Electronics > Repair

Tektronix SC504 HV multiplier

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I had done LT spice sims and the configuration with C3 connecting to top of C1, instead of GND, does not actually work as a tripler...
We know the AC input goes not to one capacitor (i.e. Cockroft Walton), but to a diode and capacitor. The only part not 100% on was the 1.5MEG arc limiter, not that it could really take it unless larger carbon-comp. It's just to protect the diodes. Cockroft Walton also has 1/2 wave ripple when using an odd number of stages.

On that schematic I drew, my sims show:
C1 sees Vpk
C2 sees 2*Vpk
C3 sees 3* Vpk

I am in the process of making one for my CS 502 (uses the same multiplier as the SC 504), and would just like to hear from you who have made one, how it works over time??

I use 2000pF /15KV capacitors instead of 2200pF as I couldn't find any that had 2200pF / 15KV in stock, and I also use a 1.5Mohm 12 KV HV resistor.
What do you think??

In advance thank you

Doug Brewster:
Hi x-tian

I only have three of the of the SC504 instruments now having sold the remaining four some years ago. The three I still have are working well; I think two of them have the home made multipliers. The 2000pF capacitors I think will be OK - a lttle more ripple perhaps. For the 1.5Meg resistor I think I used standard metal film resistors.

Many thanks Doug Brewster.
It was a fantastic job you did in terms of getting the old Tektronix module oscilloscopes working again, despite the discontinued parts.

I've just cast epoxy in the box with fresh components, so we'll have to see if my version works when the epoxy has hardened.

I will write an update when the result is available.

It's Alive


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