• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Chassis tube holes rubber grommet/washer

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#21
PKI said:
I know it is a weird question. Do you know what is the name for those rubber grommet rings they put on the tube holes in the chassis? Trying to find, but for some reason fail to do so. Would appreciate it you can point me in the right direction.
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I found a good selection pack at the local builders merchants of all places, so if you're at a merchant check the electronics section. Easier to mail order though.

Personally I wouldn't use them around a tube specifically due to radiated heat. Where I would use them is cabling and specialist dampening grommets for suspending metal plates holding sensitive microphonic tubes (for photo etc).
 
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#24
Philwait said:
These ones fit 9-pin tubes such as (12AX7 etc.) - KEYSTONE 8480 - Digikey part 36-8480-ND

These ones fit 8-pin octals (EL34 etc.) - KEYSTONE 8484 - Digikey part 36-8484-ND

Expect to pay less than $1 each. You can see then used in the 5W amplifier kit at DIY Valve Amplifier kitset

Hope that helps.... Phil
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Do we know what kind of heat these can tolerate? They look nice!
 
#25
Philwait said:
These ones fit 9-pin tubes such as (12AX7 etc.) - KEYSTONE 8480 - Digikey part 36-8480-ND

These ones fit 8-pin octals (EL34 etc.) - KEYSTONE 8484 - Digikey part 36-8484-ND

Expect to pay less than $1 each. You can see then used in the 5W amplifier kit at DIY Valve Amplifier kitset

Hope that helps.... Phil
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The Nylon 6/6 these are made of is rated for 210deg F. Will that survive near a tube? I guess it would at the base but not sure about chassis holes for example part way up the envelope. Or would it?
 
#26
You also have to look at long term degradation.
Plastic bags left in the car in sunlight will disintegrate within weeks.
Keeping stuff near hot tubes will reduce its life.
Change the design, your tubes will also fail early.
Unless you are building a shelf queen for show.
 
#27
NareshBrd said:
You also have to look at long term degradation.
Plastic bags left in the car in sunlight will disintegrate within weeks.
Keeping stuff near hot tubes will reduce its life.
Change the design, your tubes will also fail early.
Unless you are building a shelf queen for show.
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Don't be negative! haha 🙂 I see your point and aware of temperature impact on plastics. This is my Aikdo preamp I am planing to box. Tubes are not that hot in that one, but I will still try to make it as clean as possible with just the holes and will keep the plastic stuff as a plan B. So I do appreciate the discussion.
 
#28
PKI said:
Don't be negative! haha 🙂 I see your point and aware of temperature impact on plastics. This is my Aikdo preamp I am planing to box. Tubes are not that hot in that one, but I will still try to make it as clean as possible with just the holes and will keep the plastic stuff as a plan B. So I do appreciate the discussion.
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I hope I didn't come across as rude! I'm seriously interested in this, especially like you said for a preamp where the tube halfway come through the top. My phono-stage looks like this and a plastic or metal trim ring on the hole would dress it up.
 

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#29
NareshBrd said:
You also have to look at long term degradation.
Plastic bags left in the car in sunlight will disintegrate within weeks.
Keeping stuff near hot tubes will reduce its life.
Change the design, your tubes will also fail early.
Unless you are building a shelf queen for show.
Click to expand...

You could look a silicon grommets or even PTFE (they'd take the heat better).

Nothing wrong with making a good looking amp 😀
 
#31
Steve Morley said:
I've used a Starrett hole saws a little undersized then a Dremel to get the final size for the bushing.
Mouser has them in many sizes. Search number 836-2182 for instance. Go oversized 1/8" all around (1/4" larger diameter) for small tubes, perhaps larger for power tubes.

S.
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Good suggestion.

I commercially make Guitar amps, 99% of them SS because that puts the meat on the table, so equipped accordingly including shears, benders, punchers to make chassis of any kind and shape, but now and then some customer insists on tubes.
Oh well.

Up to Noval sockets, I can punch them out , with my XLR socket punch, go figure.
Slightly oversized but no big deal, and hole is perfect, clean edges, the works.

But then I need larger holes for octal sockets.

Lo and behold, Starret cup saws come to the rescue.

Holding them in a solid stable vertical drill press is one part, firmly *clamping* the aluminum sheet/chassis is the other, hole is cut reasonably smooth , and I made a hand tool to deburr edges, result is incredibly good.

No customer ever complained or even noticed that hole was not punched in a large mechanical press.

Punched / drilled before bending (still flat sheet aluminum):
729640500_9294c16fcd_z.jpg


bent and assembled:
730236838_4fbdc30b12_z.jpg


mounted on 4 x 10" cabinet:
730236896_59d57efee7_z.jpg


a lot of minor sins are forgiven, actually ignored, because hole is not alone, floating in space to be admired or criticized, but as part of a larger complex object.
 
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