Inside the Codar CR 70A Mk II
Seeking a fault!
After quite a long time in storage in my loft, this radio emerged for a period of activity.
However, it was completely dead!
The radio lit up, dial lights and valve filaments on, some slight hum and hiss from the speaker (more when the BFO was on), but not a dicky bird of a radio signal to be heard.
I figured it was a front-end fault, as there wasn't even a crackle as the band switch was operated.
Having spotted some "stressed" (i.e.semi-cooked) resistors around V1, the heptode/triode frequency changer stage (all starting to make sense now ...), I probed around with my test meter and fairly quickly found that V1's cathode resistor (150ohm) was completely open circuit. Not "high resistance", but infinite ohms.
Close inspection showed (sadly I didn't take a photo of this) there was perhaps a crack through the resistor body (I tried wiggling it, but it wouldn't budge).
Anyhow, infinite ohms clearly wasn't correct, so I de-soldered the resistor, which unsurprisingly came out in two parts, and replaced it with a 180ohm 1-watt resistor from my stock.
Hey presto, one fixed radio!
It now works just as badly as it used to! :-)
Inside the Codar CR 70A Mk II
Seeking a fault!
After quite a long time in storage in my loft, this radio emerged for a period of activity.
However, it was completely dead!
The radio lit up, dial lights and valve filaments on, some slight hum and hiss from the speaker (more when the BFO was on), but not a dicky bird of a radio signal to be heard.
I figured it was a front-end fault, as there wasn't even a crackle as the band switch was operated.
Having spotted some "stressed" (i.e.semi-cooked) resistors around V1, the heptode/triode frequency changer stage (all starting to make sense now ...), I probed around with my test meter and fairly quickly found that V1's cathode resistor (150ohm) was completely open circuit. Not "high resistance", but infinite ohms.
Close inspection showed (sadly I didn't take a photo of this) there was perhaps a crack through the resistor body (I tried wiggling it, but it wouldn't budge).
Anyhow, infinite ohms clearly wasn't correct, so I de-soldered the resistor, which unsurprisingly came out in two parts, and replaced it with a 180ohm 1-watt resistor from my stock.
Hey presto, one fixed radio!
It now works just as badly as it used to! :-)