Question about Carnhill VTB 2291 output transformer

[JW]

Hi folks,

Took me awhile to figure out what was going on, but I think something is up here with this Carnhill transformer.  It's a 9600:600 Carnhill VTB2291.

Data can be found here on the aml provided pdf (page7) http://www.audiomaintenance.com/downloads/carnhill_design_guide.pdf

I have two of them and I found out I'm getting pretty different levels through them.

Not connected to the circuit, I'm getting 333 ohms on both coils on the primary side of the first transformer, while the other only reads 8 ohms across both of it's primary coils. The one with lower volume is the one with 8 ohms across both primaries. Forgive me if this is obvious, but an open coil would read infinite ohms right?

But, why 8 ohms? Are the windings just way wrong on this one?

 

[PRR]

DC Coil Resistances: P12:S1:S2 = 315:315:22:22 (Ohms)

"315" and 333 are reasonable agreement.

8 isn't "315", nor is it really reasonable for "22".

Maybe it is a VTB 1148?

Verify what the label says, and *all* the winding resistances, contact Carnhill.

 

[JW]

Okay,

Looking at the carnhill info, and measuring the coils, this is either a VTB 1148, VTB9070, VTB9057, or VTB9049

These are all 1+1:1.7+1.7 transformers. They all measure 6ohm,6ohm:20ohms,20ohms. I don't know how to tell if it's gapped or not though. I haven't been able to get ahold of AML about it. What I want to know is, how do I tell if it's gapped, and can I use it for the output on a G1176 gapped, or not? And if I do, how should I wire it?

It can be wired 50ohm or 200ohm on the primary to 150ohm or 600 ohm on the secondary.

 

[CJ]

just look at  the side of the core to see if it is gapped or not,

 

[ruffrecords]

Carnhill are not infallible. I once had a VTB2291 where the little paxolin board on the top had been put on the wrong way round so the primary was labelled as the secondary and vice versa. They are always happy to put their hand up if they make a mistake. Contact your supplier and I am sure he will replace it.

Cheers

ian