Work on the 6F6 with dull glow first. Fixing this may make the other problem go away? This tube will operate hot but plate shouldn't glow.
Pin #5 must be around 20 volts negative when measured from pin #8. If not, the tube will draw too much current, distort and damage other components. Coupling cap to pin #5 must not have leakage. Grid resistor on this pin needs to be .5 meg or less.
Norm
:Hi
:I have a Philco 37-630 that plays fine until you try to raise the volume above medium level. Then it begins to make a repetitive whooshing sound and the normal audio disappears. Once it starts doing this I have to turn it off and wait for a while before I can get normal audio back, at a lower level of course. The problem seems to be downstream of the volume control so I have changed all the paper caps from that point forward. I have tried different 2nd detector and output tubes. I have tried a different speaker/field coil/audio transformer and it does the same thing. I do notice that the 6F6GT seems to run hot, it has a dull glow.
:I remember reading somewhere that tube sockets can develop conductive paths between pins that act erratically but I haven't pursued this.
:Any ideas would be greatly appreciated.
:Thanks in advance
:Jim
Thanks. I have checked the bias voltage and the coupling capacitor and they look OK. I will take a shot at the resistor tonight.
Jim
:Hi Jim
:
: Work on the 6F6 with dull glow first. Fixing this may make the other problem go away? This tube will operate hot but plate shouldn't glow.
:
: Pin #5 must be around 20 volts negative when measured from pin #8. If not, the tube will draw too much current, distort and damage other components. Coupling cap to pin #5 must not have leakage. Grid resistor on this pin needs to be .5 meg or less.
:
:Norm
:
::Hi
::I have a Philco 37-630 that plays fine until you try to raise the volume above medium level. Then it begins to make a repetitive whooshing sound and the normal audio disappears. Once it starts doing this I have to turn it off and wait for a while before I can get normal audio back, at a lower level of course. The problem seems to be downstream of the volume control so I have changed all the paper caps from that point forward. I have tried different 2nd detector and output tubes. I have tried a different speaker/field coil/audio transformer and it does the same thing. I do notice that the 6F6GT seems to run hot, it has a dull glow.
::I remember reading somewhere that tube sockets can develop conductive paths between pins that act erratically but I haven't pursued this.
::Any ideas would be greatly appreciated.
::Thanks in advance
::Jim