Civilian Wartime Receiver

[Sparks]

The power supply is now wired up and working.    I put a neon lamp permanently  across the smoothing capacitor to let me know if the set is switched on when working underneath it.    I really think such a warning device should have been fitted to all valve radios, as a lot of shocks were received because  "I didn't think it was switched on!"
Bob  
   

[Sparks]

Here are all the discarded components.    I don't think I have ever seen a receiver in such a mess!
Bob
   

[Sparks]

Vi frequency changer wired up. Oscillator tested OK with frequency counter - things looking good - Bob

[Murphyv310]

You didn't chuck out the westector did you?

[Sparks]

No, I didn't chuck anything out, it is still lying there amidst all the junk. I did test it with the meter, but didn't really know what to expect, it certainly didn't behave like a germanium diode as far as resistances were concerned.
Bob

[Murphyv310]

Hi Bob.
No it reads totally different to a germanium diode. I remember having another utility set to fix with a duff diode, it did work but would only work on the strongest of signals and then only with distortion. A germanium diode doesn't work properly in this set as the circuitry is designed for the copper oxide diode which has a high forward impedance. The old TV M1 diode works well, it's possible a silicon diode may work too. I would imagine that if you modified the forward bias the diode needs in this set a germanium diode could work..... something though I have not tried.

[Sparks]

Trevor,
When I first got the set to work before the restoration, I replaced the Westector with a germanium diode and it worked fine!   With all that rotten wiring, I didn't feel that it was safe, and it looked pretty awful as well, which is why I decided on a complete re-build. You can see the Westector in the pile of junk in #12 above!    
Bob

[Murphyv310]

Hi Bob.
Oh well you had better success with the Ge diode than myself then. I suppose it may be to do with the biassing arrangement for the old diode. If the cathode volts were low or even the 6V6 down a bit a Ge diode would most likely work OK. I may pull my set out of the Museum and have a play about with diodes and see what works the best with differing bias arrangements.

[Alistair D]

The power supply is now wired up and working.    I put a neon lamp permanently  across the smoothing capacitor to let me know if the set is switched on when working underneath it.    I really think such a warning device should have been fitted to all valve radios, as a lot of shocks were received because  "I didn't think it was switched on!"
Bob  

One of my Tek scopes has a similar arrangement. The main difference is that the Tek actually has a capacitor across the neon forming a relaxation oscillator. The eye is even more quickly drawn to the flashing neon. 

Al

[ppppenguin]

.... I put a neon lamp permanently  across the smoothing capacitor to let me know if the set is switched on when working underneath it.    I really think such a warning device should have been fitted to all valve radios, as a lot of shocks were received because  "I didn't think it was switched on!"

The accountants would never have allowed the extra pennies on the cost.