(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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#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.

#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).

#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.

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