RS transformer info

[pwdrive]

I would measure them again, don't try and measure current across any voltage source....!

Lawrence.

[Bushbaby]

Is there any combination that I should measure in particular?

[Nick]

The red-black-red looks like 250-0-250, which is why I would have expected there to be two thin blue wires for red-blue-black-blue-red for 250-135-0-135-250... hence asking for red to thin blue, which should be 115 or 385 (depending on which red you chose).

If the thin blue winding is all on its own, then you'd get 385V from each red to thin blue.

[pwdrive]

Is there any combination that I should measure in particular?

Red-red-black all seem ok, forget the thin blue wire it won't come into the equation.

So, check grey to grey again.

Then check white to thick blue and white to thick green again.

Post those measurements.

Lawrence.

[Nick]

Mercury Magnetics seem to be re-making a lot of the old RS transformers - see http://www.mercurymagnetics.com/pages/ca...spares.htm - scroll down - there are transformers there that are very similar to yours...

The secondary rectifier heater supply seems to be (all thick wires) blue-green-white for 0-5-6.3 (when under load)

[pwdrive]

Typical Radiospares transformers and specs back in the day:

http://www.electrojumble.org.uk/DATA3/RS...s_1967.pdf

It's possible that the green, blue, white is 6.3 volts and 5 volts with a common connection, if so then that would be the rectifier heater windings, eg: for a 6.3 volt heater rectifier or 5 volt heater rectifier, that would make the two greys a separate 6.3 volt winding for the amplifying valves. ie: the 6th specification on page 2 in the link.

Lawrence.

[Bushbaby]

Ok, I've tried every combination measuring in AC volts

Blue to Green - 5.5v
Blue to White - 6.8v
Green to White - 1.23v
Blue to Grey 1 - 59.7v
Blue to Grey 2 - 63v
Blue to Red 1 - 325v
Blue to Red 2 - 75.5v
Blue to Black - 125.2v
Blue to thin Blue - 200v
Green to Grey 1 - 63.5v
Green to Grey 2 - 66.6v
Green to Red 1 - 333.6v
Green to Red 2 - 72.6v
Green to Black - 131.5v
Green to thin Blue - 207.7v
White to Grey 1 - 63.7 v
White to Grey 2 - 67.5v
White to Red 1 - 338v
White to Red 2 - 71.5v
White to Black - 133v
White to thin Blue - 206.5v
Grey 1 to Grey 2 - 6.91v
Grey 1 to Red 1 - 178v
Grey 1 to Red 2 - 111v
Grey 2 to Black - 40.5v
Grey 1 to Black - 31.6v
Red 1 to Red 2 - 517v
Red 2 to Grey 2 - 102v
Grey 2 to thin Blue - 111v
Red 1 to Black - 259v
Red 1 to thin Blue - 73.3v
Red 2 to Black - 259v
Red 2 to thin Blue - 327v
Black to thin Blue - 127v

I think thats all.

Regards

[Refugee]

Blue to green rectifier heater 5V
Blue to white rectifier heater 6.3V
Grey to grey main amp heaters 6.3V
One red per rectifier anode and black to chassis with a fuse.
Measure the thin blue to all other windings with 2 meg ohm range. You should get more than 2 meg. If so it should go to the chassis.
If you can try all the AC voltages again with a moving coil meter. All the rest of the voltages will be much lower as they will all be caused by DVM confusion. Modern volt meters are too sensitive for this sort of work.
An AVO 7 would be best if you have got access to one.

[Bushbaby]

Yes, I do have an AVO7 so I shall repeat the exercise again this evening. Off to Gloucester now about a new work project.

Regards

Rob

[ppppenguin]

There is no point in measuring voltage between points that aren't connected to the same winding. As established by resistance checks without power connected. Such measurements will only confuse both you and us.

Using a DVM to measure between unconnected windings will give all sorts of spurious readings due to stray capacitance between the windings. Yes, an AVO7 should read zero on all such measurements but that's not the point, the "measurements" shouldn't have been made in the first place.