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 Post subject: Checking BIG solid state rectifiers
PostPosted: Mar Tue 06, 2018 6:44 am 
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Joined: May Wed 25, 2011 5:35 am
Posts: 34
Location: Vancouver, BC
I've fallen heir to a bunch of s-s S5130 rectifiers, large 4 pin base with a plate cap (replacement for 866, 3B28, etc.), but I don't seem to be able to check them, either by 'ringing them out' or with an ohm meter. What am I overlooking?

VE7XF


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 Post subject: Re: Checking BIG solid state rectifiers
PostPosted: Mar Tue 06, 2018 6:58 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 33209
Location: Maryland 20709, USA
Use a high-voltage power supply in the 100-250 volt range.
Add several series resistors large enough to limit current to about 1mA.

Measure the voltage drop across one of the resistors.
Repeat for each plate, forward and reverse polarity.

You should read expected voltage (E=IR) at one polarity, zero voltage for reversed.

- Leigh

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 Post subject: Re: Checking BIG solid state rectifiers
PostPosted: Mar Tue 06, 2018 3:07 pm 
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Joined: Jun Mon 24, 2013 3:00 pm
Posts: 1129
Location: Champaign IL 61822
Use an isolation transformer. Connect the secondary across the diode in series with
a 39K resistor. Connect a scope across the diode, set for DC. On one half-cycle you should see
full line voltage, on the other, the diode voltage drop plus any voltage drop across
a built-in resistor. You can figure out the resistor value from the the voltage across it
versus the corresponding voltage in the same phase across the external resistor.

A better test would use a 1K resistor, but that would have to be a 10W wirewound.

This is not an adequate test for reverse holdoff.

With a dual trace scope the isolation transformer is unnecessary: use both channels
in "subtract" mode, and you can connect direct to the line, neither scope probe grounded at all.


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 Post subject: Re: Checking BIG solid state rectifiers
PostPosted: Mar Tue 06, 2018 5:56 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9385
Location: Santa Rosa, CA
Unfortunately, these are rated for several thousand volts. https://frank.pocnet.net/sheets/049/8/866A.pdf

Any test you do with a low voltage ohm meter is probably meaningless, unless the rectifiers are shorted.

Even testing at a few hundred volts won't tell you if they can sustain kilovolts. If you did measure 1 mA of leakage at a couple of hundred volts, I would say the units are bad. They should be below 100 microamps.

Those rectifiers are likely quite old and built with silicon technology that was in its infancy. Personally, I would not use them.

Rich

PS: any logo on them? These used to be made by Sarkes (ST) or International Rectifier (IR).


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 Post subject: Re: Checking BIG solid state rectifiers
PostPosted: Mar Wed 07, 2018 12:36 am 
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Joined: May Wed 25, 2011 5:35 am
Posts: 34
Location: Vancouver, BC
>Any test you do with a low voltage ohm meter is probably meaningless, unless the rectifiers are shorted.
OK, that's my mistake. I'll drag out a HV supply and try again.

>PS: any logo on them? These used to be made by Sarkes (ST) or International Rectifier (IR).
Yes - most are ST. A pair of SES are half the weight of the ST.

Tnx all for the help.

VE7XF


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