Is a chassis bracket necessary

[lmolter]

I'm wondering if a chassis bracket is necessary for my 5F6A chassis. The transformers are large and heavy, and I could see the need to take some of the strain off of the chassis mounting bolts. Any thoughts here? Anybody use a different form of bracing for heavy chassis (what's the plural of chassis?)?

And while we're on chassis mounting (and this may be a dumb question, but this is my first build with no previous amp-building experience)... are the chassis mounting screws just #10 or so bolts that pass through the chassis holes with the nuts and washers mounted inside the chassis, or is there some style of captive nut used. I ask this because a Peavey Classic 20 I took apart had black doodads (for lack of a better term) that the long woodscrew-like screws went into. The screws were not bolts but rather like wood screws. Of course, that chassis wasn't very heavy. The OT was the size of a golf ball and the PT might have been 3" square (not even). Quite a difference from the MM iron in my Bassman.

I feel funny asking obvious questions, but... I don't really know how the chassis is mounted.

Larry

[Daver]

Absolutely use some type of bracket. There's too much weight pulling on just the two bolts. I use 10-32 truss head screws to mount tweed style chassis. The head is a little larger that a standard machine screw. Use a fender washer and a locking nut or lock washer to fasten.
You could make your own bracket if you're handy with tools. I've seen people use an L shaped angle bracket screwed to the side of the cabinet with padding on top and letting the PT rest on it. It sort of makes a shelf for the PT to lay on. The cleanest, easiest route would be to get one of Bruce's chassis brackets made specifically for tweed chassis. http://www.missionamps.com/hardware.shtml
Good luck!

Dave

[lmolter]

Daver, I also thought about using angle bracket for a support. Glad someone else already uses it.

In regards to the Mission Amps bracket - I'm hesitant to drill holes in a completed chassis. What about shavings getting into the wiring? I guess if I'm careful, I could try it. Do I need two brackets? Mission's website suggests only one is needed (at least it appears that way).

L

[tubeswell]

Daver, I also thought about using angle bracket for a support. Glad someone else already uses it.

In regards to the Mission Amps bracket - I'm hesitant to drill holes in a completed chassis. What about shavings getting into the wiring? I guess if I'm careful, I could try it. Do I need two brackets? Mission's website suggests only one is needed (at least it appears that way).

L

Keep your vacuum cleaner handy when you're drilling the holes. Any old decent quality L -brackets of the right dimensions from a hardware store will do the job

[Daver]

Larry,
I'm with tubeswell on this. A shop vac along with some upside down chassis shaking exercise should work out fine. I've added holes to completed chassis for ground lugs, etc. with no ill effects.
Dave

[lmolter]

okey-dokey. I've got the Mission brackets on order as we speak. Thanks again to everyone.

[Enzo]

For reference, those are sheet metal screws, not wood screws. They look similar but are not the same.

The little flat clip on things that serve as nuts are called tinnerman's nuts, and some call them speed nuts.

The ones like larger amps use that have an actuall threaded square nut that snaps into a little housing that in turn snaps into a square hole in the chassis is called a cage nut or caged nut. Machione screws turn into those.

Some people may have other terms for those as well.


One alternative would be a wooden cleat on the side wall of the cab for the tranny to rest on. A few inches of 1x1 would do fine. Can't think of who right off, but I've seen that in commercial amps.

A chassis stiffening plate under the things is something else to think of.

[Bruce / Mission Amps]

Daver, I also thought about using angle bracket for a support. Glad someone else already uses it.

In regards to the Mission Amps bracket - I'm hesitant to drill holes in a completed chassis. What about shavings getting into the wiring? I guess if I'm careful, I could try it. Do I need two brackets? Mission's website suggests only one is needed (at least it appears that way).

L

Sorry I didn't get a chance to respond until now, just got back from a 9 day trip.
Right, only one L bracket is needed for a tweed 6L6 amp of this size.

The heavy duty bracket I sell/use in my tweed 6L6 amps (and the 6L6 Aurora amps) is drilled for four 8-32 screws and nuts to hold it to the chassis.
This is SUPER solid, but you can use two if you are worried about the debris that could fall into the chassis.
Of course make sure the amp is not plugged in and the tubes are all out of their sockets when you do this.
I put a loose piece of duct tape on the inside of the chassis and drill into it from the outside to catch as much as I can.
A little magnet will grab the rest if you can drag it around in there.

[Bruce / Mission Amps]

...Any old decent quality L -brackets of the right dimensions from a hardware store will do the job

Well, not really quite true... the bell cover of the power transformer will get in the way of mounting it.
With respect to a generic L bracket, you have to grind off or file off a large part of the corner to get them to fit the PT. Plus, you'll probably find drilling the hole larger or in slightly different place on one end is needed... and don't forget, you have to remove the sealed screw/bolt from the PT laminations to mount them.
Those are the reasons I gave up on using simple L brackets on these heavier PTs with tweed style chassis and came up with the big brace bracket mounted to the outside of the chassis instead.

[lmolter]

Thanks, Bruce. I got them today. I say 'them' because I ordered 2 thinking I would place one on each side for more stability. D'oh! The brackets are bent to fit on one side only. Dolt (me, not you). They can't be flipped. Doofus (same). I guess I'll have to build another tweed somethingorother (if I can ever get rid of that danged hum). See my other threads.

Oh, the ravages of old age.

[Bruce / Mission Amps]

Thanks, Bruce. I got them today. I say 'them' because I ordered 2 thinking I would place one on each side for more stability. D'oh! The brackets are bent to fit on one side only. Dolt (me, not you). They can't be flipped. Doofus (same). I guess I'll have to build another tweed somethingorother (if I can ever get rid of that danged hum). See my other threads.

Oh, the ravages of old age.

Oops... just send one kit back the cheapest way possible and I'll refund your purchase price.

[lmolter]

Thanks, Bruce, but I'll keep it if I can use it on a 5E3 chassis.

L

[Borg54]

For drilling holes in an amp, I have always used a shop vac with the smallest adapter and placed this on the inside over the perspective hole. The suction holds it in place pretty good. Then on the side that I am drilling from I use the ring magnets out of an old microwave, just place a strip of clear packing tape over the outside and you can see where you are drilling and the tape and magnet will catch most of the fallout. I then remove the magnet first then the shop vac. Works every time.

The size of microwave mags. even allows for some of the larger sized stepped drills for tube holes (drill mounting holes 1st). Good thing that’s my vacuum cleaner instead of the wife’s.