[Amps] Henry 2K-2 3-500 mod

[R. Morris]

They are talking about a 10 volt zener, not filaments....

On 08/05/2012 04:54 PM, Mike Baker wrote:
> 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 at cox.net
> All QSO's are uploaded to LOTW and EQSL.
>
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at 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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