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Old 9th December 2010, 09:13 PM   #1
Markhh2 is offline Markhh2  United States
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Default 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.
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Old 9th December 2010, 11:20 PM   #2
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Definitely a good idea! I routinely mount power transformers on rubber isolation feet. Like the one on the pic

best regards

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Old 10th December 2010, 12:34 AM   #3
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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.
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Old 10th December 2010, 12:53 AM   #4
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I use these from McMaster, along with standard nylon shoulder washers.

Provides mechanical and electrical isolation.
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Old 10th December 2010, 12:59 AM   #5
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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.
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Old 10th December 2010, 02:46 AM   #6
TheGimp is online now TheGimp  United States
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Originally Posted by Vinylsavor View Post

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

best regards


Harley Davidson part number 62563-65?
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Old 10th December 2010, 11:04 AM   #7
DF96 is offline DF96  England
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I have used grommets. You just need to ensure, for safety, that the frame is grounded.
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Old 10th December 2010, 08:15 PM   #8
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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.
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