Re: Tek 576 Curve Tracer HV Replacement Transformer


Mlynch001
 

On Tue, Apr 7, 2020 at 09:34 PM, Ernesto wrote:


Michael, Chuck,

Why is a resistor in series with the multiplying ladder necessary? Isn't the
internal helical coating of the CRT a load and a drainage means of the ladder
capacitors?
In the 547 there is a 1 Mohm 1/4 watt resistor after the ladder, followed by a
500pF capacitor to ground.
In the 7704A there is no visible resistor, and the do-it-yourself circuit does
not show one inside the X14 module.

Ernesto
Ernesto,

I do not know the answer to that question. Chuck indicates that it to prevent being killed by a high current- high voltage from an accidental shock. What I do know is that the Tektronix specifications for the 152-0552-00 call for a series resistance of 510k ohms. This is found in the TEKTRONIX Cross Reference manual. The pictures of a DIY multiplier by member Marcus PP5MS can be seen in a series of pictures at this link:

https://groups.io/g/TekScopes/album?id=13113

Marcus - PP5MS 465-475 HV multiplier

His version clearly shows a resistor in series. His looks like 47K Ohm to me. His x ray also shows something in the Anode wire that could be a resistor.

I do not know all the technical reasons for this. But the specification is there, so there must be a good reason for this resistance.

I will defer to the sharper members to explain it to me.

If I build one of these, I want to match the original as closely as possible.

--
Michael Lynch
Dardanelle, AR

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