Date: Wed, 13 Jul 2011 13:27:35 +0100
From: "Dr. David Kirkby" <david.kirkby@onetel.net>
Subject: Re: [Amps] Who sells 3CPX-800A7's besides RF parts ??
On 07/13/11 11:01 AM, Jim Thomson wrote:
> I use to know this..but lost the info. There was a couple of co's
> somewhere in the eastern usa that had... 'good' prices on 3CPX-800A7's.
>
> Tnx... Jim VE7RF
Do you need the pulsed version (P in the part number)? The 3CX800A7 is far more
common than the 3CPX800A7. Without looking at the data sheets, I've no idea how
similar they are.
There are tons of 3CX800A7s on eBay.
## An associate of mine wanted the pulse rated version,and NOT the more common
version.
The pulsed version was good for something like 3500 vdc. Years ago, eimac
sent out a bulletin, and advised broadcaster's etc to use the
pulse version for these low power 750/1500 output 1 and 2 tube FM
broadcast TX's. The line v in some parts of the world is not good, plus
toss in transients/spikes, gen sets at times etc... and way too many failures.
The pulse rated versions drop right in.. and now u have some V
head room = no more failures.
I think my ham friend wanted some extra v headroom, cuz perhaps his B+ supply
was a bit on the higher side for the standard version..and he doesn't
want to push his luck. Some other folks have plugged the pulse version into
their Alpha 87-A's..and they run just fine..albeit with abt 10 ma more grid
current, that's it.
I don't think the pulsed version was that much more $$ either. In the case of
broadcaster's, that's nickle and dime stuff anyway. They just want
reliability. BTW, our fed govt has a forestry dept here in town, where
they use a 3CX-3000A7 to generate RF at 70 mhz... then radiate it into plants
etc, that have been subjected to various gas's.. [think they used argon, among
other's]... then the result is it breaks it into the colour spectrum for a
given species. Some kinda
spectrograph if I remember correctly. The kicker was, they used a
5000 VA rated eq of a big Sola constant v xfmr.. to provide regulated AC to
the plate xfmr of the b+ supply. That was a new one on me.
[ Eimac 3x3 tube got replaced with a SS PA module.]
Impractical for broadcasters. The pulse version is cheaper solution.
later...... Jim VE7RF
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