Radionette revisited...and fixed.

I've not had an opportunity to spend time in my workshop for a couple of weeks, but I did find time today to have another look at the Radionette Kurer valve portable.

With the faulty set tuned to 1000 kHz on the medium wave band I was able to pick up a strong 1455 kHz signal on another set next to it on the bench. This confirmed that the Kurer's Local Oscillator was running. I tried injecting a modulated 455 kHz test signal again, coupling the output from my signal generator into the set via a few turns of wire around the DK96 valve. Instead of the pure tone that I expected, there was a beat note from the speaker.  This usually indicates an unstable and oscillating IF stage.

Turning again to the internet, I found several references to similar faults with battery sets in various vintage radio forums. I had already changed the decoupling capacitors and checked screen resistor values, which left possible problems with poor contacts in the valve bases. I gave both mixer and IF amplifier valve sockets a liberal application of contact cleaner spray, and again following suggestions in a forum post, tightened up some of the contacts in the sockets. The advice turned out to be spot on, because on powering it up again I could immediately hear received signals.

It's currently sitting on the bench playing my local AM station on 1332 kHz. The sensitivity isn't great, and i'ts pretty deaf on long wave as well.  I'm assuming that this is because the loop aerials aren't connected, so I'll try it again once its back in the case.

It's been an interesting repair job, but I can't honestly say that there is anything about this set that I like. I'll be quite happy to hand it back to my friend.

Keep listening!


 

Radionette Kurer

It looks like my interest in vintage radios has influenced one of my friends, because he turned up at my house recently with an unusual radio that he wants me to restore. I forgot to take the usual 'before' photo, so here it is almost as received, but without its knobs.

The Radionette 'Kurer' is one that I'd never even heard of before. It's a battery/mains portable from Norway with Long, Medium and Short wave bands, and I would guess that it dates from the early to mid 1950s. It's complete and in reasonable condition, but one of the knobs has lost its brass trim and another is cracked.

The set uses 'D' series battery valves which require 90V for the HT, and 1.5V for the filaments. Batteries for valve radios haven't been made for decades, so the chances of finding a serviceable one today must be very low indeed. Fortunately the mains winding on the transformer seems to be OK, so at least this set should be usable.

It took me a few minutes to work out how to remove the chassis from the cabinet. Eventually I realised that  the wooden panel onto which the chassis and transformer are mounted slides out.

The wires on the left side of the chassis are connected to a aerial  inside of the cabinet.

After the usual strip, dust and clean the first task will be to replace some of the capacitors. Although there aren't any wax paper capacitors in this set there are several brown 'Hunts' branded ones, which in my experience can't be trusted either and usually get replaced on sight.

The smoothing electrolytic is only rated at 150V working. My capacitor re-former won't go this low so this time I will have to bring the supply Volts up slowly using a variac. This trick doesn't work well with sets which have a valve rectifier, but fortunately this one uses a selenium rectifier in the HT supply which will work at low supply voltages.


 I'll let you know how I get on.

Keep listening!