Mounting transformers, capacitors, etc. to bottom of chassis

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How does one mount large PSU capacitors (wired via point-to-point wiring) to the bottom of a rackmount chassis? Does it need to be mounted at all, or can it be free-floating if there aren't other components around to be harmed? Would a lot of hot glue be sufficient? :p

And this one's been bugging me... when people mount transformers and board standoffs to the bottom of their chasses, do they have the screw heads sticking out from the bottom? Usually when people post pictures of their amps and preamps with toroids and boards on standoffs, they never take pictures of the bottom of the chassis (not like it's important). Since I'll be ordering some kind of rackmount chassis, it might not come with feet. I'll be using Vibrapods not permanently attached for the chassis, but in case I need to move the chassis to a table temporarily, I'd rather not have anything sticking out of the bottom to scratch up the table. Any ideas or recommendations for a guy with a limited toolset?

Thanks,
Greg
 
Hi Greg

I use large diameter cable ties to mount PS capacitors. You drill two holes in the chassis base, one either side of the capacitor, and thread the tie through, drawing the capacitor down under it. I think its best to place a sheet of insulating material between the caps and the metal chassis when using this method - the plastic sheath on the caps may be punctured. I used a piece of scrap veroboard for this.

Unless your case has a separate internal chassis, screw heads will indeed protrude underneath the finished unit. I don't mind this since no one ever really sees underneath, and I use a set of self adhesive feet to provide a standoff, preventing the bolt heads scratching my furniture.

Hope this helps you,
Tim.
 
I like to glue the capacitors to fiberglass board or plexiglass with silicone. Hot glue is not recommended because of heat. This provides both easy way to mount the caps as well as damping. But my caps are usually on a smaller side. I wouldn't be worried about the screws on a bottom panel. But if you want to avoid too many screw heads on display, you can make subchassis, mount everything to it and then with 4 or 6 screws mount the subchassis panel to the bottom of your amp.

http://www.diyaudio.com/forums/showthread.php?s=&threadid=5980&pagenumber=3
 
Here's an alternative solution.

Some think outside the box, and others think outside the tube. :)

<center>
<img src="http://www.q-audio.com/images/flatpack.jpg">
</center>

Not only are they small (1.5 x 3 inches or 1.5 x 1.5 inches) and flat (just 1/2 inch) but they have integrated moutning. <a href="http://www.mouser.com">Mouser</a> sells a decent selection of them.

Just be aware that the case is tied to the negative lead so be careful there. I'd recommend nylon hardware.

se
 
I used plexiglas for a "sub chassis panel"

Went to a sign shop and they gave me some free out of their scrap bin.

Glued stuff to the plexiglass - then held the plexiglass to the chassis from the top side with transformer and tube socket nuts.

Cheap, non-conducting, easy to work - do tight work outside the chassis and then slip it in as a module.

:Popworm:

Ken L
 
Yeah, but aren't those caps more expensive than than my first car Steve? ^_^

To solve the chassis-on-table dilemma you could add some cheap, low-profile rubber feet that are tall enough to protect your table. Just mount them out of the way of your pods, and then you can take your pick without limiting your construction options.
 
Thanks for all of the suggestions.

I may try that sub chassis panel idea, not necessarily with plexiglass or fiberglass (maybe something easier for me to work with :p), and then bolt that panel to the chassis.

As for the underside of the chassis, I might as well just screw in the Vibrapods permanently using the same screw/nuts holding on the transformers (I got that idea from Peter's thread where it was discussed to put on feet with the same screws used to mount the internal assembly's standoffs) - I'm making a dual mono Leach amp, with the tentative layout being one transformer at each side in the front. Most of the weight comes from the transformers and heatsinks anyway, so I think this should be ok. I'll place a 3rd Vibrapod in the back of the chassis in the middle, with a screw.

-Greg
 
This is the stuff! Smells not too good I must add, rather unhealthy.
 

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IMHO, I would not use any plexiglass inside an electrical enclosure. I think they tend to build up/gather much static charge, even though I got my plexiglass experience from building my own wet dry filter for my 100 gallon fish tank, the static on the plexiglass is very strong and attrack lots of dust after you rub it accidentally when working with them.
Just my 2 cents.
 
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