DKE 38 restoration

[bandersen]

There is filament continuity on both original tubes so fingers crossed they are still good. I really don't want to use that wacky Russian sub if I don't have to.

Right away I discovered one problem. The antenna coupling control is broken. A little glue took care of that.

Everything in this radio is very simple and fragile to keep costs down. I'm being very careful not to do any damage as I work.


I tested the restuffed electrolytic caps and they appear to have 10uF caps good to 450 volts in them. Even so I'm wary to leave them in no know what really in there.
Instead I installed two poly film 4.7uF caps rated for 450 volts. I'll keep the old caps in case someone wants to reinstall them someday.

The rest of the work done seems sound. A couple mica caps were doubled up and resistors put in series for oddball values, but it all looks OK. Fuse is good too.

So I hooked it up to a variac set to 110 volts and fired it up. Nothing, nada. No power is getting through the radio.

Eventually, I noticed that the funky power switch wasn't working. It's made from some brass strips, and a spring loaded phenolic arm with metal ball contacts.
The idea is that in the "ON" position the balls will complete the circuit through the brass contacts.

Well, one of the contacts is twisted out of position. (Sorry for the blurry photo).
I got it back in position and cleaned the contacts, but it's still not making reliable contact so I bypassed it for now with jumper wires.

Still nothing


More trouble shooting finally led to the fuse holder. The fuse is good, but it wasn't making solid contact with the holder. After cleaning that up, I've got glowing filaments.
A short while later, sound

After attaching an antenna, I was able to receive several local AM stations. Not the greatest volume and it takes some careful control manipulation to tune them in.
A little off and the volume drops or it brakes into oscillation and howls.

A funky radio to operate but very interesting piece of history. I'll tidy up my work and add a thermistor to protect the tube filaments.

[Findm-Keepm]

Originally Posted by bandersen

Everything in this radio is very simple and fragile....

And odd.