Output transformer mounting plates

In my 1176's and 1272's the output transformer is mounted on a thin aluminum panel (like a mini front panel) and then that panel is mounted to the pcb or chasis. This serves no real purpose that I can tell, however since more than one has done this, identically, there must be some logic behind that construction that is lost on me. I dont know too much about transformers, perhaps it has some kind of shielding effect but its hard to imagine.

Anyone have any idea why this was done or if there is any advantage to doing this? On the 1272 at least, the plate was tapped for 4 bolts, so its definitely a sturdier mount for the transformer compared to just the 2 points on the transformer bracket, but wondering if its just as simple as that.

Ive got to mount a bunch of transformers that have these plates and would like to know why they were put in there in the first place before discarding them. Mounting the transformers without the plates would be a lot easier.

thanks

dave

Dave,
I think that the only purpose served by using those plates, is that it allows smaller screws to be used for the mounting.

peter

Perhaps it helps displace the weight of the transformer over a larger and more sturdy metal area rather than mounting the transformer directly to the PCB which is not as strong a material as metal. As to why you would need it to then mount on another metal peice, I'm not sure.

T

HI Dave

The aluminium plate on the Original Neve LO1166 is used to apply more even pressure on the I section of the EI core so the gap for the DC stays more constant. The normal EI frame wrap has 4 tabs that would be folded to hold the I section in. The LO1166 doesn't have these tabs instead fibre packing is added under the I core and then a aluminium plate to hold it all together under pressure as well as some epoxy coating. Removing the aluminium plate pressure you will see a inductance drop as a the gap moves usually unless the epoxy is holding on well.

You will see this also in early 1176's with Class A amp I am told as they have a DC gapped transformer.

If you were feeling game you could take off the plate after measuring the inductance of one winding and when it is rebolted up check the inductance is the same. If it is less inductance place some more packing under the transformer and do it up again and recheck.

The aluminium plate on the neve has 4 screws because you cannot have bolts in the centre of the top and bottom panels in neve modules or it would foul the tongue and groove slides.