Jim, the filaments are wired in series in Henry amps. That explains the 10V.
Makes for a smaller wire diameter in the choke as well.
Mike Baker K7DD
K7dd@cox.net
All QSO's are uploaded to LOTW and EQSL.
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
Behalf Of Jim W7RY
Sent: Sunday, August 05, 2012 1:00 PM
To: James Durham; Amps List
Subject: Re: [Amps] Henry 2K-2 3-500 mod
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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