Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: joesatch on June 15, 2025, 01:50:36 pm
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how close is too close? i know caps dont like heat
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how close is too close?
can u smell that smell :icon_biggrin:
if you have another inch to spare, i'd use it.
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i dont. this is the chassis. not punching another hole this is a flimsy aluminum chassis
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how close is too close? ...
... not punching another hole ...
Seems like the answer doesn't matter.
I suppose you could try to fit a heat-shield between the tube & the can as Hiwatt did in their amps.
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i might go with a small radial cap rated 105 degrees with an adapter plate and shield it as well.
(https://media3.giphy.com/media/v1.Y2lkPTc5MGI3NjExcnFmYjliY3JibmR6d2JqcTFyYXdybXlhYzhscjhtMXFjNWtub21kcCZlcD12MV9pbnRlcm5hbF9naWZfYnlfaWQmY3Q9Zw/TY3bikeN6R4DS2wpcN/giphy.gif)
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Is there much space to have it mounted sideways on the inside, then you only have to drill 2 holes for the clamp mounts
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Push it down into chassis
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Is there much space to have it mounted sideways on the inside
The HiFi snoots do this all the time. Works great, especially in this situation. Electrolytic caps are heat sensitive -- they tend to dry out. You can get some rated for higher temps, but they are still heat sensitive IMO.
Proper film caps are less prone to heat damage, the ones designed for electric motors. If your caps are not more than 40uF, you can use those with impunity, though they are most definitely larger than modern electrolytics.
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If HiFi snoots do this, maybe just try it.
If it creates a problem then move caps inside
leaving the unconnected can on top for "looks" and hole fill.
I have also read that the tube might have a "cooler" side that you might face toward the can.
BTW - for my info, what would be the result if too much heat on the cap? would it short after it dries out?
If so maybe a secondary fuse might protect the PT assuming that would be at risk.
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+1 to move to inside chassis. Use the can mounting holes for a pair of terminal strips and strap in a 500V radial.
I have used these (https://www.mouser.com/ProductDetail/Rubycon/500LXW100MEFR18X45?qs=T3oQrply3y9cgWWEelW2Xw%3D%3D) in the past.
--Pete
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or my info, what would be the result if too much heat on the cap? would it short after it dries out?
The electrolyte within the cap evaporates, leading to decreased capacitance and increased ESR -- basically what you normally see when you're re-capping an old amp. Shorts can occur, but much less common.
Those Rubycon's are excellent, but they also have models that are rated to 125C. Very robust.
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If you go inside,
I often use radial caps on a terminal strip with the resistors across the terminals.
Pic from Goldeluxe below
https://stillampd.com/goldeluxe-03
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Standard on JTM45 builds.
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I had to mount a cap can inside one of my amps, and had an issue because if I added screws coming from the side of the chassis, they would interfere with inserting the chassis into the cabinet, as it is a tight fight like Fender blackface amps. Solved it by making an L bracket that attached to the chassis floor and attaching the mounting clamp to the upright piece.
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project scrapped for now. no room to mount the caps inside. i ordered a new chassis