Tube experts! - I need your assistance.

From: Dave Dameron <ddameron_at_earthlink.net>
Date: Sat Dec 4 00:54:38 1999

Hi John and all,
At 10:42 PM 12/3/99 -0500, you wrote:

>This scope uses a primary transformer to supply the 6.3V to most of the
>tubes and has a separate winding for 6.3V for the CRT heater. Off this
>transformer another winding fed to a voltage doubler and then to an
>oscillator with another transformer to create a wide range of voltages. (12V
>to -3000).
>
>Picture this... the -3000 volts is fed right into the CRT heater (which
>happens to be directly coupled with the primary transformer). I have been
>able to locate the problem somewhat. If I remove the -3000 volt line between
>the HV rectifier tube and the CRT itself then the scope works fine! All
>waveforms are proper and the power supply works great (no picture of
>course).

Is the -3000 volts there when not connected to the CRT heater (and are you
equipped to measure that)? If so, your #2 is probably correct.
>
>It can be a few things... I am hoping someone here who use to work on tube
>units might be able to tell me which problem below it most likely is:

>#2) Bad insulation on the primary transformer secondary "crt heater" winding
>which jumps over to the other winding that happens to be the main
>powersupply winding (125V X 2)
>
-Dave
Received on Sat Dec 04 1999 - 00:54:38 GMT