Astor made a few hot chassis designs.
A couple that spring to mind are the AC/DC portable - the model with the concentric volume and tuning dials on the top of the case and a half-wave selenium rectifier, and the 14" metal case SL portable TV that used a mains transformer just for the heaters - a death trap for the unwary service tech!

Not to mention the poor antenna installers.
Nearly fell off the roof once, grabbed hold of the chimney only for it to give way and slide down the metal roof with me attached.
Yes, 14inch Astor SL !!!
Ribbon cable so if proper baluns had been in use I may have been relatively safe ha ha.
JJ

Yes I can imagine!

Replacing the tuner:

"What are those capacitors in the antenna line for? Don't need them, out they go!!"

I believe that Astor had originally designed the OZ as a hot chassis set, or at least a transformerless set. However, testing proved that getting rid of the extra heat with 240 volt mains in an Australian summer was problematic and the radio had a transformer added for production.

I suspect that a deal had already been finalised with the valve supplier (Sylvania) so the AC/DC type valves were maintained. The low H.T. of the original USA design was maintained, as the type 43 output valve had adequate output at this supply voltage.

Interestingly, the Astor Mickey BE 1935-'36 used a type 41 in the output and received criticism that it didn't sound as good as the OZ. They soon replaced it with the EC (1936) which used a 25A6, metal octal equivalent of the 43.

Cheers.

Yes I once had a really tiny 5 valve pink plastic radio that was basically a Japan / US design, modified to sell in (I think) Hong Kong.

They overcame the voltage dropper problem with a series capacitor.
Warmup was slow but the longer that radio was on, the brighter the heaters would glow because valve heaters, like light bulbs, have a positive temperature coefficient and the series capacitor behaves like an AC constant current source.

Quite alarming to watch and definitely not a Good Idea!

Here are my promised photos. I believe this is receiver number OZ4185 but I will check with the naked eye tomorrow instead of just maxing out the chassis photo because it is inconclusive.

This set has been restored to working order by someone else. Two things I am not a fan of but they aren't important at this stage as I do not regularly use the set. The first is that the earth is soldered to the chassis rather than bolted with a crimp lug. The second is that a few electrolytic condensers are positioned very close to a 5 watt resistor and when these are under load they get very hot.

At this stage I don't have the valve line-up handy but will check this when I get a chance to verify the serial number.

One thing I can confirm is that my set has EC/BP knobs.. The tuning shaft is a vernier with a pointer that moves slower than the tuning knob.

More to come.

By the way: I am happy to lift the image posting limit for this thread. Within reason, this will be unlimited.

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A valve a day keeps the transistor away...

Hi Brad,
Looks like the later 1935 editions did not have the speaker change over switch and extension socket. Also, if the wire wound HT dropping resistor is original it was not mounted on the rear of the speaker.
If the restorer copied the original circuit yours has a cathode resistor and bypass cap on the 43.
I'll post pictures of the speaker with the resistor on the rear.

Does anyone else have an early serial number radio?
See post below for details of the speaker change over switch and knob.

https://vintage-radio.com.au/default.asp?f=1&th=1352

Cheers,
Gary

For the record mine is OZ7522.

Valve lineup is 25Z5, 43, 6B7, 6D6, 6A7 according to the label on the back bar.
Can't see the ARTS&P label, it is not underneath the cabinet; must be inside and hidden.

Back bar label is in good condition though paper has gone brown. Can scan if anyone needs it.

Photos uploaded to Post 22.

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A valve a day keeps the transistor away...

STC830, does serial number OZ7522 have the change over switch and extension socket on the rear of the chassis.
A very good scan of the label on the back bar would be most appreciated?

Thanks,
Gary

"does serial number OZ7522 have the change over switch and extension socket on the rear of the chassis."

Yes, it does. I will take a photo and ask Brad to insert it here.

Will scan back bar label and email soon.

PS Found I had already done the label years ago. Big though, 5Mb jpg. Sent to your email.

These comments are added as an edit to the post to explain the newly added photographs (thanks Brad). The comments are numbered in the order of the photographs .

1. Under the chassis. The 43 socket is second socket from the left. The rightmost tag is for pin 5 and is tied directly to earth; no sign of a cathode bias resistor or its bypass cap.
At the left of the chassis are the extension speaker socket and speaker changeover
switch; connections are removed.
At the right of the chassis the wirewound resistor has been modified by the
addition of a wire tap. The bottom part of the wire coil is broken and the top part
is detached from the top tag of the resistor.
The length of the active part of the coil is about 13mm and has a resistance of 213ohm. The total length of the coil is about 42mm from which the total resistance of the wirewound resistor is estimated to be about 690ohm. The 213ohm part appears to be the cathode bias resistor for the 6A7 below it.

