Bear (?), I've had lots of Henry 3-500Z amps over many years, and they do
use a pressurized chassis and chimneys, just like Eimac used to say to
do...but the tubes didn't run cooler as a result (notwithstanding the
filament voltage problems!), they ran hotter than in similar amps using the
axial above-and-below deck cooling a la SB-220 and Ameritron.
I'm guessing:
-The actual air flow around the glass using high-volume, low-pressure
(axial) cooling is better than using low-volume, high-pressure (blower with
chimneys) cooling, resulting in more efficient thermal exchange;
-The already-heated air (heated by underchassis components and the filament
pins) blowing up around the envelopes is substantially hotter to begin with
than the ambient air blown past the envelopes when high-volume axial cooling
is used;
-The critical and well-selected spacing of the axial fan to the tube
envelopes results in about equal cooling of the entire envelopes, including
the surface opposite the side with the air applied -- kind of clever.
While it's really hard to compare "my tubes lasted longer than your tubes"
stories due to variations in filament voltage, cooling, how hard the tubes
were really used and also the manufacturer and even manufacturing lot of the
tubes themselves, I'd have to say I've had 3-500Zs last in the "SB-220
cooling method" amps every bit as long as, or longer than, the "forced air
with chimney method" amps like the Henrys, and in most cases that was more
than 10 years of frequent use -- after which time, the tubes are pretty much
"free," aren't they?
WB2WIK/6
"If everything seems under control, you're just not going fast enough." -
Mario Andretti
> -----Original Message-----
> From: BEAR [SMTP:bearlabs@netzero.net]
> Sent: Tuesday, December 03, 2002 10:49 AM
> To: amps@contesting.com
> Cc: Rich
> Subject: Re: [Amps] Q: Chimneys for 3-500/4-400??
>
> Rich wrote:
>
> > The work-around is to plagiarize the split-chassis transverse 6" fan
> > cooling system used in the Heath SB-220. The glass envelopes will run
> > way cooler, the amp will run quieter, and there will be no expensive
> > glass chimneys to buy.
>
> Nah nah... no thanks... I think the issue is the temperature of the plate
> seal
> and the pins seals... I'd also prefer to have the same temp air on all
> sides of the tube.
>
> You should read the description of how HOT the Henry folks intend to run
> these
> tubes - *very*.
>
> I've got a nice quiet "squirrel cage" fan for the bottom... expect it do
> do
> way better than a muffin fan blowing across ... unless I'm missing
> something
> about the Heathkit method?
>
> I'm going PICKLE style! :- )
>
> _-_-bear WB2GCR
>
> >
> >
> > >
> > >Wondering if anyone can suggest an inexpensive source for chimneys for
> > >the 3-400/4-400 type tubes? Especially cheap imports. :- )
> > >
> > >Or if anyone in the US has a pair they want to blow out...
> > >
> > >Or if anyone has a DIY solution...
> > >
> > > _-_-bear
> > >
> > >
> > >
> > >--
> > > _-_-bearlabs
> > >
> > > http://www.bearlabsUSA.com
> > > - Silver Lightning Interconnects & Custom Mods -
> > >
> > >
> > >_______________________________________________
> > >Amps mailing list
> > >Amps@contesting.com
> > >http://lists.contesting.com/mailman/listinfo/amps
> > >
> >
> > - Rich..., 805.386.3734, www.vcnet.com/measures.
>
>
>
>
> --
> _-_-bearlabs
>
> http://www.bearlabsUSA.com
> - Silver Lightning Interconnects & Custom Mods -
>
>
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