(Topic ID: 293438)

Should I worry about this bridge rectifier?

By Tomass

5 months ago

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  • 25 posts
  • 10 Pinsiders participating
  • Latest reply 5 months ago by xsvtoys
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#12 5 months ago

Yes ^^ -- the solder looks to be original (there is no flaking of the solder mask near terminals). Is it causing problems? If not, why replace it? If worried about the heat, you can add a heat sink to the bridge rectifier without pulling him off the board.

I'd be more worried about those radial caps getting old and leaking corrosive guts on the board than that bridge.

#15 5 months ago

OK -- do you have +12V and -12V coming out of the bridge?
You didn't state which game so I am assuming a System 7. +12V can be found at test point 3 and -12V can be found at test point 4 (meter ground at test point 2).
If original caps, I would examine caps at C7 and C8 for leakage. Either of those two going bad can kill power the the 5V regulator circuit. See if you can measure a doubled voltage at the cathode (banded end) of diode D1. D1 is above the relay. If not doubled, replace C7 and C8.

While you're there, take a look at C12 and make sure he isn't leaking.

#23 5 months ago
Quoted from Schwaggs:

That is a 35 amp rectifier handling only 7 amps. I doubt it even gets warm.

OK - curiosity got me.

KBPC35 series = 1.1V forward voltage drop per diode.
Two diodes always operating simultaneously.
Power = (2)(1.1V)(7A) = 15.4W
Defined thermal resistance = 1.4C/W
Temperature rise = (15.4W)(1.4C/W) = 21.56C temp rise. (rounded to 21.6)
Ambient = 25C typical so operating temp will be about (25 + 21.6) = 46.6C or 115F. Yeah, it will see a temperature rise but far from being too hot.

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