50watt partridge transformers. Help please =]

[The Dude]

Pure speculation, but it might help.

I'm thinking on the power transformer secondary.

Green wires = filament winding
White wire next to greens = filament CT
Brown wires = bias supply winding
Red and Black = B+ winding

[g1]

That could be. One thing that bothered me was this: he said from white to black on PT he measured 0 ohms. I don't think that should be.
For safety, I would suggest he check resistance from frame to every wire on both transformers. Report any wires that show any resistance to the frame.

[Yrps]

Alright. I tried the transformer trick and still couldn't get a reasonable voltage. I picked up some extra cash and I'm getting a Variac today. I live in Australia and this seems okay, 0-260VAC Variable Laboratory Autotransfomer (Variac) - 500VA - Jaycar Electronics

[The Dude]

Probably a moot point since you ordered a variac, but a higher voltage transformer should have worked just fine. If you couldn't get that to work, something must have been wrong, and I'm thinking you'll have the same problems with the variac. I'm curious:

1) What transformer did you use?
2) How did you hook up for testing?
3) What did you use to measure voltage and what meter settings?

[Yrps]

Haven't ordered the variac yet. I purchased a similar transformer as recommended. Mains in, 12.6V out @ 3oomV. Put the 50Hz sine wave in both combinations (before attaching to 50watt transformers) and had less of a AC voltage out than before.

[The Dude]

When you say "Put the 50Hz sine wave in", what are you referring to? Are you still using the test tone maybe? FYI, with the transformer, we no longer use the test tone, if that's what you are referring to. We use AC from the wall. The transformer outputs a lower AC voltage for testing. The reason we do this instead of simply plugging the partridge transformer into the wall is because we have no certain idea what windings are what, and we don't want to damage anything by applying a large voltage with high current capabilities.

So we have this:

Mains (wall) input to primary of whatever transformer you bought for testing > secondary of this transformer to primary of partridge transformer > knowing the input to the partridge transformer, we measure the output.
We then calculate the ratio (input to output). Using this ratio, we can figure out which input wires and what voltage will give you a desired output of the secondary.

Again a reminder: Be careful not to touch any wires while testing. You are dealing with potentially lethal voltage.

[Yrps]

Yeah okay. That makes sense then. Well, it makes sense to get a Variac then, so I can control the Voltage and not kill myself initially. I got a scrap piece of wood and some nails for a bread board. Looking for help with this test idea

Variac>kettle chord>breadboard mounted plug/input>to transformer

With that last part what do I want to use as a conductor/to join those points together?

[g1]

You bought that transformer so you wouldn't need a variac, try it!
It will give you the equivalent of 10% of line voltage. You wouldn't go much lower than that with a variac anyway.
Just excercise normal caution, same as you would need to with the variac.

[mhuss]

On the SC Partridge PTs I've seen (including a 50+), the heater wires are usually green, and noticeably thicker then the rest of the wires. Unfortunately, they were often wrapped in green sheath in the amps, so 'gut' pictures won't really help.

[Yrps]

Okay I think I've got it. If I buy one of these Jaycar Electronics - Search results
then

Power line filter>mount on breadboard>solder/attach lines from transformer>secondary coil to primary of partridge

Is this about right?

[Yrps]

Okay I think I've got it. If I buy one of these Jaycar Electronics - Search results
then

Power line filter>mount on breadboard>solder/attach lines from transformer>secondary coil to primary of partridge

Is this about right? and will I need a fuse?

[g1]

That will do it. Or you can just solder up a 2 prong AC cord to the primary of your 12V transformer. I usually cut them off stuff I'm junking just to have for such uses.
A fuse could be used in series with one of the 12V transformer primary leads if you want. It would have to be quite small value to protect the 12V transformer, like 1/10 amp or something. Even 1/2 amp will probably suffice.

[J M Fahey]

If you are absolutely certain that you can work with live 240V mains driving the transformers under test, I can post the schematic and instructions on how to do it, without a variac (which, by the way, still furnishes live direct from mains voltage, variacs are not line isolators by any means)

You will need a lamp bulb limiter (build it anyway, you will use it forever) Light Bulb Limiter and a piece of wood with some nails in a row, to which wires can be soldered, I don't want wandering wires with exposed ends wandering around.

If so, just whistle .

Edit: given that 240V is the test voltage, all others are easy to measure and with great precision.

And yes, you will measure both PT and OT

[Yrps]

That's why I want a Variac, I'm pretty comfortable around mains. I keep the shed Isolated when working under dangerous conditions. But a Variac seems safer as you can control the voltage you're working with. If you could post that schematic that would be great. The lamp bulb limiter looks like a good idea. I'll fetch those parts as well.
Thanks for the help. You're all legends.

[Yrps]

Do I want a stdp switch for that bulb limiter?