So how much room is between the top of the cabinet and the plate cap? What
about a lower profile plate cap? Are you trying to use the same chimneys?
I've heard of others running 3-500s in older henry amps with no issues
except for lowering the tubes just enough to get the clearance needed to the
top of the cabinet.
10 volts is a bit high for 3-500s. 5.1 or 6.8 volts would be better. 10
volts is fine as long as you don't ever run it on SSB.
73
Jim W7RY
-----Original Message-----
From: James Durham
Sent: Sunday, August 05, 2012 10:45 AM
To: Amps List
Subject: [Amps] Henry 2K-2 3-500 mod
I'm looking for some info from someone who has actually done the mod to put
3-500's in a Henry 2k-2.
My 3-400s finally bit the dust after years of service and its time to think
about
putting 3-500s in there.
My understanding was that all that was involved was lowering the sockets to
accomodate the greater height of the 3-500's. I did this. Now, the glass
envelope
of the tubes nearly fill the round holes in the chassis where the air comes
through.
So, I'm wondering if part of the mod involved making those holes larger?
Also, just as a curiosity, my amp is definitely a 2k-2 , however it has the
zener
mod for bias and the plate circuit protective fuse. 2k-2's are not supposed
to
have those. I've had this amp for about 8 years, but never really
investigated
to see what the deal is with that. My buddy suggested that maybe it was an
'end of model' production and is sort of a 2k 2 1/2 ? So, I thought, maybe
somebody
already did the mods, but the zener, etc, look to be a factory installation,
but, in that
case, why is it not set up for 3-500s already? Also, although the 10volt
zener was
in there, I did not have the correct manual until recently (I had a 2k-3
manual) and
I didn' t realize that the zener was not supposed to be there. Amp worked
fine.
No reason to investigate. Probably the IMD was higher than it should have
been
with 10 volts bias on 3-400's, but I'm mostly a CW dude, so I didn't notice
that.
Anyway, any insight appreciated. I sure would hate to have to dismantle
everything
to cut those holes larger.If that's what has to be done, I'd like to hear
how others
did it. I guess you could use a nibbler (Ugh!) or patch in a piece of metal,
drill a
center hole and use a fly cutter.
I did the checking of the clearances with my old 3-400's, but they are only
slightly
bigger in diameter, so I think that was a valid test.
Thanks,
Jim, W2XO
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