(Topic ID: 238098)

Bally as-2518-54 rectifier board question


By Calipindave

1 year ago



Topic Stats

  • 10 posts
  • 3 Pinsiders participating
  • Latest reply 1 year ago by Calipindave
  • Topic is favorited by 2 Pinsiders

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#1 1 year ago

Hey guys. I am working on the rectifier board in my EBD.

I have the repair kit from Big Baddy and have replaced the fuse clips, ceramic resistors, two burned out fuse clips, and the four big diodes.

A couple of questions:

1) the small diodes and resistor all look good. Should I bother with replacing them.

2) br1 was missing on the board. Br2 looks good. It looks like there is a pad of some kind mounted under br2 between it and the board. I assume it’s a spacer so br2 will touch the metal plate.

I’m at a bit of a loss on what do do with the rectifiers. The replacement ones are smaller and come with one heat sink for br1. How do I mount br1 and its heat sink. They originally install from underneath but I can’t see how they it will fit under the board with a heat sink. If I mount from the top the offset legs don’t match and you are changing where the leads go? I might just leave br2. If I replace it do I have to mount it off the board far enough so it contacts the metal plate to act as a heat sink.

Perhaps if anyone has a picture of how you did your board it would be helpful.

Sometimes the small simple things stop you and make you go hmmmm..

Thanks

Dave

#2 1 year ago

I just did the two rectifiers on a Xenon. I used KBPC3504W rectifiers which have the same dimensions as the old rectifiers. I reused the spacers and mounted them the same as the old. I'm not sure what you'd do if you're missing a spacer. The two rectifiers should be exactly coplanar with the transformer chassis.

I don't know why you'd need a heat sink unless your new rectifiers are intended to go on the component side of the board.

#3 1 year ago
Quoted from Calipindave:

1) the small diodes and resistor all look good. Should I bother with replacing them.

Test the diodes first before deciding. The resistor just goes to test point TP2 so just sits in an open circuit. Replacing it is purely a cosmetic thing.

Quoted from Calipindave:

2) br1 was missing on the board. Br2 looks good. It looks like there is a pad of some kind mounted under br2 between it and the board. I assume it’s a spacer so br2 will touch the metal plate.

I always mount the bridge back in its original position underneath the PCB. Heat dispersion of a small aluminum heatsink is no match for that large base metal plate. The spacer pad you're missing is a piece of bakelite (I think it's 1/16" thick?)

If you're going to install LEDs throughout in the controlled feature lamps it's less critical since there's less current being drawn so the bridge won't dissipate as much power.

Quoted from Calipindave:

If I mount from the top the offset legs don’t match and you are changing where the leads go?

Yes, the positive lead of the bridge is offset so you can't mount it flush on the topside of the PCB. You have to stand it on its legs a bit and bend the positive lead to fit in its hole. You only need to match the positive and negative leads of the bridge to the original PCB positions. The AC legs on the bridge don't matter.

Quoted from Calipindave:

I might just leave br2

BR2 rarely fails. Since it's hard to remove, I'd just leave it too.

#4 1 year ago

Thanks for the advice guys.

I tested R3 and it measures 98.6k ohms which is in spec for the 100k. The diodes measured fine also.

I left br2 as is. With br1 I spaced it out temporarily to give it the right distance from the board and soldered it in. It will sit flush with the plate coplanor with br2.

Question. I have been working ems forever and am doing ok with the ss schematics and the like but then things come along and puzzle me. I always use the mm to check my work, mostly to ensure continuity as a cross check of the solder work and the check for shorts.

Schematics tell me br1 + leg goes to tp1 then on to three connectors on j3 and j1. Between the minus and + legs is the 25ohm ceramic resistor r2.

Continuity (beep) test says I’m good between + leg and tp1 j3 and j1 and it shows almost no resistance. . That aligns with the schematic. Same for + leg and one legs of the resistor. To the other leg of the resistor goes to ground i read 24.9ohms. These all beep out indicating continuity and that’s what I don’t get. With the mm set to ohms I read 24.9 ohms.

