be blowing it?

This rectifier is good for 35 amps with the proper heat sink. It's fused at 8 amps. You should blow the fuse before any damage has occurred. Even if all the lamps in the lamp matrix were to be on at the same time it would only draw 16 amps. If you had a dead short, that may cause damage to the bridge. But if you have a short the lamps wouldn't come on at all.

Also I have full LED so the amp draw should be less. I need to get back over to the bar, maybe the second board just had a crap fuse…but I still think that is suspect. I am really confused by this one.

I replaced all of the caps on the power source. Works great. Thanks!

Ok, just got over to the bar…same issue with this bridge board. Same exact rectifier on this bridge board. The only thing that seems weird to me is the circled resistor on the power board was covered with a white powder. Idk how those broke resistors pop. Any more thoughts?

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That is a "fire" resistor. They get hot and are packed in that little ceramic box for that reason. I doubt it failed. They are pretty tough plus super easy to test. Find out what the value should be from the schematic and test with your multi meter. My guess is that it is fine.

Ok, I should have tested it. I forgot to do that while I was there. Good to know that they probably don’t fail. Nothing else on the board looked visibly off.

If that resistor went bad the game won't work at all. Crazy that 2 bridge rectifiers went bad like this.

GRUMPY you are going to love this…I got the new rectifiers today. I tested one, and everything looked great, so I removed the bad one and soldered on the new one. Once it was soldered in I tested it again. That time it failed. I was like WTF, so I tested the “bad” one I removed. Guest what? That one now tests correctly.

I can’t figure out how that would happen. Either the boards are somehow bad or the tests I am performing are incorrect. This is starting to get crazy.

Hello Aniraf,

Well, that's odd.
This would be the first to fail in 750 Bridge Boards.

You say the rectifier for the 18V fails.
Which diode of the rectifier fails?
From AC to minus or AC to plus?

I've looked a bit closer to the Bridge Board....
Would it be possible that there is a short between the fuse clip and the ground trace?
A solder splatter????

Kind regards,
Peter
www.inkochnito.nl

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Remove the rectifier again and test the traces.
I think there is a short somewhere....

Why don't you check the 2 connectors for the 18 volt side of the board. Make sure that you didn't clamp down on part of the insulation of the wire. This could cause a intermittent connection.

Ok, let me detail the test a little more. I have two bridge boards. GRUMPY suggested that the 18V rectifier failed, so I tested for 18V, didn’t see it, and swapped the bridge board. All of the lights started working again.

One day later, all of the lights went out. So I started testing the rectifiers directly. On both bridge boards, the 18V rectifier shows a continuously climbing value of 1.7 on my diode test for the AC to AC poles of the 18V rectifier.

The 34V side and the new rectifiers I bought do not show any value for AC to AC poles. In fact, the rectifier I removed (which was “failing”) now does not show a value for those poles.

On the newly soldered rectifier I also see a value around 1.4 to 1.8 when I test positive to AC or negative to AC. According to the video above, I should see something around .457 which is exactly what I see on the 34V rectifier and the one I removed.

I am doing all of my testing on a bench with no power running through the board. The bridge board appears to be in perfect condition with no solder splatter, dust or broken traces.

Thank you very much @inkochnito. I am sure there is something I am doing wrong as these are great products!

Is it normal for the game to fire the knocker several times when announcing problems (“check switch xyz” etc.) at boot?

This is caused by the 2 caps on the 18 volt bridge, there are no caps for the 34 volt bridge.

You should also look at the molex connector in the lower cabinet near the transformer for a pin that is not fully seated in the connector.

Yes.

So you are saying that the behavior is expected?

I’m going to head over there this evening and I’ll go digging. I don’t know that it would explain the switching to a new board fixing it.

The switching of the connectors may have fixed it for awhile. Look carefully to make sure you didn't clamp down on the insulation of the wires.

Ok, updating on the rectifier saga:

I went to the bar and took @grumpy’s advice and made sure to strip back all of the shielding on the 18v line and ground. Once I was certain that was clear I tested it again…no dice.

I noticed the the little green ground LED for the 18v side wasn’t lit, so I started poking around at the power board where the two grounds come from. No matter what I did I couldn’t get it working.

I decided to swap the bridge board with the one where I soldered the new rectifier. As soon as I flipped the switch, everything came alive!

We shall see how long it lasts. Hopefully I just ended up with blown rectifiers…but that seems way too odd for two totally different boards to have blown them. Inkochnito has awesome boards and there are no signs of any issues. I am still confused by what I am seeing.

Shit Happens!

Scratch my last post, it failed again. F!

Any ideas?

Did you do the AC input side too?

I think I only checked the output side. That said, switching the board shouldn’t have fixed it. It ran for almost a year prior. If the shield was not cut right, wouldn’t I have seen this earlier?

Anytime you move a intermittent connection it may start working again.

Do you have an image of the installed board?
Just to make sure all wires are in their right place....

When the board fails, do you have input power (14Vac)?

Not the best picture, but if you zoom in you can probably see it. Keep in mind that this has been running in this configuration for roughly a year. I am fairly certain that everything is corrected correctly. Most likely something is shorting out, or starting to fail.

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I went over tonight and adjusted it. I am thinking GRUMPY is correct and that it might actually be the shielding on the wires. I trimmed it back more and it seems to be working now. I’ll keep everyone posted.

GRUMPY and Inkochnito I am going to close this out and say that GRUMPY was right. It was bad contact being caused by the shielding. Thank you for all the help!