Replacement Circuit Board Isolation Grommets for Premier 3

The PV-1 to now...
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tzdvl
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Replacement Circuit Board Isolation Grommets for Premier 3

Post by tzdvl »

Hi, all,

I have found a perfect replacement for the aged, hardened and discolored circuit board isolation grommets in my 28-year-old Premier Three preamp!

The main circuit board in my Premier Three preamp is supported by 10 screws. The screws are isolated from the fiberglass board with soft white natural-rubber grommets.

Over the years these grommets have hardened, and have turned brown and brittle, especially on the undersides of the grommets located nearest the tubes.

I wanted to replace the grommets, but conrad-johnson no longer stocks them. I looked around for a source for replacements identical to the originals (which are made of white natural rubber), but was unsuccessful.

I decided to "kill two birds with one stone", and find a replacement as close to the originals (in size and softness) as possible, but made of silicone rubber, so they would be unaffected by heat and aging, as the originals were.

I found a source for grommets of the perfect size and hardness, and available in a pack of 25 for $6.75 (plus postage):

http://www.grainger.com/Grainger/wwg/se ... sst=subset


These 3MRP7 silicone rubber grommets are exact replacements for the originals in size and fit, and are 50-durometer hardness (I understand approximately the same "squishiness" as the originals). They are orange, rather than white, but that's OK... they will not age or be affected by heat, and they sure look better than my yellow-and-brown "crispy" originals! :mrgreen:
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Re: Replacement Circuit Board Isolation Grommets for Premier

Post by admin »

This seems like a inexpensive way to update vintage CJ gear. I have never looked inside my PV12 or Evolution 2000 amp specifically looking for this kind of issue. I wonder if this is something they used in their 90's models as well. Next time I open up any of my gear I'll take a look and perhaps due some replacements.

When you get the parts and do the replacements, could you post some pictures? I would like to know what exactly is involved with replacing these grommets before I start pulling apart my units! :)
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Main stereo: ART Amplifier and ET7s2. 2nd stereo: PV-14L and MV-55. Previously Owned: PF2 preamp, Evolution 2000 Amp, PV-12AL preamp, D/A-2b Vacuum-Tube Digital Processor.
tzdvl
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Re: Replacement Circuit Board Isolation Grommets for Premier

Post by tzdvl »

I Don't know for sure which vintage c-j components had their circuit boards mounted using rubber grommets to isolate the mounting bolts.

The only ones I know of for SURE are three of the early preamps: the PV-1 and Premier Two (black rubber grommets) and the Premier Three (white rubber grommets).

There are ten grommets in the Premier Three - you can see 'em in this photo:

Image


Neither the PV-12 or the Evolution 2000 have grommets; the boards are mounted with the bolts in direct contact with the boards.


I have already purchased my replacement grommets (from the source in my initial post), but I haven't installed them yet because I haven't had an excuse to disconnect and open up the preamp since replacing the tubes last year(above photo was taken then). Waiting for a cold snowy day this winter? ;)


The grommets will be easy to replace when I actually get around to it. If you simply remove BOTH the top and bottom covers of the preamp the mounting bolts and grommets are easily accessible.

The grommets fit neatly into holes drilled through the fiberglass circuit board, with the edges of the mounting hole fitting into the groove around the grommet so that the "flanges" of the grommet contact the top and bottom surfaces of the board.

In the Premier Three four of the grommets mount the circuit board to the side frames of the preamp, and the other six mount the board to the bottom cover with aluminum standoffs.

Image


Replace each grommet one-at-a-time by removing its mounting hardware, prying the old grommet out of the mounting hole, and then carefully "squishing" the new grommet through the hole into place.

Ken
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Re: Replacement Circuit Board Isolation Grommets for Premier 3

Post by Capt.Willard »

Thanks so much for sharing this!
I did this on my Premier Three.
It worked out well!
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Re: Replacement Circuit Board Isolation Grommets for Premier 3

Post by roberto »

Hola Chicos,

I love this thread. There are many other components that use the same grommets. A great help!

Thanks for sharing!
Happy listening!
ML CLX BF-210 Stage X Motion 4. CJ 120SE amp ET7V2 pre, Holo May Kte Dac. Mac Pro. Power Cond. BPT Signature+ 3.5, Gaia II Feet. USB Lush^V3. Nordost SPM IC and Spk. Shun Mook, BCanto CD2 CD3. Linn LP-12/Unitrack tonearm/Denon DL103R MC.
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