Is this bridge rectifier shot?

stevenp61

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Testing the BR1 on a DE PPB-1 board.

Black lead on + or red on -, other lead to AC terminals: reading is .45-.5 V

Black lead on - or red on +, other lead to AC terminals: reading is .7-.75 V

Also measuring + to - is right about 0.4 V either way.

All measurements on a pulled board, on the DMM diode setting.

Is this BR shot? Doesn't seem to be open in any direction.
 
Testing the BR1 on a DE PPB-1 board.

Black lead on + or red on -, other lead to AC terminals: reading is .45-.5 V

Black lead on - or red on +, other lead to AC terminals: reading is .7-.75 V

Also measuring + to - is right about 0.4 V either way.

All measurements on a pulled board, on the DMM diode setting.

Is this BR shot? Doesn't seem to be open in any direction.

Nobody? :(
 
do you have to desolder a BR to test it? i would have thought so, since it's just diodes, and if you don't disconnect a diode from the circuit, you can read an alternate path through the circuit. but i don't know for sure.

if not, your BR is bad, as it's not open anywhere (voltage is flowing both directions across all the diodes) - you've short-circuited the diodes.
 
Dokert had a great tutorial on testing bridge rectifiers in the repair forum. My search-fu is particularly weak today and I can't find it. You might want to search for it or drop Dokert a note and see if he saved a link to it.

ken
 
This should help you out.


OK, that helped. Thx! I was under the impression that you also had to test 'backwards' (+ lead to + terminal, etc.) Happy to report that the 4 readings (2 from + on - and 2 from - on +) all were between 400-600. :)
 
Can anyone explain the significance of the 400-600 range on the meter? Does this indicate how much of a voltage drop the diodes produce? How can you figure that out?
 
Thanks Dave. It's easier to point people at your tutorial than it is to try and explain it. Good job!

ken

Yup. I'm not generally a fan of videos (preferring text-based info) but this was short, clear, and helpful! Thx guys.
 
Can anyone explain the significance of the 400-600 range on the meter? Does this indicate how much of a voltage drop the diodes produce? How can you figure that out?

400-600 is the voltage drop, in mV (or in Volts if there's a decimal in there, such as 0.400 - 0.600V) across the forward-biased diode, at some semi-arbitrary test current the meter provides.

Note that a diode doesn't "produce" any voltage, per se. The EMF is provided by the meter, the resulting voltage drop across the diode occurs and is measured.

Not sure what you mean by "How can you figure that out?"
 
400-600 is the voltage drop, in mV (or in Volts if there's a decimal in there, such as 0.400 - 0.600V) across the forward-biased diode, at some semi-arbitrary test current the meter provides.

Note that a diode doesn't "produce" any voltage, per se. The EMF is provided by the meter, the resulting voltage drop across the diode occurs and is measured.

Not sure what you mean by "How can you figure that out?"

So the meter puts out x volts and then measures it on the other side and displays what the voltage drop is?
 
So the meter puts out x volts and then measures it on the other side and displays what the voltage drop is?

Kinda. I think they're actually current-driven; so it automatically adjustes it's voltage output to whatever it takes (up to a few volts) to generate so-many milliamps of current thru the test device... and displays that voltage.
 
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