Mechanical Isolation for a Power Transformer

Markhh2 · 9th December 2010, 08:13 PM

Pulling together the parts for a 300b mono amp and was wondering if it is worthwhile/desirable to mechanically isolate the power transformers from the chassis. Was thinking that felt/nylon washers may work well. Trying to limit vibrations being transmitted through chassis to the tubes. Is this an issue worth pursuing? Thanks.

Vinylsavor · 9th December 2010, 10:20 PM

Hi!

Definitely a good idea! I routinely mount power transformers on rubber isolation feet. Like the one on the pic

best regards

Thomas

boywonder · 9th December 2010, 11:34 PM

You can also get vibration isolation grommets from McMaster Carr. Drill the correct size hole in the chassis, pop it the grommet, and bolt up the transformer.

Ideally, when using these, put a washer on both sides of the grommet and a spacer sleeve in the grommet so that when you tighten the nut & bolt you don't squish the grommet. I've also used them without the sleeve spacers and they still provide more isolation than nothing.

zigzagflux · 9th December 2010, 11:53 PM

I use these from McMaster, along with standard nylon shoulder washers.
94240A110
McMaster-Carr

Provides mechanical and electrical isolation.

Wavebourn · 9th December 2010, 11:59 PM

I use thick aluminium washers. Since transformers are bolted to aluminium frame, and it is rivetted to perforated aluminium chassis, it is not a problem for a Power amp. For mic pres I use a separate PS chassis (box) in the same common box that contains 8 individual boxes for each channel.

TheGimp · 10th December 2010, 01:46 AM

Quote:

Originally Posted by Vinylsavor

Hi!

Definitely a good idea! I routinely mount power transformers on rubber isolation feet. Like the one on the pic

best regards

Thomas

Aha..ha..ha..ha.....

Harley Davidson part number 62563-65?

DF96 · 10th December 2010, 10:04 AM

I have used grommets. You just need to ensure, for safety, that the frame is grounded.

speakerfritz · 10th December 2010, 07:15 PM

isolation is a tricky buisness...partly becuase the process to tighten everything down degrades the isolation potential....a good DIY approach is to use a bolt with 2 waskers and 3 rubber faucet washers. put the tranny on 4 faucet washers that are centered on the mount holes, put one washer on the bolt, put one fucet washer next, slide the bolt/washer/faucet washer thru the hole. put a rubber faucet washer under the chassis on the bolt you side thru. put metal washer and nut. tight just enough to keep some friction while alowing the bolt to be able to be turned by hand. too tight and you loose the isolation effect. what you wind up with is rubber between the bolt head and the tranny, rubber between the tranny and the chasis, rubber between the chasis and the nut.

9th December 2010, 08:13 PM	#1
Markhh2 diyAudio Member Join Date: Dec 2010	Mechanical Isolation for a Power Transformer Pulling together the parts for a 300b mono amp and was wondering if it is worthwhile/desirable to mechanically isolate the power transformers from the chassis. Was thinking that felt/nylon washers may work well. Trying to limit vibrations being transmitted through chassis to the tubes. Is this an issue worth pursuing? Thanks.

9th December 2010, 11:59 PM	#5
Wavebourn diyAudio Member Join Date: Sep 2006 Location: Pleasant Hill, CA	I use thick aluminium washers. Since transformers are bolted to aluminium frame, and it is rivetted to perforated aluminium chassis, it is not a problem for a Power amp. For mic pres I use a separate PS chassis (box) in the same common box that contains 8 individual boxes for each channel. __________________ If I disappear suddenly, that means I finally created a time machine and pushed wrong button that brought me to Stalin's Russia. In any experiment any result is the result. Even if it is negative.

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9th December 2010, 11:34 PM	#3
boywonder diyAudio Member Join Date: Jan 2008 Location: So.Cal.	You can also get vibration isolation grommets from McMaster Carr. Drill the correct size hole in the chassis, pop it the grommet, and bolt up the transformer. Ideally, when using these, put a washer on both sides of the grommet and a spacer sleeve in the grommet so that when you tighten the nut & bolt you don't squish the grommet. I've also used them without the sleeve spacers and they still provide more isolation than nothing.

9th December 2010, 11:53 PM	#4
zigzagflux diyAudio Member Join Date: Oct 2006	I use these from McMaster, along with standard nylon shoulder washers. 94240A110 McMaster-Carr Provides mechanical and electrical isolation.

10th December 2010, 10:04 AM	#7
DF96 diyAudio Member Join Date: May 2007	I have used grommets. You just need to ensure, for safety, that the frame is grounded.

10th December 2010, 07:15 PM	#8
speakerfritz diyAudio Member Join Date: Jul 2008	isolation is a tricky buisness...partly becuase the process to tighten everything down degrades the isolation potential....a good DIY approach is to use a bolt with 2 waskers and 3 rubber faucet washers. put the tranny on 4 faucet washers that are centered on the mount holes, put one washer on the bolt, put one fucet washer next, slide the bolt/washer/faucet washer thru the hole. put a rubber faucet washer under the chassis on the bolt you side thru. put metal washer and nut. tight just enough to keep some friction while alowing the bolt to be able to be turned by hand. too tight and you loose the isolation effect. what you wind up with is rubber between the bolt head and the tranny, rubber between the tranny and the chasis, rubber between the chasis and the nut.