[Boatanchors] GB> Is 4657 same animal as the 8072?

[Carl]

All 3 versions are identical internally, the only difference being the anode 
cooler.

The 8121 was horizontally cooled and rated at 300W Pd. The only use Ive seen 
is in some industrial power supplies as a regulator. Im sure there are 
others.

For ham/military use the 8072 was used by Signal One and the 8122 by 
Hallicrafters and National. Ive seen both tubes used in many other 
commercial and industrial equipment. HP used four 8072's in a PS. A pair or 
more on a modest heat sink make a nice AM amp for real cheap money at low 
plate voltage.

Carl
KM1H


----- Original Message ----- 
From: "Mike Clarson" <mclarson at rcc.com>
To: "'Glen Zook'" <gzook at yahoo.com>; "'Sandy'" <ebjr37 at charter.net>; 
"'Glowbugs reflector'" <glowbugs at piobaire.mines.uidaho.edu>; 
<boatanchors at mailman.qth.net>; "'Scott Johnson'" <scottjohnson1 at cox.net>
Sent: Monday, October 19, 2009 1:56 AM
Subject: Re: [Boatanchors] GB> Is 4657 same animal as the 8072?


> Just some additional comments: The 4657 was supposed to be a specially
> selected 8072 for use in Motorola equipment. I have used 4657s in RCA and 
> GE
> (Did GE use this tube? I seem to remember using one is some sort of GE
> radio) radios with no problems, and 8072s in MOTRACs (Mobile and base) and
> they all operated to spec, so I suspect Motorola just didn't want to use a
> part with the name of another 2 way manufacturer.
>
> 8072 vs 4CX250 series. First, is RCA didn't design the 4CX250. Also, 8072
> was conduction cooled, and was designed to be more rugged in mobile
> applications and had a specified heater voltage of 12-15, perfect for
> mobiles. RCA also designed it to be LOW COST with a low cost socket. I
> recall buying NEW 4657s from Motorola parts, at the service shop (NSO) 
> price
> of $20 in the late 1970s.
>
> 8072/8121/8122: As far as I can tell, they are all pretty much the same 
> tube
> internally. 8072 is conduction cooled, rated for 100 watts plate 
> dissipation
> when used with simple cooling techniques. One could, with more advanced
> techniques, dissipate up to 300 watts! --According to the Tube Manual. The
> 8121 is forced air cooled and designed to run at about the 100 Watt
> dissipation level while the 8122, also forced air cooled, could dissipate
> 400 watts. RCA used one of these in their 250 watt 450 MHz base stations. 
> It
> was an odd setup where the cavity had a bunch of bi-metallic temperature
> compensation adjustments and was a real pain to tune. It would do 250 
> watts
> with a fresh tune up, but would taper off to 175 watts in about a week and
> stay there. One could retune it to 250 watts, but a week later, 175 again.
> Didn't seem to hurt the tube.
>
>
>
> -----Original Message-----
> From: boatanchors-bounces at mailman.qth.net
> [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Glen Zook
> Sent: Sunday, October 18, 2009 11:06 PM
> To: 'Sandy'; 'Glowbugs reflector'; boatanchors at mailman.qth.net; Scott
> Johnson
> Subject: Re: [Boatanchors] GB> Is 4657 same animal as the 8072?
>
> The tube is just an RCA 8072 branded with Motorola's part number.  I have
> seen hundreds of these tubes when I owned the Motorola reconditioned
> equipment center for the south-central United States.  Starting in the mid
> 1970s Motorola usually just put 8072 tubes in the boxes marked with their
> part number instead of having them specially marked.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Sun, 10/18/09, Scott Johnson <scottjohnson1 at cox.net> wrote:
>
> If a 4657 looks like an 8072, it is probably a 26 V heater variant, or
> perhaps pulse rated, or some other difference. Also these tubes are not
>> planar construction, they are coaxial.
>
>
>
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