Krone “standard broadcast”

[martinhog]

Hi, I have recently been given a small Krone valve radio. There doesn’t seem to be a lot of information out there on this model It looks like it was “kit built” although from memory it says made in Japan on the case ? A limited circuit diagram and a 2 pin mains plug suggests the whole circuitry is at mains potential. It looks like it has got hot at some time. Does anyone have any comments or observations ? Many Thanks.

[paulsherwin]

It certainly looks Japanese. A lot of cheap Japanese radios of that era had pretty hairy mains arrangements - maybe the low mains voltage used in Japan encouraged a casual attitude.

It does seem to have melted at some stage.

[ms660]

Also branded as Viscount.

Lawrence.

[martinhog]

Thanks for your replies. Considering the mains voltage in Japan is 100volts, it’s probably not a good idea to plug it in ? The previous owner claimed to have used it in The Netherlands . The 2 pin plug is not a European type.

[paulsherwin]

You should certainly check the mains voltage before trying to power it up, which should be easy to do by looking at the heater arrangements. It may well have been built for export to Europe rather than being a Japanese domestic set. I think Japan uses NEMA plugs (2 flat pins).

[ms660]

Some of those Japanese radios made for export for 220-240V mains used a capacitor dropper for the heaters (in part) and the heaters themselves to drop the AC voltage to the rectifier, the dropper capacitor was connected in parallel across the rectifier and the DC load circuit which was then connected in series with the heaters.

Lawrence.

[martinhog]

Hello again,

Here's a picture of the back of the radio. The legend shows 220V on the input and also the mains plug has 220V enscribed on it. I belive ms660 has hit the nail on the head with his power supply description. I was going to carry out some cold DC tests before powering up. Does anyone have some additional suggestions ? Many Thanks in adavance.

[raditechman]

It looks as if the valves in series add up to 121 volts, so should not be connected to our 240v mains direct.
I have on of these radios and when I got it it had been fitted with a line cord to drop the voltage. (Resistive mains lead)
I removed that and fitted a US type mains plug and if I use the set I run it from a transformer.

You could make up a capacitive dropper.

John

[ms660]

There's no capacitor dropper shown in that schematic.

With the schematic as shown I can't see how it can work.

EDIT: Post crossed.

Lawrence.

[G6Tanuki]

The circuit looks all-but identical to what I would expect in a classic 40s/50s "All American Five" receiver.

See https://en.wikipedia.org/wiki/All_American_Five

And yes the heater voltages don't add up to 220/240V so proceed with caution!

[martinhog]

Thanks for all your comments, I will have access to a variac next weekend so after a few DC checks, I will try and power it up gently and report back. Thanks again.

[Herald1360]

The "220V" stamped on the circuit looks like an official afterthought. It might be worth a close look at the actual set to see whether there is a likely looking extra capacitor there!

Powering up from 100-120V on a variac and checking a random heater voltage would give a strong hint though......

[usradcoll1]

Originally Posted by ms660

There's no capacitor dropper shown in that schematic.

With the schematic as shown I can't see how it can work.

EDIT: Post crossed.

Lawrence.

Those things were a poor excuse for an AA5, US type! The 1st IF coil is only that, not a transformer. It also has a very minimal AVC. Even the US short superhets were better than that design.
Many of them were sold as kits.
Dave, USradcoll1