Civilian Wartime Receiver

[Sparks]

This is a wartime civilian radio of standard design.   They were produced in great numbers during WWII, and it is at least 75 years old.     I obtained it from a car boot sale some time ago for £10, and covered a temporary repair of it on here at the time.    After a very long interval, I have now decided  to see if I can get it up to 100% performance again.    The internal wiring is rotten, decayed and unsafe.   It will need an extensive re-build and clean up.   I obtained a circuit diagram from the internet, and I have just been making notes of all the important points to take into consideration for the revival of it.   I also have the original cabinet that is not in too bad of a condition.      It is a three valve superhet, with an ECH35 triode-hexode frequency changer stage, followed by an EF39 pentode IF stage and a 6V6 beam tetrode power amplifier stage.
Bob
       

[Murphyv310]

These are lovely little sets and did the job very well for the masses at the time of conflict.
They are basic with a low component count. The job should be easy and straightforward.
Incidentally they are not hugely sensitive but work well with a good aerial and earth.
Good luck.

[Sparks]

Although I got it working, the wiring was rotten and decayed, and most of the components were extremly dirty and off spec.     It will be a complete re-build, so, after making all sorts of notes and colour coding the IF transformer and coil connections, I ripped the whole lot out!
Bob

[Sparks]

Chassis re-sprayed - Bob

[Crackle]

Hello Bob
I have missed your posts. I bet this radio is going to look good when finished.
Do you have the cabinet and transformer?

Mike

[Sparks]

Hello Mike,
It was complete apart from the power unit and the cabinet is not in bad condition either.     I have an isloation transformer with 240 Vac in and 240 Vac out that fits under the chassis and a small 6.3 Volt trasnformer for the heaters to be mounted above the chassis.     I didn't like the original design of transformer on top and rectifier on top of that as it made it look unbalanced.    The fact that it wont be historically accurate doesn't bother me, because they are common enough.   I just want to see it working and good for another 75 years.    The re-spraying of the variable capacitor called for some careful masking with paper tape, but managed it OK.     I haven't done any radio for months.    I expect somneone will be along shortly to tell me I am doing it wrong!
Bob
   

[Crackle]

Bob your efforts always come out like a work of art, and a joy to look at. I would be very surprised if anyone would be critical.

Mike

[Sparks]

Power supply transformers and smoothing capacitors added.   The isolation transformere for HT is below the chassis, and the heater transformer above it.    The reservoir/smoothing capacitors (in single can) are mouted in a spare valve hole that just happend to be in the chassis.     A silicon diode will take the place of a rectfier valve - Bob
   

[Murphyv310]

Nothing wrong with your work at all. We have to remember that the set could well have been in use for twenty or more years, so if a part failed like the mains transformer then a substitute would have been fitted. My wartime utility set was in regular use up to 2003 when it's owner passed away, it's now on display at my friends museum.

One small point is your isolation tx, a single secondary winding and one diode will be half wave rectification, so smoothing may need to be increased, you could use a bridge rectifier but remember to add in a limiter resistor so the HT is correct when the set is warmed up.

[Sparks]

Thanks,
I hadn't got a bridge rectifier handy, but it can always be changed later. Actually, this set was in such a bad state, it was really only fit for the rubbish tip! That is why I decided on a complete rebuild. Not much of the original was salavgeable although I did get it working before I started. The valves are OK, the IF transformers and coils are OK. Tuning capacitor OK. The case is not too bad, and the loudspeaker and matching transformer are OK. And the chasis, of course. I only sprayed the top, front and back of the chassis. The underneath is bare so I could get the earth connections OK.
Bob