Impossible output transformer

[gja]

Hi guys,
I know there’s a zillion posts about unknown transformers, and how to work out the turns ratio etc...but just cant get my head around this one.
It came with a 2x6sk7 2x6v6 amp I got on the bay umpteen years ago.
I had marked out the secondary side but assuming it’s a pp transformer I cant figure out which one is the b+.
I get all sorts of readings which don’t make sense ( ex 1,5k if using pin 3 as b+ and pins 1 and 7 for anodes).
Maybe I am assuming wrong and this was a parralleled se amp.
Anyway, the combinations between pins is just too vast for me to understand.
Pin 4 is the only one that goes nowhere (no resistance reading between any of the pins and nr4).

Any help would be really appreciated and sorry if this is just another guy trying to figure out an unknown output trafo...

[kagliostro]

Maybe pin 4 is the connection to an internal shield that is to be connected to ground

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About other pin

use your ohmmeter and draw on paper the numbers of pin that are connected each other, it will be nice also if you can write the resistence between pins that are connected to the same winding (but to measure such a low resistence you require a special tool)


if you can do this, indicate which pins have the thinnest wires connected and which the biggest wires

Post here the paper with your notes

Franco

[gja]

Hi Franco,
Can’t see the thickness of wires unfortunately ...
Attached my readings, again number 4 is isolated from all the rest.

Thanks in advance for your help!

[jjasilli]

Assuming you know the secondary side, put a low voltage into that: say, 1 - 6.3VAC.  Then use a DMM on the primary side to find the HT wires.

[shooter]

here's a schematic image for crayoning 

[kagliostro]

The numbers of interest are

1-2 = 107

1-3 = 107 (??)

1-4 = --- (looking the photo seems that pin 4 is connected to nothing - no internal shield to be clare)

1-5 = 121

1-6 = 156

1-7 = 180


So all the pin are connected, in different point to the same winding (except pin #4)

You wrote 1-3 = 107, (the first number looks like 1 -- 107) that seems odd, please can you verify

Other question for you, do you see a pin where there is soldered more than one wire ?


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To establish if is an SE or PP transformer look to the laminations, if E & I are mixed the transformer is a PP if E & I are all on the same side, all the E together and all the I together, it is an SE transformer

Franco

[gja]

Yes. pin 4 is connected to nothing...

Kagliostro, I forgot to check that 1-3 this morning...

Attached are my readings with 5v applied to secondary and bottom frame removed to show the core stack.

Difficult to see if more than one wire is soldered to a single pin.

[kagliostro]

Laminations are interleaved, so PP transformer

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Waiting for the resistance measure pin 1 - 3

Franco

[gja]

Hi Franco,

1-2 = 39 ohms

Hope this helps

[shooter]

IF you can open a word doc., here's fun with transformers ;

[kagliostro]

1-2 = 39 ohms

Hope this helps

I was asking for 1 - 3 .....

Before 1 - 2 was 107

now you say 39

which one is correct ?

Franco

[Williamblake]

Attached are my readings with 5v applied to secondary

Why don`t you have 5V in the drawing then? It is easier to tell what`s going on if you had a drawing where one could _see_ the connections between pins (like lines) an the resistances between pins.

[shooter]

what tabs did you apply 5vac to??

[gja]

Confirm mistake was between 1 & 2 and it is 39.
1-3 is 107
I applied 5v to A & F because I could see they had some soldering on...just guesswork.
Attached drawing...

[PRR]

Don't see how it fits 2*6V6, but here's numbers:

[shooter]

I had marked out the secondary side

against what?  A speaker soldered to it?, a 1/4 jack labeled speaker?

where on the chassis was it mounted, if you recall?

[kagliostro]

What is this ?

Seems that an additional wire is connected to pin #3

--



So an UL OT with 35% intakes

--

Impedance seems more fine for 6L6 tubes

Franco

[gja]

Franco many thanks 3 as CT is what i suspected...

Cant see any additional wire soldered.

Shooter it was mounted on little chassis and the guy who sold it to me had marked "to speaker " on the secondary side.

How is the secondary configured? There´s a jumper between B and H and between C and G.

If anyone can draw out how this works between different windings i ´d really appreciate learning a little more.

I suppose you can change the impedance used...

[kagliostro]

Ciao gia

Franco many thanks 3 as CT is what i suspected...

Not me, PRR did the job before I was able to arrive to a definitive clue, you have to thank him

Franco

[gja]

Thanks PRR and everyone !!

[kagliostro]

🙂👍


Franco