Owner wants me to fix this one. Being a novice, I have had a good look at it, and commenced carefully cleaning it up. Interesting that it has an ECH34 valve (frequency converter?). Any thoughts welcome before I carefully take the plunge.

Cheers to all.
Wodbore

One: Find the model number, that will lead you/ us to the circuit.

Do not power it without assessment. Lots of fixers like me, see the damage that can do. ECH34 Triode Heptode seems odd, but during the & just after war, lots of valve subbing went on.

Thanks for the interest Marcc.
There are no stickers etc that show model number. There is a stamping on the back of the chassis "KM12219". I guess this is a serial number. I downloaded a circuit diagram from radio museum.org which looks about right at a quick check.
I will take my time with this one.
I am a retired electrician, with some left over stuff, but not a radio whizz. My strategy at this stage is to check/replace capacitors and resistors where necessary, and eventually wind it up with a variac.
(No photos yet from Brad - he must be busy).
Cheers
Wodbore

KM is the model: year 1947

6A8, 6B8 6V6, 5Y3 do not run 5Y3 sideways. Sounds like a "reflex" type?

ECH34 is a Triode Heptode

6A8 is a Heptode only and not pin interchangeable with ECH 34. So, unless the pinout has been altered on the socket it won't work. Replace "B" filter caps with 600V types.

Using a 6J8, also a triode heptode in desperation will work, but in many Astor sets being different to 6A8 which is not a particularly good tube, it will throw the band spread of the dial, way off.

Clearly, while the paper caps and electrolytic caps will be history, you are going to have to check the wiring for compliance to the circuit. I have not checked but the info should be on Kevin Chants site.

Powering it is now definitely out of the question. Errors ring alarm bells. Do not remove Philips tubes by the envelope, that can damage the connections to the shielding (metallisation).

Hi Wodbore, have a look at my post in the special projects section 'An Astor Mickey to restore'.
Somewhere around April 2020.
I took a basket case KL and made it work again.
This is probably very close to the KM you have.
I went into the poor thing in great detail and you may pick up some tips to help you.

Cheers, Fred.

Full data sheet: https://www.kevinchant.com/uploads/7/1/0/8/7108231/kl.pdf

Beware: Its back biased, electrolytic cap #20, 24μF does not ground It goes negative to centre tap.

Photos uploaded.

Thanks for uploading the photos.

The tuning capacitor on its side is an unusual sight.

I'd certainly be wanting to replace the 9 orange ducon caps and the black one as well. After that you should measure every resistor and replace anything that's out of tolerance.

There's 3 chassis-mounted electros which should be reformed carefully. If that fails they will need replacing too.

Then there's the possibility of a blown speaker transformer - this should be measured to ensure it works.

I also notice rubber-coated wires which are falling apart - they will need replacement.

I'd say you will have an interesting job ahead of you.

There is a version of the Astor KM with a ECH34 valve.

https://www.radiomuseum.org/r/astor_mickey_km_with_ech34_converter.html

The details for this version can be found in the Astor Technical Bulletins KM-7, 20/4/1949, KM-8, 30/6/1949 & KM-9, 10/8/1949.

I just checked Kevin Chants site but he only has Bulletins KM-1 & KM-2.

I am currently in the UK on holidays. I’ll be back in Oz later next week and I will send a pdf copy of the relevant bulletins to Kevin. I’ll post a link here once it is uploaded.

Just looked at photos in post #1.

That set is in perfect condition compared to the one I brought back to life!!

The electros will probably re-form with careful powering.
I do that by using my Variac and powering up in steps and monitor the power drawn and use a spot thermometer to keep an eye on temp rise.
Start off with 100 volt cross fingers watch current draw or wattage and cap temps.
Then advance to 150, the HT should wake up, clip a DMM on the HT rail to observe.
Leave set for at least 5 minutes between steps.
Any temp rise, smell, smoke, stop and replace.

Caps should then hold voltage on power off and have capacitance.

But first SAFETY. before any power up.
Cut all the 240 wires out and throw in bin.
Leakage test, by megger or HV ohm tester transformer and power switch.
Then connect a 3 CORE power cable with earth wire bolted to chassis.

Most of the resistors will be near enough but most of those wax caps will leak like sieves and need replacing.


Cheers, Fred.

You can download the info from radio museum and compare the wiring of the frequency changer. To ensure it matches the tube. Check the ECH 34 for loose base as that can indicate a breakage of the connection to the metallisation as noted.

As noted with tubes, that during the war we often saw WD scarper off with American type tubes. As there was a Philips factory, several radios had modifications to accommodate Philips tubes to cover the shortage until things settled down after the war.

There is a right and wrong way to deal with Electrolytic caps. I will not reuse the aged Ducon red ones. Many of those early types were allowed to draw 10mA. The electrolytic left unused can explode on powering, or present as a short and as a fixer, I have seen the damage. That's why step one is not powering.

I built a version of Rodney Champness's reformer albeit the 1938 VCT tester also has one. I have reached the point that even allegedly new ones, or those in stock get checked before use. The generalisation is draw in micro amps is 0.01(CV) Where C is in μF and V is voltage applied.

With this reformer (built onto a HV PSU) you can disconnect one end to test the cap in the radio, stepping the volts up slowly (25-400V) and if there is no voltage divider you can use it to power (set not powered) the "B". That can reveal shorts on "B". Reformer will lock up (LR8) on overload.

With a series resistor of 1K the voltage drop of 1 volt across it (DVM) equals 1mA.

Note 50K and 500K resistors of that era, have an attrition rate, along with plate resistors on detector first audio (6B8). Grid resistors on 6V6 (and many output tubes) never leave unchecked.

Wow. Thank you guys for all the advice - it will take some time to digest.

Have done an initial tidy up. Found circuit diagram for Mickey DL at radio museum.org. Quickly realised not the same, and downloaded Mickey KM, and so far a trace seems to confirm.

Thanks again ...... to be continued.

There is a wax paper cap that looks like it's across the B+. It has been getting hot, so it has to go prior to any powering attempts, along with all the other wax papers later in the process.

Looks like someone has already replaced the electros, probably in the late '60s. They are can types and made of unobtainium.

Because there won't be much room to install replacements under the chassis and because they are newer, I'd try a 25 watt dim bulb bring-up with just the rectifier (5Y3) fitted. They may come up OK and save you a lot of grief. If the bulb fades a minute or so after power up, that's a good sign. I'd leave them run for a few hours or overnight so they get a chance to re-form properly.

That big black cap with a band on it is also paper and a type that cracks its jacket & shorts. The two brown resistors should be checked albeit they often look overheated. In overload the one from CT to ground (back bias) can burn. do not increase its wattage: Better it burns than the transformer.

There normally is non polarised cap across "B" often at the RF end. That is for decoupling as the electrolytic is not good at decoupling RF.

Knots in the power cable are now banned, If there are cathode bypass electrolytics, RB types can often be used on the socket (leave its leads long).

Not entirely convinced that a couple of 600V electrolytics won't fit in the pan as the new NP caps being smaller will create space. Do not leave old chassis mounted electrolytic caps that have passed their use by date connected, if you leave them in place

For purpose of inventory & voltage rating I tend to stock one watt resistors. However, on the AGC you often need lower wattage like 1.8M to get the value needed. AGC carries principally voltage more so then current.

Interesting wet day project.