Help me to identify a transformer.

[Phil Allison]

Bo-Lennart wrote:

----------------

To me it looks more like a tube output transformator, more
than a power transformer.



I have uploaded som picture of the trafo. And I made a
schematic of the
transformer.

Here is the links:

https://i.ibb.co/NKDynrF/20191001-164522.jpg

------------------------------------------

** I will ignore some of your L figures (it's very difficult to measure inductances of the windings on a non-gaped iron transformer, cos they are large an non linear. )

The diagram shows *very* typical R vales for a push-pull audio output tranny of about 60 to 100 watts rating - ie 65 and 59 ohms for the CT primary and 0.66 ohms for an 8 ohm secondary.

The other 4 windings may be also secondaries, allowing various impedances to be added in series or parallel.

My next trick would be to connect the full primary to a Variac and wind it slowly up while monitoring the current flow on a DMM.

Long as the current stays below 100mA all the way to 230VAC, then you can find the secondary voltages, get ratios and be in business.

BTW: what does it weigh?

Any decent 100W valve output tranny weighs about 4 or 5kgs.


BTW2: 70 is NOT old !!



..... Phil

 

[Bo-Lennart]

Den fredag 27 september 2019 kl. 19:48:15 UTC+2 skrev Bo-Lennart:

Hi all out there.
I found a transformer in my basement. I don't know if its a audio-output transformer or just a power transformer.
On top it's stamped "GALVIN MANUFACTURING CORPORATION",
and a model #: "25B31296-E" and a serial# ( ???? ) "138226"
At bottom there is 8 solder lugs, stamped: "1 to 8".
And at one side is 8 screw connector, labeled as "3A 12 11 2B 2A 10 1A 9".

To me it looks more like a tube output transformator, more than a power transformer.
It seems to be from the 1940 or somewhere around there.

Anyone know what it is, and have some kind of "schematic" of the transformer.

Many thanks in advance

Bo-Lennart Karlsson
Falun, SWEDEN

Hi again....
Thank You for all Your suggestion about my transformer.
I would also like to thank You very much for the time You have spend for helping me to identify my transformer.

You had som question to me, and the answer is:
- The inductor-value between 7 and 8 should be in mH (not H) 3,08 mH
- The weight is 2,3 Kg (5 lb)
- Size is: height is 10cm (4 "), base: 8,5 x 9 cm.
I first tried out the transformer as a power transformer like this:
I feed power from a VARIAC to pin 4 and 6. It end up to 230V and the current stay as low as 13 mArms.
- Output at pin 7-8 gave 4,88 V
- All other windings gave 3,66 V
OK, then I tested it as a power output tansformer.
I input: 1 kHz at 1,0 Vrms (+ 2,3 dB)to pin pin 7 - 8.
That gave me these level at the diffrent pins /windings:
- 5 - 4 = 15,43 V ( +26 dB)
- 5 - 6 = 15,37 V ( +26 dB)
- 2A - 12 = 0,69 V ( -1 dB)
- 2A - 9 = 0,69 V ( -1 dB)
- 3A - 11 = 0,69 V ( -1 dB)
- 1A - 10 = 0,69 V ( -1 dB)

So, finally, I think that this transformer is a TUBE OUTPUT TRANSFORMER.
So now I will start to build me a tube-amplifier for my electric-guitar (it's a FENDER guitar).

And PHIL, thanks for Your comment about my age. I know that 70 is just a number. It's how You feel that will tell if You are young or old.

Best regards from SWEDEN

Bo-Lennart Karlsson
Falun, SWEDEN

 

[Phil Allison]

Bo-Lennart wrote:
------------------

- The weight is 2,3 Kg (5 lb)
- Size is: height is 10cm (4 "), base: 8,5 x 9 cm.
I first tried out the transformer as a power transformer like this:
I feed power from a VARIAC to pin 4 and 6.
It end up to 230V and the current stay as low as 13 mArms.
- Output at pin 7-8 gave 4,88 V
- All other windings gave 3,66 V

--------------------------

** That adds up to a 40 watt rated output transformer, with about 4000 to 5000 ohms CT primary.

Try 400 to 450VDC B+ supply and a pair of 6L6GCs, 5881s or EL34s.

KT66s would also be a good option.

Load impedances from 4 to 16 ohms seem possible.

Have fun.


..... Phil