Forgot to put the link into my Post # 12, which I have now edited in. Re cleaning variable capacitors.

Thanks to all who have offered input. All useful. Thanks for references to some of the projects documented on the site here.

I understand the warnings about it being a difficult restore, given it's age, condition and lack of documentation but given it appears to have no great historical value I am happy to have a go at it (ie I am not butchering something of value) and I am not in a hurry - perhaps a case of "Fools amble in where angels fear to tread"

If I make progress (or it descends into a debacle!) I will start a thread as suggested - perhaps as much to amuse the wiser heads here than to inform

A few quick questions here before I finish with my intro thread, if anyone wants to respond:

1. some of the valves look dodgy to me, I don't have a valve tester but starting to see white getter on some of them - how hard is it to source useable older valves like the 1C4 1C6 etc? Most of my (limited) experience is with more modern valves.

2. I am suspecting the vibrator will be U/S (given age and general condition of the radio) , I am assuming I could make a solid state replacement for the electromechanical one and hide it in a similar can - is this commonly done and/or are the old vibrators reasonably robust and worth keeping?

I will put any further questions in the approriate forums, again thanks to all

Jon

Not really answering your questions, because I don't know the answers, but a few closing comments for you.

The last time I tested my valves I noticed that loss of vacuum is becoming a more frequent problem with the oldest valves, and I suspect will spell the ultimate end of them all.

The vibrator should be able to be unplugged - they often use a standard 6-pin socket. Some vibrators may still work, some may just need the points to be filed, while others have rubber or some other degradable parts which will have gone rotten. You won't know until you've opened it - if that's possible.

If the vibrator or associated parts prove too difficult to fix, you might need to make a conventional power supply box with a 6V4 to power the thing. Or even replace the vibrator area with a mains transformer and rectifier diodes.

Anyway we will certainly be happy to hear of your progress (or lack thereof). Keep the photos coming too.

The 6 volt version of the Airzone Shearing Shed Radio will probably be pretty close, circuit-wise. Most radios of this genre had a very similar circuit.

I have an Airzone Radiostar in my collection with the 2V / 135V 402 chassis. It's a good performer as well as being Art-Deco! I restored this radio (only the 2nd radio I ever did) from a basket-case.

The output valve (that you thought looks like a rectifier) will almost certainly be a 1D4.

Don't power up that type of radio with a valve unplugged, the filaments are in series-parallel and you can destroy a filament if you do.

Hi Jon, how many pins does the unknown valve have?
Fred.

The unknown value is in his photos, here: https://www.kellyavia.com/projects/radio/apollo/images/thumbs/38.png

It has 4 pins. If that indeed is the AF amp, then -- as above -- I suggest possibly a type 30.

Sincere apologies GTC et al, sorry to lead people astray, the unknown valve does have 5 pins, in the photo I was trying to see if I could get any indication of the writing on the glass so I rotated it to try and catch that and murphy's law dictated that particular angle perfectly hid the 5th pin

You can just see the bottom the rectangle containing valve identification. Try putting the valve in the freezer for a while. Then take it out and breath on this area. With any luck condensation from your breath will show up the identification for a few seconds. Good luck.

the unknown valve does have 5 pins

In that case type 1D4 is a candidate, as mentioned back in post #6.

Hi Jon, thanks, the 5 pin valve will be a 1D4.
I have a 1D4 in a set and it looks very much the same.

I had a look at the STC 526B circuit, same valve line up but that circuit runs from batteries of 2 volt and 140 volts.
Your set is a battery driven model, probably 6 volts with a vibrator and tranny to give 140 volts.

You need to be very careful here.
As already noted, the heaters of vibrator sets are usually hooked in a resistor matrix to run the 2-volt heaters off 6 volts.
Hint, the resistance of a direct heater is much different cold than hot, so if you measure the heater ohms cold it may look wrong.
Once the heaters reach full heat they settle and draw the correct current and the voltages will then read correct to ohms law.
The 2-volt valves are a bit tougher than the later 1.4-volt types but you still don't want to wind up with 6 volts across a heater!

I did a resto on an Astor MQ farm set with octal 2 volt valves you will find it in the 'special projects' section.
In that I had a broken glass 1M5 and to get the set going I substituted a 6U7 and ran the 6U7 straight off the 6 volt.
I had to put a resistor in the matrix to take place of the 1M5 so the other heaters had correct current.
You can do all sorts of substitutions so long as you obey ohms law!

I also built mains supply to give 6 volts to run the vibrator instead of having a battery.
Should be all detailed in the article.

Cheers, Fred.

Thanks Fred, that all makes sense and very impressed by your Astor MQ restoration.

I noticed the dial bulbs appear marked as 6.8v and are wired (parallel) to battery input so I think you are right, it was intended to be run from 6V battery.

Seems the combination of 2x1C4,1C6,25S,1D4 was pretty common across a number of radios.

I am gradually tracing out the circuit, slow progress. I oscillate between "hey, this is not as hard as I thought it was going to be" and "run away now!"

Hi Jonk,

This radio has an Eclipse look about it. Could even be a Radio Corporation model from South Australia. Have a look at the Croyden 619 radio that’s listed on Radiomuseum.org. I restored this one around 12 months ago and it is similar to your model. This Croyden could run on one of 3 input voltages depending on what was available. A nice radio by the way. Should come up a treat,

Dave

https://www.radiomuseum.org/r/eclipse_croyden_619.html

Thanks Dave, the cabinet and the physical chassis are identical to the Eclipse 619 you have mentioned.

Obviously different circuit but there are helpful similarities.

Photos uploaded to Post 4. Apologies for the delay, as I have just returned home from a break.

Thanks Brad for adding photos.

I have been trying to reverse engineer the circuit of this radio.

I want to make sure I have an accurate representation of the circuit before I
start doing any real work on it.

The process of tracing the circuit has been pretty fiddly and I am sure there
are errors in it simply due to my lack of knowledge and going cross-eyed
tracing where everything goes without doing too much disassembly in case I
cannot correctly re-assemble it!

I am not an electronics engineer and not familiar with older valve gear in
particular and I am somewhat worried about showing my ignorance here for all to
see but if anyone wanted to look at the circuit and offer any insight as to its
reasonableness, needed corrections, obvious errors etc it would be appreciated
- feel free not to be gentle

PDF draft circuit link: https://www.kellyavia.com/projects/radio/apollo/images/pdf/194.pdf

The "Speaker Skt" is the connector to the speaker/output transformer socket.

Most of the circuit I have drawn makes ball park sense to me but I am not
really getting what happens with the 1B5 and 1D4. Does the circuit make sense
there? I understand the 1B5/25S acts normally as both a detector and amplifier
but it seems to be wired a bit differently from what I have seen in circuits I
found for some other radios that use a similar set of valves and I haven't
wrapped my head around it properly.

NB the circuit doesn't have any values for the components (yet) and the
component numbering doesn't follow any real pattern (I just marked each
component on a photo to make sure I didn't get mixed up when working out the
connections - the schematic numbering reflects that numbering).

component numbering see page: https://www.kellyavia.com/projects/radio/apollo/images/wiring.html

Any input welcome!