Can anyone ID this transformer?

[(*steve*)]

I have two of these transformers and I'm after some further information if anyone has anything.




The high voltage secondary is marked as 250-0-250 and 60mA DC.

There are three other secondary windings, 0-4-6.3 2A, 0-4-6.3 3A, and 0-4-5 3A.

I'm curious about how to understand the rating for the high voltage secondary. And some documentation...

 

[Minder]

What else is there to know? The ratings are on it?
The 60ma rating will be for 250v, the L.V. secondaries will be at the highest value in each case.
The VA at each tap setting can be extrapolated.
Including the total VA for the transformer.
M.

 

[(*steve*)]

The problem is that one can rectify the output of this transformer in multiple ways. To which configuration would the 60mA refer?

I'm intending to full wage rectify the 500V to get approx 700V DC.

The circuit it was in half wave rectified the secondary (with semiconductor diodes) and regulated the output with OA2 tubes. The OA2 tubes have a max current of 30mA, so I guess the max output was no more than 25mA to 30mA (since the power supply could be operated unloaded)

It would be a lot easier if they gave the max continuous AC current for the high voltage secondary.

 

[Minder]

If not loading it up to the full Va via the other secondaries, you could go a little higher on the 250 sec. the limiting factor is the wire gauge but you would see this with a volt drop if exceeded too much.
M.

 

[73's de Edd]

Sir Steve . . . . .

In referencing the wiring hookup, that the LAST person used:

On the transformer primary looks like they could have used O as AC low and an optional 200 or 220 or 240, for AC HI, but instead, he opted for using that far left offset of 10VAC and the 220 to get himself a 230VAC input.

On that next row up, the BROWN wire was his OVAC and then he took off 6.3 VAC at up to a 2 amp capacity with the YELLOW wire and then he used the GREEN wire along with the The BROWN OVAC common wire already established , to get 30 or 70 VAC . . . (its being obscured, what it is ?) . . .for a SCR supply voltage that the unit was intended to be used with. *********

Then move to the top row where you have the two RED wire AC voltages either side of their central C common centertap. Figure on that AC voltage rectifying via fullwave rectification to end up with a DC supply of ~250VDC a ~ 60 ma capability.
On the final bottom row looks like he shared / established that AC supply common starting at the left BLUE and GREEN wire pair with the GREEN joining to the B+ supply common ground.
Then he joins the bottom of that 6.3 VAC tap to the O of the common like supply to the right to make it series aiding output and finally takes off 6.3VAC + 5VAC at the far right BLUE wire.

********** All of your voltage and current specs are being given excepting that "SCR" winding.
Sooooooo power up and measure that summed AC voltage from the left "0" to the GREEN wires as the summed up AC SCR voltage.
Take that AC voltage just being measured . . .as unloaded . . . across that path just given, and load it down with combinational power resistors until you have dropped it 10% and then compute the volt and current specs for that degree of loading upon that SCR winding.

Thassssit . . .

73's de Edd

.

 

[bushtech]

That transformer is a work of art

 

[73's de Edd]

Yep . . . . . that is beeing one cojoined parental effort . . . . . Mom worked in a molasses factory and Pop worked at an arsenal as a hand grenade assembler.

 

[Minder]

I took SCR to mean Screen, IOW electrostatic shield??
Also has a connection to the frame bolt.
M.

 

[kellys_eye]

Yeah, the DC designation is a funny one..... but given it's a centre-tapped secondary we can assume a fullwave rectifier feeding either a capacitive smoothing circuit in which case the DC load capacity is going to be the stated 60mA and 350V DC out.

With a choke input filter your DC will fall to around 250V DC but the current will be 50% higher.

Gardiner transformers are a real work of art - very sought-after in the valve (tube) communities - I sold one recently for well below what could have got (as I subsequently found out )

 

[(*steve*)]

It looks like a reverse engineering of the circuit may be in order.

I have 2 of these from 2 different power supplies. I'll reverse engineer the simpler one first

 

[(*steve*)]

Some photos of the simpler of the two units:

 

[hevans1944]

Steve, do you even have a boat to use these transformers as anchors with?

 

[73's de Edd]

On that board portion that you show . . . . .indeed a B+ supply, with a full wave rectifier pair to get initial B+ then an inline HF inductor to an initial 22 ufd of filtering into a 7K filter resistor with a possible like 22 ufd of final filtering.
That developed B+ then regulated via a series pair of stud mount zener diodes.
Confirmation of that ' SCR ' as electrostatic shield to chasis ground.
FIO . . .But what was that number value beside it.
Unit visualises as 1961'ish design and construction.
NOW the other board half ? to see how the lower voltage aspect was treated.

 

[(*steve*)]

Here is the reverse engineered schematic.



I'm pretty sure it's accurate (it's not, see below).

The device was last "checked" in 1990, and so was probably scrapped within 5 years of that (assuming a 5 year cycle for electrical safety checks which is about what I've seen in this environment).

The other (more complex) unit is significantly different, but getting the schematic for it might have to wait a while...

(I apparently have jobs to do)

And here is the corrected version:

 

[kellys_eye]

Got to love the 'space optimisation' they employed in those days!

Schematic seems just fine - is there a particular issue with it or was your query just about the 'DC' spec of the secondary winding?

 

[(*steve*)]

No, just about the meaning of the DC spec.

I'll reverse engineer the other box tomorrow. Same transformer, but significantly different circuit.

 

[hevans1944]

Amazing find! It is clear from the low-voltage secondary windings that this high-quality transformer was intended to power vacuum tubes in its original incarnation. The 5R4-GYB full-wave duo-diode rectifier was the usual choice for DC rectification, but it required 5 VAC for its filaments. Almost every other tube required 6.3 VAC, but I have no idea what the 4 VAC tap powered. Maybe some "old timer" here will remember and fill us in on that.

The very first "serious" power supply I built, circa 1964, used a 5R4 rectifier and two power transformers salvaged from defunct television sets. My rectifier was a "military surplus" version of the 5R4, easily identified by its cylindrical bottle with the flat-top end. IIRC, I later substituted silicon diodes for this vacuum tube rectifier, but that was pretty much my last adventure with vacuum tube home projects. The power supply was connected to my home-brew, crystal-controlled, 3 MHz, CW (80m Novice band) transmitter, providing a variable, regulated, positive plate voltage up to about 400 V DC at 250 mA or about 100 watts to an RCA 6146B final amplifier operating in Class C bias. Novice amateur radio licenses in 1964 required somewhat less power input to the "final," 75 watts (maximum), hence the need for an adjustable plate voltage.

So, Steve, what are your plans for your two treasures?

 

[(*steve*)]

So

Nothing really exciting. I have some dekatron and some nixie tubes and I plan on making a clock. I plan on doing the division and digit driving using the dekatrons rather than logic.

I could use a DC to DC converter to create the high voltage, but these transformers look a lot better

 

[(*steve*)]

Here is the other unit:

 

[(*steve*)]

And the schematic for the other unit:



I don't have a symbol for the tubes, but they're just big zeners, so that's OK.

Note the -6.2V output. I rechecked and that;s the same on the other box... I got that part of the previous schematic wrong (I may update it later).

I'm pleased that both circuits rectify the high voltage in the same manner. If I assume that's what the 60mA is based on, I can do some calculations to figure out what I can get for other configurations (and that was my goal).