[Amps] [ham_amplifiers] Sweep Tube Amp

Thu Nov 26 08:50:53 PST 2009

Toll Free wrote:
>  
> 
> David,
> 
> Are you getting a 'blue glow' from the tubes on key down RF output? 
> Voltages all OK?
> 
> The 6LQ6 6JE6C AND 6MJ6 are interchangeable. The 6MJ6 actually HAS an RF 
> rated tube version. It is easily found out by having two plate 
> connections, and the anode structure is BLACK, and the anode cap is as 
> well. Problem with them is this: Mucho Cout and Cin compared to the 
> other tubes. Easily tuned out by adding slight amounts of L to the anode 
> lead of each tube.
> 
> Oh yeah.. What are you DRIVING it with? Those amps had a LOT to be 
> desired in the tuned input department... As a 'test', I rebuilt a 1x2 
> amp, 12JB6 into pair of 8950s. Stock, carrier level was about 25 watts, 
> MAX! Pulled the drive tube, built a tuned input for it, it now makes 400 
> PEP 9driven to saturation), with the same radio as driver before. You 
> MIGHT be getting swr foldback... Another example is my SB220 on 11 
> meters... The TS440SAT will foldback HARD on mod peaks, netting me about 
> 400 watts PEP, MAX. I turn on the tuna in the radio, 1200 pep. So, if 
> you are using a solid state exciter, I'd look at input match FIRST! 
> Most, if not all, of the multi sweep tube amps had little to NO input 
> network, designed around and to be used with tubed exciters that can 
> provide the necessary Q needed to keep the newer exciters happy.

I am driving it with a SBE-33 which is the companion transceiver that
this amp was designed for.  It solid state except for the driver and
finals, a pair PL-500's.  It will put out close to specified output into
a 50 ohm dummy load.  The input of the amp is untuned, a bank of
resistors, and operates AB1.  Over the weekend I will do more investigating.

The amp has output and plate current meters.  When I was getting 1.2 mA
on the plate current, the output meter was reading very low.  This is
what I would expect when the inline watt meter was reading only 150W.  I
am using my Collins 312B-4 speaker/watt meter to measure output.
Unfortunately a 250W slug is the largest one I have for my Bird 43.  I
am going to put the Bird between the transceiver and amp to check input.

BTW this is not a CB amp.  It was designed for ham bands.  I was trying
to tune it at 14.25 MHz.
> 
> One thing that DOES make me fear your tubes is that you CAN get plate 
> current right up there, they have emissions left. EL509s and other tubes 
> work well, too... A friend in SoCal is reworking them to .ru tubes now.
> 
> Orr's radio handbook has tuned input values in it for a Q of 3 or 4, I 
> forget.
> 
> FYI, the amp I redid above has ORIGINAL PAL marked tubes in it, they do 
> 100% plus. I'm redoing a Johnson CB next, plate modulated and moving it 
> to 10. If it works, I'm going to do 1 for 75M AM :)
> 
> If ya need \ want anything in particular, feel free to ask... I know 
> most of the CB.... I mean Sweep Tube amps pretty well... Made a living 
> converting them to newer tubes a few years ago
> 
> --Toll_Free
> 
> sent from my cell phone
> 
> ------------------------------------------------------------------------
> From: David C. Hallam <dhallam at rapidsys.com>
> Sent: Thursday, November 26, 2009 05:55 AM
> To: AMPS List <amps at contesting.com>; ham_amplifiers at yahoogroups.com
> Subject: [ham_amplifiers] Sweep Tube Amp
> 
>  
> 
> I recently acquired a sweep tube amp and I got it for nostalgic reasons.
> This is my first experience with one of these beasts. It is the
> Side Band Engineers matching amp for an SBE-33 which was first phone rig
> I bought after I got my general class in 1964.
> 
> Anyway, I had to do some work on it before trying to put it on the air.
> It uses 6 - 6JE6's. I see that 6LQ6's are often shown as
> interchangeable. The amp came with 5 - 6JE6 and 1 - 6LQ6. Are they
> really mixable?
> 
> The output is very low. With a single tone drive, it loads to 1.2 amp
> which is spec and seems to be peak output point too. However, the
> output is only about 150W. Is the tube mixture a problem or are all the
> tubes just soft or both? I shudder when I see the price of 6 - 6JE6's.
> Of course, the manual says to use matched sets which is probably
> impossible these days.
> 
> David
> KW4DH
> --
> 
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-- 

"A democracy cannot exist as a permanent form of government. It can
exist only until the voters discover they can vote themselves largess
out of the public treasury. From that moment on, the majority always
votes for the candidate promising the most benefits from the public
treasury, with the result that democracy always collapses over a loose
fiscal policy, always to be followed by a dictatorship."