Kenneth Grimm wrote:
I've got a set of four epoxy block diodes that I would like to use in
my next home brew amplifier power supply. The problem is that the
company that made them, CSdc (Conditioning Semiconductor Devices
Corporation) was bought up back in the 80's and I can't find anything
on the web about the value of the devices. I would sure like to know
what C67-6225A by CSdc is. They are 1 inch square by 5.5 inches long
black epoxy blocks. Any help would be greatly appreciated.
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Your expoxy embedded diode block is highly likely containing some 1000 V
PIV silicon diodes wired in series.
Suggest ,with a low voltage power supply, you allow 20 - 30 mA
(forward bias) current to flow through the block.
With the knowledge that the voltage across each silicon diode is approx
0.7 V you measure the voltage across the block ,and then can
determine the number of diodes and hence the overall PIV. The max AC
rms voltage to be rectified should be less than 35 percent of that
PIV, being 70 percent of half the PIV

The max current the block can accept can be ESTIMATED in 2 ways.
Allow a DC current to to flow such that after a while the block is
'hand warm' , alternatively the current at which the voltage across
the block has increased by 30 percent compared with the voltage across
the block at a current of 20 -30 mA


I agree the above methods do not constitute a very scientific approach
,yet they provide useful info for practical purposes.

I have done the same with some 'mystery' HV diodes and so far ....so good.

Suggest you test/verify the above method(s) with a HV diode from a
microwave oven with a known capacity .If not known ,the HV voltage of
the relevant transformer can be calculated (if not measured directly )
by connecting the primary winding to a low voltage ( 10 -15 V) and
measuring the voltage across the secondary.

Frank GM0CSZ / KN6WH