What's the best way to attach the power transformer to the chassis?

[motzu]

Hello,

first of all, this is the type of PT I'm talking about:



I've seen a few examples where the transformer screws are inserted into the chassis from the back just the way it is in that picture (with the screw nuts unscrewed before inserting the screws in the chassis holes), and then fixed with a second set of nuts from the inside. And a few examples of PTs fixed on the chassis with a single set of nuts from the inside.

What's the wisest method? Would using two nuts for every screw make the chassis more susceptible to unwanted rattle at louder volumes? Would it be better because the PT is further away from the chassis, thus not raising the chassis temperature as much, and inducing less current?

Is this even something worth worrying about at all?

Thanks!

[txstrat]

I usually use the nuts the PT came with and leave the plastic (or rubber) washers on the outside of the chassis (that way I hope the vibrations are kept off the PT for a good amount). The nuts hold best with star washers. Had no issues with this method so far.

[Bruce / Mission Amps]

Shove it in place just the way it is. Don't remove any nuts from the stack studs.
Let the PT float above the chassis the thickness of the existing nuts and then on the inside of the chassis use KEP nuts to mount it in place.

[motzu]

That's what I thought, thanks for replying!

[txstrat]

Don't remove any nuts from the stack studs.

To my excuse I must say, the german nuts have different threads than the studs on the Hammond transformers I usually use. I could get fitting nuts in a shop out there but that would be a day trip. Haven't considered it necessary, yet. Seems I gotta go and get some to stockpile.

[Bruce / Mission Amps]

Yeah I bet you're right, the Hammond trannys use North American standard 8-32 thread the Euro studs are probably Metric.

[motzu]

OK, but who's to prevent you from buying both studs and nuts and replacing the original US studs with close-enough metric ones? Should be a pretty easy find at most hardware stores.

[txstrat]

Usually the studs are not long enough (that means they have a max. lenght for each diameter - I'm sure they can get me some longer ones on special order but that would make it more expensive) but I could go ahead with threaded rods and some nuts as well.

[Diablo]

To my excuse I must say, the german nuts have different threads than the studs on the Hammond transformers I usually use. I could get fitting nuts in a shop out there but that would be a day trip. Haven't considered it necessary, yet. Seems I gotta go and get some to stockpile.

Can't you order hardware parts (nuts and bolts etc.) via mail order in Germany? I can get on the web and order darn near anything from Mcmaster Carr and have it delivered to my house the next day.

[Enzo]

he could even order them from the USA. But I'd feel pretty silly placing an order somewhere for four nuts.

The local hardware or Home Depot in the USA has both metric and Imperial nuts. Are 8-32 nuts not available at local retail in Erope?

[overtone]

Usually the studs are not long enough...

Your simplest way may be to search for "8 32 nut" on the German or British Ebay sites.
I have the same issue here in Germany with a MM PT for the next build and an Ebay search in both locations came up with a number of sources.
+1 for Bruce's recommendation to use a toothed nut. A toothed nut, toothed washer or even a nyloc-nut is good advice.

(I have to check if that MM PT is also needs 8 32 nuts.)

[txstrat]

But I'd feel pretty silly placing an order somewhere for four nuts.

That's right, the shipping would be way more than the amount of the nuts and bolts, even if I order more than one set.

The local hardware or Home Depot in the USA has both metric and Imperial nuts. Are 8-32 nuts not available at local retail in Erope?

Yes, they are available. I know of a shop (where I've already bought some stuff) in the town where my father in law lives (I'm pretty sure there would be such a store in my town, I just don't happen to know where). I usually combine a visit at his place with a visit at the hardware store. I think next time I'm gonna buy a couple of the proper nuts.

[txstrat]

+1 for Bruce's recommendation to use a toothed nut. A toothed nut, toothed washer or even a nyloc-nut is good advice.

I agree, when I mentioned "star washers" in post #2 I was referring to "toothed" washers. Haven't considered nyloc-nuts yet, because of the heat in the area around the PT.

[Wombaticus]

Shove it in place just the way it is. Don't remove any nuts from the stack studs.
Let the PT float above the chassis the thickness of the existing nuts and then on the inside of the chassis use KEP nuts to mount it in place.

Just wondering why you prefer this method.... The few times I've used a laydown PT, I just removed the nuts to flush the lams with the chassis to provide a bit more heatsinking. Do you reckon this is a bad idea? Seems to work fine.