29-11-2020, 12:34 PM
A word of warning using old valve holders.....
Having sorted out the detector stage I found that the RF stage was dead.
HT on valve OK but not drawing any current.
Then I noticed that the valve was not getting slightly warm as it should,
in drawing 6,3v at .3 amps, nearly 2 watts.
Checked heater volts at pin connections. All OK.
Took out valve and checked for 6.3v at valve holder. All OK !
I'm sure the ghost of the first one I built 70 years ago was playing tricks again.
Then I tumbled to it. I was using old valve holders from way back and
there was slight oxidation right inside the valve pin connections in the valve holder.
A tiny scrape inside the two heater connectors and set sprung to life.
Beware using old valve bases. The ghosts of past circuitry will get you !
Having sorted out the detector stage I found that the RF stage was dead.
HT on valve OK but not drawing any current.
Then I noticed that the valve was not getting slightly warm as it should,
in drawing 6,3v at .3 amps, nearly 2 watts.
Checked heater volts at pin connections. All OK.
Took out valve and checked for 6.3v at valve holder. All OK !
I'm sure the ghost of the first one I built 70 years ago was playing tricks again.
Then I tumbled to it. I was using old valve holders from way back and
there was slight oxidation right inside the valve pin connections in the valve holder.
A tiny scrape inside the two heater connectors and set sprung to life.
Beware using old valve bases. The ghosts of past circuitry will get you !
