I am restoring my OZ and have noticed some circuit differences to the published schematic.
I have checked the circuit of two OZ radios over here in WA and compared them with the one the Silicon Chip article, all are slightly different.

http://archive.siliconchip.com.au/cms/A_100857/article.html

So, if other OZ owners are interested and would like to check their OZ circuits we can build up the modifications over time with reference to the serial number. It is essential that the modifications are original and look like they made in the 1930’s using cotton covered wire and old looking solder joints.

I’ll get Brad to post the original schematic and my radio, Serial # 3381.

Astor OZ Original Schematic:

Astor Mickey Mouse OZ Circuit Diagram

Serial Number 3381 Schematic:

Astor Mickey Mouse OZ 3381 Circuit Diagram

Serial Number 3381 Pictures:

Photos and documents uploaded.

Observations on the OZ radio in the Silicon Chip article, Serial Number 5753.

1. No speaker change over switch. Still has rear speaker socket?
2. No resister mounted on rear of Jensen speaker as per Serial Number 3381.
3. Not possible to see Pin 5 on the 48 to see if it has a cathode resistor or is earthed.
4. Deadly two pin power socket is used.

I hope other Astor OZ owners will detail observations on their radios?

Observations on OZ radio Serial Number 7672.

1. No speaker change over switch.
2. No resister mounted on rear of Jensen speaker as per Serial Number 3381.
3. Not possible to see Pin 5 on the 48 to see if it has a cathode resistor or is earthed.
4. Extension speaker socket and two pin mains socket covered.
5. Can with two filter electrolytic capacitors is used.

Photos uploaded to Post 6.

I've taken some photos of mine. I'll get a few more tomorrow before putting up tomorrow night.

I see with one of those, a hole drilled for a cable. I wonder if an IEC socket would fit in that original hole? The transformer is shown as "shielded" & they always bleed charge onto a chassis, an earth wire would get rid of it.

Looking at the back of that hole where wire still is, that can twist & a gland may be a better option. Even none of those are original to that era.

I've always thought the use of the 25Z5 rectifier in the Mickey was intriguing.
Sure it was an indirectly-heated rectifier but in the transformer design it needed its own heater winding anyway. So why bother?
Obviously predates the 6X5...

25Z5 pre-dates 6X5 by 3 years. 6X5 was designed for car radio's originally, which was interesting as some mechanical variants of it, were notorious (from info on the American forum, particularly in Zenith radios) for heater cathode shorts & the impending destruction of transformers when they did.

Yes the well-known 6X5 heater snake. Looks quite alarming when you first see it but it usually doesn't stop the valve from working...
Does anyone know why the 6X5GT was so prone to the heater popping out the top of the cathode like that? It only ever seemed to happen with the early version that had the two flat anodes, not the later re-packaged 6X4 "X" anode construction.

I have a 1930's car radio that has the -G version of the 6X5. Bottle-shape, 4" long. Only one I've ever seen...

Getting back to the strange choice of the 25Z5, the 6Z4 (84) was available at that time and had a 6.3v heater.
6Z4s are still available.....

Maybe it was just more expensive and the lower cost of the 25Z5, due to its higher volume, justified the addition of an extra heater winding on the transformer. But if you needed to add a winding anyway, why not make it a 5v one and use an 80? Would have been cheaper....

Maybe we will never know....

The 25Z5 was used in most Astor's in 1933, 34.

Maybe they had acquired a stash of them in readiness for a hot chassis version that never eventuated. Happens.....

The Silicon Chip article states under Australian modifications.

“This receiver was, as mentioned earlier, an "Australianised" version of an American radio. The American design was for a transformerless set which ran directly off the 110V mains. In this design, the valve heaters would have all been connected in series, which meant that 69V was needed across them for best performance (possibly achieved by using a dropping resistor).

Modifying the set for Australia involved adding a mains transformer to supply the voltages required. This transformer allowed the set to be used with the Australian 240V mains and featured three heater windings to cater for the various heater voltages. In addition, the rectifier circuit was modified to function as a full-wave unit, instead of the half-wave unit used in the original design.

However, some later versions of this radio used valve heaters that were wired in series and a half-wave rectifier was used to supply the HT voltage for the set. These later receivers were very much an American design, with a power transformer "hung" on the mains to give the right voltages. As before, it was no longer necessary to use a dropping resistor to reduce the 110V to 69V as the heater winding on the transformer provided just the right voltage.

The power transformer probably fitted in the space vacated by the heater dropping resistor in the American sets. And as well as providing the correct voltages, it certainly makes the set safer to work on. Indeed, Australians have always had a dislike of live chassis equipment, in contrast to the Europeans and Americans.”

Has anyone come across an OZ that has its filaments wired in series and a half-wave rectifier used as described above?