Re: Tek 576 Curve Tracer HV Replacement Transformer

Chuck Harris

The resistor is there to protect the tripler if the anode
lead is suddenly shorted to ground. It will drag the capacitors
to ground without allowing the current to get high enough to
damage anything... in theory.

However, if the capacitor simply blows up due to the surge
of high voltage/current across the resistor, how does it matter
that the diodes are still good, but the resistor is shattered
into an open circuit condition?

In the 547, that resistor is a 10M 1/4 watt carbon composition
resistor. But the capacitors in the 547 are quite a bit larger
than I believe the 465's tripler's uses.

In the 547's case, I think they were trying to protect the
wayward technician that gets across the live HV. It could
cause a heart arrhythmia in a properly connected person.

-Chuck Harris

Mlynch001 wrote:

On Tue, Apr 7, 2020 at 06:42 PM, Chuck Harris wrote:

I don't have a schematic of the tripler, so I don't know where this
resistor is located.

I suspect that it is in series with the anode lead. That is often done
for safety reasons. They don't want a full discharge of the tripler's
capacitors to stop your heart...

It was probably a carbon composition resistor, and probably 1/4 watt.

-Chuck Harris

Mlynch001 wrote:
I do have a question about the load resistor. I think it is supposed to be
about 470K Ohms? Does this need to be a special resistor or can you use a
1/2W metal film resistor?

There are some pictures in the TEKScope archive. One of our members posted a lot of pictures, including X-Ray pictures of the internal structures. They show the resistor soldered between the last diode in the chain and the end of the anode wire. I don’t have any carbon comp resistors of that resistance rating, but tons of 1/4W metal film and carbon film resistors. Would either those types be acceptable for this application? I can probably find some carbon comp resistors if absolutely necessary.

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