Re: Hello from newcomer Fabio Trevisan - My first Tek Scope 464 + DM44


On Tue, 4 Oct 2016 12:33:48 -0300, you wrote:

The HV transformer... between the HV winding (Cathode & PDA supply) and the
600V bias winding...
Cold, it already measures 10~15uA under 3kV (A WARNING SIGN)
Hot...enter the Drum Roll... 400uA!!! and my test HV supply sags to 1500V!
It didn't take all the heating above to present the increased leakage...
Leakage skyrocketed after about 40 deg celsius.

So... I think I (we) have a culprit!!!
At 400uA, this leakage alone is taking up 200% of the current actually
drawn by the HV circuit under normal operation.
That is a bummer. I try to rule out everything else which is what you
did before getting to the more difficult to test and replace

Usually the transformers fail in a more definitive way.

P.S. I didn't have to resort to my Kenwood's HV supply...
I found a broken mosquito zapper (HV racket) hanging around (the racket was
bent and shorting).
It delivers about 3200V from 2 x AA batteries and it's safe (not connected
to mains and low power)
That is a great idea.

So I think now I`ll have to order one transformer from
I see that Sphere has NOS (new old stock) 120-0909-01 transformers in
stock. I checked QService and they do not have any.

The $65 price from Sphere for the transformer is greater than some
past 464 and 466 sales on Ebay.

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