2. Front of the chassis showing bakelite sheet behind the volume control also mentioned in 3.

3. Top of the chassis. Behind the volume control is a bakelite sheet carrying a
resistor and capacitor. The twisted wires on top of the tuning gang are not
soldered at the free end and appear to be a very low value cap as part of
the oscillator.

4. Back without backbar. There is no resistor tied to the back of the speaker.

5. Back of the OZ with the backbar attached. Extension speaker socket at the
right hand end of the back of the chassis. Behind the bakelite sheet cover
is the mains voltage changeover consisting of two screw terminals and the fly
lead which is changed over.

6. A scan of the backboard label. This is a 5.2Mb jpg file and hasn't been processed to improve clarity. This is for anyone who wants to reproduce it and do their own enhancements. Can email the original file to anyone who needs it.

In summary the radio appears to have been original to the published circuit before it was "got at" at the wirewound resistor and extension speaker circuitry. Various apparently resoldered joints hint at other possible modifications so that this radio is not ideal for devining circuit changes over time. That said, all components appear to be period originals.

Here is the text from the backbar of the OZ Radio.
OPERATING DIRECTIONS
ASTOR MICKEY MOUSE.
This receiver is for Use on A.C. Electric Supply Only.
AERIAL: An aerial is provided with the Receiver. In very poor receiving areas a good outside aerial of 25-30 feet long will greatly improve results. Join extra length of wire to aerial provided with the receiver.
EARTH WIRE: An earth terminal is provided, and marked E on the chassis. In some locations an earth wire stops noises.
OPERATION: Tubes require 30 seconds to heat up to full operating con-ditions. Turn volume control fully clockwise and rotate tuning control until a station is heard.
VALVES: This receiver uses the latest 2 in 1 valves including the 6A7 hexode.
SPEAKER: A special Dynamic speaker is built into the chassis. This receiver will give wonderful tone and volume if used with a large remote speaker. With the speaker console that may be purchased separately a special switch over key is provided for changing from the smaller to larger speaker, thus enabling remote operation.
LINE VOLTAGE ADJUSTMENT: There are two mains voltage adjust-ments: (1) 200 volts – 230 volts. (2) 230 volts – 260 volts. Unscrew Danger notice and adjust to the voltage nearest to your A.C. supply.
CAUTION: Never attempt to use receiver with any speaker unless specially designed for the purpose. Otherwise the power transformer and valves may be ruined.

WARRANTY.
This Astor Receiver is warranted by the Manufacturer to be free from defects in materials and workmanship under normal use and service: the obligation under this warranty being limited to making good at the Astor factory any part or parts thereof which shall, within 12 months after delivery of such receiver to the original purchaser (but not more than 15 months from the date of despatch from the Astor factory), be returned to the factory through the under mentioned Dealer and our Distributor with transportation charges prepaid by the original purchaser both to and from the factory, and which examination shall disclose to the manufacturers satisfaction to have been thus defective, this warranty being expressed in lieu of all other warranties expressed or implied and of all other obligations or liabilities on the manufacturer’s part, and the manufacturer neither assumes nor authorises any representative or other person to assume for him any other obligation in connection with the sale of his receiver.
This Warranty shall not apply to any receiver which shall be repaired or altered outside of the Astor factory by any other than the authorised dealer or Distributors in any way so as, in the manufacturer’s judgement to affect its stability or reliability nor which has been subject to misuse, negligence, or accident, nor which has had the serial number altered, defaced, or removed. Neither shall this Warranty apply to any receiver which has been connected otherwise than in accordance to instructions furnished by the manufacturer.
No Warranty whatever is made in respect to wooden cabinets, valves, batteries, chargers, or other accessories not mentioned by the manufacture inasmuch as they are usually warranted by their respective manufacturers.

Photos uploaded to Post 26.

One difference I just noticed is that mind lacks the speaker socket for Minnie. It could have been omitted by whoever restored the set.

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A valve a day keeps the transistor away...

Regarding post 26, I didn't notice that Brad had rearranged the photos in a better order, so that my prewritten comments which I had pasted in also needed to be reordered. This accounts for the editing of the comments in post 26, along with other minor corrections.

Slight accident on my part there - as I usually just include photos in the order they are pasted to Outlook. If you want the comments put after each photo, let me know and I'll change the HTML to suit.

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A valve a day keeps the transistor away...