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

John wrote:

How do you check a bridge rectifier in circuit to be absolutely sure it
needs replacing.

What makes you so sure that's even possible?

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




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John wrote:

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


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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"John" wrote in message
net.ca...

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.

Desolder the output leads of the transformer and check again.

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John wrote:
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




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

James Sweet wrote:

John wrote:

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



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

That's not "in circuit."

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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.

"John" wrote in message
net.ca...
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

John wrote:
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

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.

Thanks for all your replies. Will proceed as advised .
"CJT" wrote in message
...
John wrote:

How do you check a bridge rectifier in circuit to be absolutely sure it
needs replacing.

What makes you so sure that's even possible?

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


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