Anyone know anything about 3 gardners transformers I have pictures of?

[CambridgeWorks]

As title.
Weights are:
1869g small, dual lt. 10V 3A dc & 20V 0.6A dc
3630g medium 6.3V 20A
5280g large audio push pull.
Thanks, Rob

[m0cemdave]

That AS 7059 is highly desirable and, if in good condition, worth rather a lot of money to the right buyer...

From the 1971 Gardners AF Transformer catalogue:

Power rating 50w
8K AND 6K6 ct anode load
3.75, 15, 60 ohms output load
Max pri. dc per 1/2 winding 200mA
Prim shunt L (measured @50V 70Hz) 300H nom, 240 min
Leakage L (measured @10v 1kHz)25mH nom, 40 max
Screen taps 20% of 8K and 42% of 6k6
For KT66 and EL34
Freq response "in excess of 30Hz-25kHz" (but no limits/tolerance specified)

HTH

[CambridgeWorks]

Thanks Dave, much appreciated.
For some reason, at the back of my mind I had thought 50W. It is certainly heavy!

I should have asked if any single one is recognised as being from a complete piece of equipment?
Rob

[trobbins]

Perhaps an organ, due to the 20A heater rating.

[CambridgeWorks]

Originally Posted by trobbins

Perhaps an organ, due to the 20A heater rating.

Hadn't considered that.
I was thinking maybe a few KT** plus others in a high power amp.

But, an organ might use lots of ECC8* and as they can be 6.3V or 12.6V I would think a 12.6V would save on heavy gauge wiring?

Anyway, whatever it was used for must have been out of the ordinary.
I wonder if it was a catalogue item or bespoke?

Same applies to the 10V with 20V winding whether made for a specific piece of hifi gear?

Rob

[turretslug]

I wondered if the 6.3V 20A transformer was part of a (serious) power pack involving a floated heater supply for 6080s, 6336s etc. It's still a lot of current though- Bletchley Park could run 100 EF37s from it!

[trobbins]

I have a Selmer 1958 organ with 64x 12AX7, plus a few 6SN7 and a KT66 pair. It has 6.3V 5A, a 3A and a 20A heater, as well as 5V.

Your trio should likely be from a quad of Tx's.

[CambridgeWorks]

Post 7
"Your trio should likely be from a quad of Tx's."

The output one I have had maybe 20 years and the other two bought at different times istr.
Rob

[G6Tanuki]

I can see the 20A transformer possibly being used in a high power RF linear-amplifier using something like a quad of 811-A in grounded-grid class B, or maybe a push-pull-parallel quad of them in a public address/Tannoy* amplifier to produce 300 or 400 Watts of audio for a train station, airport or factory 'music while you work' system..

(The 811-A has a 6.3V 4A heater, as does its successor the 572-B)

*Yes, I know Tannoy is a trademark for a range of nice audio gear but it's also generally used as a term for a public address system.

[Valvepower]

Here we go a salvaged mains transformer from a Selmer Organ. I put the LT loadout coil wire against £1 coin to give an idea of the CSA

Rest assured no Organs were harmed as the amplifier had been long removed from the Organ before I got the amplifier chassis at a Harpenden Sawpmeet. I used the output transformer in a guitar amplifier build which featured in a recent BVWS Bulletin.

Terry

Originally Posted by trobbins

I have a Selmer 1958 organ with 64x 12AX7, plus a few 6SN7 and a KT66 pair. It has 6.3V 5A, a 3A and a 20A heater, as well as 5V.

Your trio should likely be from a quad of Tx's.

[trobbins]

Yes the terminal strip on the top for 20A distribution is the 'tell-tale' for the Selmer organ power transformer. There are different versions, but afaik they all use a top-mounted terminal strip.

The output transformer in mine was 8kPP to 7.5/15 ohm with KT66. A latter version used a larger OT with KT88's.

[Valvepower]

I’m getting mindful of veering off topic…

Attached is a picture of the Selmer Organ amplifier I got at Harpenden.

This uses UL connected EL34s. The output transformer is 6K anode to anode with 40% UL taps.

I used the output transformer in the guitar amplifier project I ramble on about in the BVWS winter 2024 bulletin. I didn’t use the UL taps with this project.

Terry