Re: Repairing my Tektronix 454 oscilloscope need some advice

Chuck Harris

Indeed, which is why I said a 9V battery, or two...

The diodes in these supplies are a little special in that
they need to be fast recovery diodes. They are working at
about 50KHz.

A common ordinary microwave oven makes its HV at 60Hz, and
can use very slow recovery diodes effectively. A slow diode
will drag a 50KHz supply down, appearing as a short circuit for
several tens of microseconds after the transformer's polarity

-Chuck Harris

Ernesto wrote:

Hi Chuck,

Some HV diodes may need more than 9V to turn on. The ones I used in my HV supply need about 17V for a 2mA forwards current. they are some Chinese 20KV diodes used in microwaves (an overkill but cheap, at $7.49 for 8 of them at Amazon). He can use the +100V of the scope itself through a 100K resistor for a short measurement of 1mA forwards, then reverse the diode and measure zero current.


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