[Central-Electronics] CE 200V - Tubes

Wed, 18 Feb 2004 06:27:58 -0600

	Chuck,

	I am enjoying this thread about tubes immensely. You mention going to a
lower power output tube to better match the low drive needs of the 600L. A
6-10 DB pad is not a bad way to go since no rig mod's are necessary.

	I am working on a 20A QRO project (#3) and since adding a neutralizing
circuit, I can try all sorts of tubes. Last night I shoe - horned a single
6550 into the 20a! Think of the hemi under glass 1964 Plymouth Barracuda. A
tight fit, but it went like a heck. Anyway, I have found only two tubes that
provided wonderful linearity, with high power sensitivity in my 20A projects
(the 6AG7 was not one of them). Those are the 7591, and the 6550. The 7591
(also comes in Novar as 7868, and 9 pin as 6GM5) is in a similar class as
the 6550 with ratings reduced about 50%, and is the same size as a 6V6. It
does however have a different base pinout (sigh), but makes up for that with
two G2 socket connections. There is a 6 meter AM rig using a 7868 to drive a
7984, so the 7591/7868 are good RF tubes with VERY low interelectrode
capacitance. The 6GM5 may be good too, but only one socket connection for
G2. I have never tried the new production 7591-EH (in a bulb the size of a
6L6GC), and the old NOS 7591's are pricey. You can get the 7591's on Ebay as
part of a amplifier sometimes cheaper than the tubes by themselves. Look for
a dirty, and non working Sansui 1000a AM/FM 50 watts RMS / channel tube amp
as they have 4 of them inside (not the Sansui 1000).

	I wonder about a simple mod to the 100v where the 6550 Plate B+ comes from
the LV B+ instead of the HV B+. If you try this, make sure the tube is
biased right, and if so, it should work very well at a reduced power output.
Just a thought for you 100v/200v gents to ponder.

Regards,
Jim Candela
WD5JKO

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Chuck
Ochs
Sent: Tuesday, February 17, 2004 7:18 PM
To: [email protected]; 'Radio Central Electronics'
Subject: Re: [Central-Electronics] CE 200V - Tubes


Hello George--
Gross generalizations here, but the Russian tubes are vastly superior to the
Chinese variety. I expect that in a few years, the opposite will be true, as
the Chinese clean up their quality control problems.
You are right to mention that using a 100-V or 200-V with 6550s is serious
overkill, when driving the 600-L.
I haven't had a chance to experiment yet, but the idea of going to a less
powerful (and less expensive) tube, such as the 6L6 / 5881, or even the 6V6,
has occured to me. This may result in identical overall operation with
vastly lower tube cost. Has anyone on the list tried this? I have
successfully employed this technique with audio power amplifiers.
Chuck N1LNH
----- Original Message -----
From: "George Maier" <[email protected]>
To: "'Radio Central Electronics'" <[email protected]>
Sent: Tuesday, February 17, 2004 9:47 AM
Subject: RE: [Central-Electronics] CE 200V - Tubes


> Thanks Chuck - your advice is both sage and sensible, and I'm sure that we
> all agree that Tung-Sol is the best.
>
> I guess my question deals more with how the others (Sovtek, Svetlana,
Valve
> Art, Winged C, etc) actually perform, and what is different about them.
>
> If the RF o/p is not as high, but the linearity is the same, some people
> might not care.  For example, when driving a 600L, a 100V/200V is total
> overkill, and the exciter power control is at or close to minimum anyway.
> Also, if you run barefoot and get 80W instead of 100W, that's less than
1.0
> dB, and no one would ever notice.  In my case, I typically drive a
3-1000Z,
> which takes most of what the 200V can put out, but there's still some room
> to spare.
>
> If on the other hand, the other-than-Tung-Sol tubes do not exhibit good
> linearity, or don't last very long, that's quite another matter.
>
> Any comments (from anyone) will be appreciated.
>
> 73,  George - K1GXT
>
>
>
>
>
> -----Original Message-----
> From: Chuck Ochs [mailto:[email protected]]
> Sent: Tuesday, February 17, 2004 1:49 AM
> To: [email protected]; 'Bill Marx'; 'Radio Central Electronics'
> Subject: Re: [Central-Electronics] CE 200V
>
> 6550 tubes--
> The best ones ever made were the Tung-Sol variety. Highly sought after for
> audio amplifiers also. The currently available types pale in comparison.
> Chuck N1LNH
> ----- Original Message -----
> From: "George Maier" <[email protected]>
> To: "'Bill Marx'" <[email protected]>; "'Radio Central Electronics'"
> <[email protected]>
> Sent: Monday, February 16, 2004 9:04 PM
> Subject: RE: [Central-Electronics] CE 200V
>
>
> > Looks like mine did when I first got it.
> > Speaking of the "V", has anyone on the list taken the time to evaluate
the
> > various types of 6550's that are around these days?  Prices are all over
> the
> > place, but I've been wondering what's good and what's not.
> > Thanks & best to all,
> > George - K1GXT
> >  *** CE is all you need - period !!! ***
> >
> >
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]] On Behalf Of Bill
Marx
> > Sent: Monday, February 16, 2004 5:31 PM
> > To: Radio Central Electronics
> > Subject: [Central-Electronics] CE 200V
> >
> > This list has been quiet of late. Here is a 200V to get everyone
excited.
> >
>
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4675&item=3078714415
> >
> > -Bill W2CQ
> > _______________________________________________
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> >
> >
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