3 Dec
1999
3 Dec
'99
4:54 p.m.
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