Question about my 1940s Andrea VJ12 TV chassis

[Aussie Bloke]

G'day all.

Last year I picked up from a TV collector an imported late 1940s Andrea VJ12 TV chassis without a cabinet and with 2 radar tubes which were used for it instead of it's 12LP4/12JP4 tube http://www.troysvintagevideo.741.com/andrea.html .

I have since replaced most of the wax paper and bumblebee paper capacitors in the set with mylar caps and have recently unhooked the two mains transformers and tested them and they are working good.

Now I am wondering whether or not this TV set has been modified to run off 240V 50hz Australian standard mains power or if it was left to run off original US 120V 60hz standard mains power which leads to me to my question.

Here below are schematics of the two mains transformers ST-3004 and ST-3005 which I put 120V into using a variac both giving identical output voltages. So here's my question, are these transformers the original mains transformers giving the correct output voltages for the TV or are they modified transformers for Australian 240V standard?

I've got the service manual with schematics but it doesn't say diddly squat of what the transformer's output voltages should be.

Anyhow I hope to get this TV working in the near future should all go smoothly with the restoration.

[earlyfilm]

Originally Posted by Aussie Bloke

Now I am wondering whether or not this TV set has been modified to run off 240V 50hz Australian standard mains power or if it was left to run off original US 120V 60hz standard mains power which leads to me to my question.

You can see pictures of a US VJ12 here:

http://www.earlytelevision.org/andrea_t-vj12.html

Since you can see your power transformers better than I, don't yours look a bit heavier? If so, they probably are 50cps units.

By your tubes, you know your filament voltages.

Since your filament windings popped up at about half filament voltage, I'd say that the power transformers are for a line voltage somewhere near 240volts. You could gently power it up with the variac until the main filaments read 6.3 volts, with 5 volts on the rectifier filaments.

Jas.

[Reece]

Bear in mind that with no heater load on the transformer, you'll get slightly higher than 6.3 and 5 volts at the proper input voltage.

[tubesrule]

Assuming you have a variac, if you have an ampmeter or wattmeter you can determine what the transformers are designed for without any load on them and without risk of damage.

Remove all the tubes, and then power the set from the variac through the meter. For convenience instead of using my DMM I use one of these: http://www.p3international.com/produ.../p4400-ce.html
They are sold for people to monitor power usage around their house. I assume you can get a similar device down under.

Slowly ramp the voltage to 110VAC. The transformer should only be using a few watts in parasitic losses. Now very slowly start ramping up to 220VAC. If this is a 220V transformer the parasitic losses will stay at only a few watts. If it is a 110V transformer, at a certain voltage, probably around 130-140V, the transformer core will saturate and the wattage will climb dramatically. If you hit around 50W don't go anymore to avoid damage to the transformer.
This procedure will tell you which transformer you have.

Darryl