[MD]

Couldn't one create a ring around a tube with coper wire for this
purpose? I was thinking small wire wrapped around the tube about the
size of a wedding ring?

What is the best spot on the tube (just below the getter?)

[Engineer]

MD wrote:
Couldn't one create a ring around a tube with coper wire for this
purpose? I was thinking small wire wrapped around the tube about the
size of a wedding ring?

What is the best spot on the tube (just below the getter?)

My sense is that a band of copper wire would not do much for heat
dissipation as the surface area would be hardly more than the glass
surface (there might be a bit of conduction advantage.) It might even
block or reflect back direct heat radiation from the plate, making it
run hotter. A heat sink needs fins for high surface area, one might
imagine a push-on finned shroud, but why bother. The tube is designed
to run at rated power in free air.

As for tube dampers, forget it. IMHO, this is just snake oil.
Cheers,
Roger

[Bob H.]

MD wrote:
Couldn't one create a ring around a tube with coper wire for this
purpose? I was thinking small wire wrapped around the tube about the
size of a wedding ring?

What is the best spot on the tube (just below the getter?)

I may be wrong, but I think It would probably increase internal heat
inside of the tube, since only the small edge of the diameter of the
wire would actually touch the glass, and the rest would act as an air
buffer, trapping heat inside of the the winding area. Copper wire
simply touching the glass envelope probably wouldn't be the best heat
transfer junction, as well.

Air convection around the tube should be the best way, either by
drilling holes around the base mounting for air to rise up from the
bottom across the glass face of the tube and out the top, or fans
mounted somewhere to blow air across the tube. But in a normally
vented cabinet, tubes should be ok for heat, unless they're crowded
together or something like that.

Venting slots on the top and bottorm of the cabinet should ensure air
moves through the cabinet by its self. When something is stacked on
top of a tube amp's vented area, heat damage is almost sure to follow
sooner than later.

I open up classic amps in use for most of thier lives, which have the
original tubes in them, the signal tubes covered by tube shields, and
all the tubes test strong.


Bob H.

[David R Brooks]

Engineer wrote:
MD wrote:
Couldn't one create a ring around a tube with coper wire for this
purpose? I was thinking small wire wrapped around the tube about the
size of a wedding ring?

What is the best spot on the tube (just below the getter?)

My sense is that a band of copper wire would not do much for heat
dissipation as the surface area would be hardly more than the glass
surface (there might be a bit of conduction advantage.) It might even
block or reflect back direct heat radiation from the plate, making it
run hotter. A heat sink needs fins for high surface area, one might
imagine a push-on finned shroud, but why bother. The tube is designed
to run at rated power in free air.

As for tube dampers, forget it. IMHO, this is just snake oil.

If the copper ring did succeed in extracting heat, it would necessarily
be from the small ring of glass directly under it. This would raise
stresses relative to the hotter glass either side, with a risk of
cracking. There was (still is?) a standard method of "cutting" glass
tube, by wrapping a string around, & pulling it back & forth, as though
lighting a fire with sticks. The narrow heated ring will crack easily.

[Ian Iveson]

David wrote

If the copper ring did succeed in extracting heat, it would
necessarily be from the small ring of glass directly under it. This
would raise stresses relative to the hotter glass either side, with
a risk of cracking. There was (still is?) a standard method of
"cutting" glass tube, by wrapping a string around, & pulling it back
& forth, as though lighting a fire with sticks. The narrow heated
ring will crack easily.

And if the ring is tight when hot, it will be too tight when cold.
Either the glass will break, or the copper will stretch, so it will be
too loose next time it warms up.

A constant-temperature oil circuit would be an interesting and
practical experiment, using automotive components and tin cans. We
could even save the planet by exchanging the heat with the hot water
tank. Makes valve changing a pain though.

cheers, Ian

[Bob H.]

A constant-temperature oil circuit would be an interesting and
practical experiment, using automotive components and tin cans. We
could even save the planet by exchanging the heat with the hot water
tank. Makes valve changing a pain though.

cheers, Ian

I've read about hams putting resistors in oil to get better heat
tolerance out of them. I guess a tube could be upside-down, and
inserted in oil for cooling. They could also be submerged in DI water
with a water-moving circuit like a convection cooling loop with a heat
exchanger. Xmitting tubes are sometimes cooled in DI water. Of
course, the water would have to be monitored for internal resistance to
prevent mineral content from destroying the circuit.

Seems like a lot for audio.......

Bob H.

[Chris Hornbeck]

On Tue, 10 Oct 2006 22:00:07 GMT, "Ian Iveson"
wrote:

A constant-temperature oil circuit would be an interesting and
practical experiment, using automotive components and tin cans. We
could even save the planet by exchanging the heat with the hot water
tank. Makes valve changing a pain though.

This was actually a classic in early post-War ham radio days;
a 6L6 or similar upside down in a bucket of oil. No heat
exchanger other than the bucket-to-air though.

Thanks, as always,

Chris Hornbeck

[Engineer]

Bob H. wrote:

(snip)

I open up classic amps in use for most of thier lives, which have the
original tubes in them, the signal tubes covered by tube shields, and
all the tubes test strong.


Bob H.

Fully agree. I run all my classic tube amplifiers/receivers, and any
newly constructed ones, without any cabinet. They look better that
way, too. But old radios stay in their boxes.
Cheers,
Roger

[PhattyMo]

Chris Hornbeck wrote:
On Tue, 10 Oct 2006 22:00:07 GMT, "Ian Iveson"
wrote:

A constant-temperature oil circuit would be an interesting and
practical experiment, using automotive components and tin cans. We
could even save the planet by exchanging the heat with the hot water
tank. Makes valve changing a pain though.

This was actually a classic in early post-War ham radio days;
a 6L6 or similar upside down in a bucket of oil. No heat
exchanger other than the bucket-to-air though.


I hear it was enough to crank 100+W outta one metal 6L6 though,for short
periods anyway.

Thanks, as always,

Chris Hornbeck

[Bob H.]

But old radios stay in their boxes.
Cheers,
Roger

And even in their boxes, they can be dangerous ; )

Bob H.

[Powell]

"MD" wrote

Couldn't one create a ring around a tube with coper wire for this purpose?
I was thinking small wire wrapped around the tube about the size of a
wedding ring?

How would creating a wrapping (ring of copper wire)
have enough heat dispersion surface to act as a "heat
sink"?


What is the best spot on the tube (just below the getter?)

Check out: Ensemble Tubesox damper ($89 pr) which
are make of Kevlar and copper thread. This works fine
but doesn't fit some of the unusually small based tubes
like the 6922 Mullard.

[legg]

On Sun, 08 Oct 2006 10:13:19 -0600, MD wrote:

Couldn't one create a ring around a tube with coper wire for this
purpose? I was thinking small wire wrapped around the tube about the
size of a wedding ring?

What is the best spot on the tube (just below the getter?)

Methods of cooling glass envelopes was pretty well developed in the
days they were used competently in normal design. Best to follow their
examples, if anything.

http://members.shaw.ca/legg/2000a.html

RL