By this reading I am being told that I have continuity from the + leg to ground (through the resistor?). Is that right. Is that because with the beep test the 25ohms reads too low and is seen as continuous. I wouldn’t expect to see the + leg shorted to ground (with 25 ohms of resistance only).

I do see with br2 the wiring is the same but don’t get the same beep continuity. That one goes through 600 ohms though and I get a reading of 598 ohms.

Does this seem normal. I just want to make sure that something isn’t shorted that shouldn’t be.

Thanks

Dave

#5 1 year ago

Sounds okay to me. I don't know that there's any "official" definition of continuity. Sounds like the threshold for your particular meter is somewhere between 25 and 600 ohms. Don't forget to add some heat sink grease between the rectifiers and the transformer chassis.

#6 1 year ago
Quoted from JeffZee:

Sounds okay to me. I don't know that there's any "official" definition of continuity. Sounds like the threshold for your particular meter is somewhere between 25 and 600 ohms. Don't forget to add some heat sink grease between the rectifiers and the transformer chassis.

Thanks Jeff. Since I don’t truly understand electrical engineering I see 25ohms as a short because the meter beeps . Like you said those are probably thresholds in the meter. It’s nothing special but a decent fluke.

I have a small amount of grease that came with the rectifier. I hope it’s enough for both.

Dave

#7 1 year ago
Quoted from Calipindave:

With br1 I spaced it out temporarily to give it the right distance from the board and soldered it in. It will sit flush with the plate coplanor with br2.

Find something appropriate to fill in the space, otherwise over time the PCB will end up warping at the screw and the bridge may not sit tight against the metal base plate.

The ceramic resistors across the bridges will give you invalid bridge diode readings on your meter. You can temporarily unsolder one leg of each resistor and pull the leg out of the board allowing you to test the bridges with your meter. Use diode mode on the multi-meter to test the bridges.
Otherwise when you're done, put the rectifier board in the machine and hook up the transformer to it but leave the playfield (J1), cabinet (J2) and backbox (J3 and J4) disconnected. Power up and measure the test points on the rectifier board - use the GND test point on the rectifier board as your ground reference. If any voltages read half what they should you likely have a bad rectifier (open circuit internal diode).

#8 1 year ago
Quoted from Quench:

Find something appropriate to fill in the space, otherwise over time the PCB will end up warping at the screw and the bridge may not sit tight against the metal base plate.
The ceramic resistors across the bridges will give you invalid bridge diode readings on your meter. You can temporarily unsolder one leg of each resistor and pull the leg out of the board allowing you to test the bridges with your meter. Use diode mode on the multi-meter to test the bridges.
Otherwise when you're done, put the rectifier board in the machine and hook up the transformer to it but leave the playfield (J1), cabinet (J2) and backbox (J3 and J4) disconnected. Power up and measure the test points on the rectifier board - use the GND test point on the rectifier board as your ground reference. If any voltages read half what they should you likely have a bad rectifier (open circuit internal diode).

Thank you for the excellent info Quench.

I have a couple of pieces of the brown bakelite? board from an old em machine Will that do?

Dave

#9 1 year ago
Quoted from Calipindave:

I have a couple of pieces of the brown bakelite? board from an old em machine Will that do?

Yes will probably be fine if you have the right thickness.

Clean up any old gummed/dirty thermal paste and apply new as JeffZee mentioned. The bridges must sit perfectly flush on the base plate.

I solder the bridge as the last step - i.e. mount everything back on the base plate and screw the rectifier board down, then solder the bridge legs so finally there's no mechanical stress on the solder joints.

#10 1 year ago
Quoted from Quench:

Yes will probably be fine if you have the right thickness.
Clean up any old gummed/dirty thermal paste and apply new as JeffZee mentioned. The bridges must sit perfectly flush on the base plate.
I solder the bridge as the last step - i.e. mount everything back on the base plate and screw the rectifier board down, then solder the bridge legs so finally there's no mechanical stress on the solder joints.

Thanks Quench.

I will follow your advice.

Dave

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