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Bridge rectifier.

How do you check a bridge rectifier in circuit to be absolutely sure it needs replacing. Conditions: No power applied as 2amp fuse in the transformer primary blows immediately power is applied. Usual short circuit procedures followed throughout but I don't place too much reliance on this test . BTW, the rectifier (B40 C3200/2200)) is in a theatre organ purchased from an outfit no longer in business and space on the pcb is at a premium and discourages using single diodes. Thanks - John

Reply to
John
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What makes you so sure that's even possible?

Conditions: No power applied as 2amp fuse in the

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Reply to
CJT

the primary side of the xformer could be shorted.

to check the rectifier. put your DMM on ohms, place the red lead on the

  • output of the rectifier and black on the -. if you have a very low ohm reading, you have either a rectifier or a capacitor or something else connected to the supply shorted. normally, a fuse won't blow instantly unless it's shorted on the primary side. have you checked for any shorted MOV's ?

the only way to know this, is to disconnect one side of the secondary and put in another fuse, then fire it up. if you don't want to use fuses, use a lamp of a set wattage that is near the fuse rating inplace of the fuse. if the circuit is still shorted badly, the light will glow and produce low current in your circuit..

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Reply to
Jamie

Desolder the output leads of the transformer and check again.

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Reply to
Homer J Simpson

Remove it from the board and check the individual diodes with an ohm meter, they're all accessible from the pins.

Reply to
James Sweet

That's not "in circuit."

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Reply to
CJT

have you ever checked power diodes that thay check ok but still not work. ive had that also with transistors as well. thay can check out ok but can have probs when power applied.

circuit

purchased

Reply to
zack

On Sun, 29 Oct 2006 20:34:00 -0500, John Has Frothed:

Take the thing out and check it. You do know how to check a diode do you?

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Reply to
Meat Plow

First measure across the + and - leads of the bridge. If it's a steady LOW, like under 10 ohms, then it could be the bridge or anything after that. You'll have to cut the + lead of the bridge to isolate the problem any further.

Then use an ohmmeter on its low ohm or "diode" range and measure the resistance across each diode, in both directions. It should be very different each way for each diode.

That part is a 4-amp 100 volt bridge. The rating may have been marginal so I'd replace it with a somewhat heftier bridge.

Reply to
Ancient_Hacker

Reply to
John

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