Dumb question re: mounting PT

[mhartman]

Do you remove the factory nuts on the thread end of the screws to mount it flush, or do you leave them on (thus causing them to act like small spacers).

I know, dumb question, but I want to get it right.

Thanks,
Mike

[selloutrr]

Assuming the transformer is a lay down style. You remove the nuts and use them to mount the iron flush. Reinstall the factory nut

[mhartman]

Yes, it is a lay down style. Thank you!

[tubelectron]

Assuming the transformer is a lay down style. You remove the nuts and use them to mount the iron flush. Reinstall the factory nut

And if the chassis is steel, it will act as the latest lamination of the transformer and may induce hum, so it would be better to

leave them on (thus causing them to act like small spacers).

and use an additional set of nuts. I fronted the problem with several VOX AC30 from the 70's, where both power and output transformer where flush mounted, the later one induced quite audible hum in the first one via the steel chassis... Spacing both from chassis was the solution.

Of course, it's useless if your chassis is made of non-steel metal (aluminium, brass), you guessed it.

Another problem may arise, more often on old/used trafos : releasing the bolts just for the mounting time may left the transformer noisy/vibrating after, if the dipping/coating is poor or non-existent. It should not happen with recent quality transformers, well impregnated, but sometimes...

Lastly, I found more easy to install and remove "spaced" transformers than flush ones : only 4 nuts and 4 washers on one side.

That's why I prefer the "spacer" solution...

[M Fowler]

I leave the nuts on and add nuts.

Some times they come with the transformer and mostly they don't.

[ToneMerc]

Assuming the transformer is a lay down style. You remove the nuts and use them to mount the iron flush. Reinstall the factory nut

That's the best engineering practice as the lam stack is fully supported by the chassis. I would never float a heavy laydown transformer on the nuts.

TM

[M Fowler]

I'm quite sure years ago we had this discussion on TAG and it was split decision.

I have seen many amps with nuts removed but I have seen just as many with the nuts on against the chassis.

If it is better to remove the nuts then I will do that otherwise I haven't had a problem but I don't built that many lay down type amps.

[overtone]

Up until now I have been with seloutrr and ToneMerc on this one.
But... thinking about the different positions, I wondered why in many of my old 70's Brit amps I see huge Partridge transformers mounted (not lay-down) with a distance from a steel chassis. It spells trouble in the long term. If the fixings are undersized the transformers become loose and sometimes, as in this case below, the weight starts to rip the steel chassis apart.

My assumption was that this method was chosen just to take the flying leads into the chassis through a turret board, which you can see under the PT. It seems complicated, but in Britain one must drive the other way. Now I am wondering if the idea was also to keep the PT away from the chassis to prevent induction into the steel chassis too?

...time for coffee,
best, tony

[tubeswell]

Another vote for keeping the spacer nuts

[rogb]

Far from dumb, an interesting question. I would like to read some more opinions on this too.

[rdjones]

I see the logic in SO and TM's comments but every one of at least a half-dozen Fenders here have the spacer nuts.

rd

[ToneMerc]

Up until now I have been with seloutrr and ToneMerc on this one.
But... thinking about the different positions, I wondered why in many of my old 70's Brit amps I see huge Partridge transformers mounted (not lay-down) with a distance from a steel chassis. It spells trouble in the long term. If the fixings are undersized the transformers become loose and sometimes, as in this case below, the weight starts to rip the steel chassis apart.

My assumption was that this method was chosen just to take the flying leads into the chassis through a turret board, which you can see under the PT. It seems complicated, but in Britain one must drive the other way. Now I am wondering if the idea was also to keep the PT away from the chassis to prevent induction into the steel chassis too?

...time for coffee,
best, tony

Where's the washer that should be on the opposite side? Also, the "english" bracket supports the entire chassis around the cutout, only if you use it as intended. The PT that I used for my 18W Marshall clone came setup exactly like the one above that pulled through that chassis. I removed the bracket on one side and bolted it to the chassis just as Marshall did with the laydown PT models.

TM

[Reeltarded]

I leave the nuts on and add nuts.

and I am nuts.

[Cantplay]

http://www.mercurymagnetics.com/pages/c ... /index.htm

Any mounting of a heavy trafo needs a large backup stiffiner on the reverse side, and if possible triangulation to additional support.

Once an amp you build leaves your hands it will never be handled with the same care you put into it. You have to build in extra toughness against attacks. It will get bumped, dropped and mishandled.

No such thing as bullet proof, only bullet resistant.

John

[rogb]

http://www.mercurymagnetics.com/pages/c ... /index.htm

Any mounting of a heavy trafo needs a large backup stiffiner on the reverse side, and if possible triangulation to additional support.

Once an amp you build leaves your hands it will never be handled with the same care you put into it. You have to build in extra toughness against attacks. It will get bumped, dropped and mishandled.

No such thing as bullet proof, only bullet resistant.

John

Great link, thanks! I have bookmarked that page for reference, this caught my eye:

By using the two pass-through bolt channels of the transformer (instead of the standard four bolts corner bolts through the laminations) the mount reduces magnetic interference making the transformers run quieter -- ideal for recording purposes.