Carnhill VTB9046M line input transformer

I recently purchased a couple of Carnhill VTB 9046M line input transformers. I picked this because it a CPB mounting version of the Carnhill VTB9046 which is pretty much the 31267 line input transformer we used at Neve back in the 70s. I mounted the pair on a PCB with a couple of other transformers from another manufacturer. To my dismay while soldering in the second one its mu metal screen separated from its base (see attached pic). It only moved a short distance because the leads from the transformer to the former stop it.

Now I know for certain the original 32167 was potted and I am pretty certain the current Carnhill equivalent, the regular VTB9046, is also potted but is it looks like this is not the case for the PCB version (suffix M). I cannot see any sign of adhesive so it looks to me like the former is simply a press fit into the mu metal can.

Anyone else had any experience with the VTB9046M?



Cheers

Ian

ruffrecords said:

Anyone else had any experience with the VTB9046M?

Click to expand...

Yes, it has also happened to me a couple of times. I ended up super-gluing it 

But yours looks like it has also been beaten or something.

warpie said:

Yes, it has also happened to me a couple of times. I ended up super-gluing it 

But yours looks like it has also been beaten or something.

Click to expand...

Yes, I had not noticed that until I went back now and looked. You are right it has a deep scratch on one corner. It does not look dented although the photo does make it look like it has been.

Cheers

Ian

[quote author=ruffrecords link=topic=72191.msg914573#msg914573 date=1554495324
Now I know for certain the original 32167 was potted and I am pretty certain the current Carnhill equivalent, the regular VTB9046, is also potted but is it looks like this is not the case for the PCB version (suffix M).
[/quote

If it's anything like the Carnhill mic transformer (VTB 9045 ??)  then it just has some silicon sealant like you seal your bath with to hold it in position, but I would really describe it as potted ....  At least not like the vintage Marinairs that are in a proper can rather than a sleeve.

Rob Flinn said:

ruffrecords said:

Now I know for certain the original 32167 was potted and I am pretty certain the current Carnhill equivalent, the regular VTB9046, is also potted but is it looks like this is not the case for the PCB version (suffix M).

Click to expand...

If it's anything like the Carnhill mic transformer (VTB 9045 ??)  then it just has some silicon sealant like you seal your bath with to hold it in position, but I would really describe it as potted ....  At least not like the vintage Marinairs that are in a proper can rather than a sleeve.

Click to expand...

I agree the Marinairs were definitely potted. I am also reasonably sure the St. Ives ones were too and it was  St. Ives that got acquired by Carnhill.

I have never used the mic transformer (9045) but looking at the pics in the Carnhill Design Guide it does look more like bathroom sealant than potting compound. Carnhill have just gone down several notches in my estimation.

Cheers

Ian

it might be potted, but not all the way,  i bet if you pop the lid you will see some stuff in there,

Marinair used a light oil on the lams and then poly crystal wax to fill the can, i presume the oil was to keep the wax from binding to the high  nickel alloy which would allow the lams to stretch during peak signals due to magneto-restrictive force,  wow, 6 syllables, sounds impressive, 

CJ said:

it might be potted, but not all the way,  i bet if you pop the lid you will see some stuff in there,

Click to expand...

I popped it as far as I could. All you could see was the ends of the wires going to the pins and some fresh air.

Cheers

Ian

well that is strange,  i wonder if they dipped the coil/core assy in air dry epoxy,

CJ said:

it might be potted, but not all the way,  i bet if you pop the lid you will see some stuff in there,

Marinair used a light oil on the lams and then poly crystal wax to fill the can, i presume the oil was to keep the wax from binding to the high  nickel alloy which would allow the lams to stretch during peak signals due to magneto-restrictive force,  wow, 6 syllables, sounds impressive, 

Click to expand...

I have a busted Carnhill 9045 here & the only thing inside it is silicon bathroom sealent.

That's what it looks like

Here is a pic of my broken 9045 inside.  I removed the silicon sealent.  In a nutshell it a plug of sealent to close up the non terminal end.  There wasn't really a lot down the sides of the transformer.

Thanks for the pics everyone. Very instructive. When Carnhill bought OEP I was of the view that this might improve the quality of OEP transformers. Having recently seen many OEP mu metal screened examples I am now inclined to think tOEP could teach Carnhill a thing or two.

Cheers

Ian

I think this has already been discussed but I can't find the info anywhere. Both 9045M and 9046M have pin6 connected to the mu-metal case. Does this have to be connected to earth or to signal ground? The data sheet recommends to connect pin6 to earth but I think I remember reading somewhere that it should be connected to signal gnd instead?

EDIT: Got it mixed up cause there are two pins. 6 & 11.

Can you please tell me what's the best way to connect pin 6 and pin 11?

Both should go to chassis. Neve typically connected pin 6 to a tag held by a screw in the tapped hole in the nearest corner of the the top of the transformer. The tansformer itself was then bolted to the metal work so both the mu metal shield and the transformer core were connected to chassis.

Cheers

Ian