[Johnson] Newby Valiant Owner questions

[Dee C. Almquist]

Hi John
I rarely reply on questions but I have restored quite a few Valiants &
Rangers. Glenn's suggestion on grounding is well founded, you dont want to
leave anything to chance. IN ADDITION, it has been my experience on the
Valiant, because of the hi rf current in the tank circuit tank caps must be
rated @ nr 2A (rf) or better or they will heat. The fact that your PA
current is creeping indicates cap heating. As the caps get hot the pa
currnet will go ballistic. Rarely have I had to replace the triad load cap.
They are tough but best to check leakage anyway. Most likely its the tank
resonance caps. When a band wont dip & pa current runs hi or pegs meter, cap
is either open or shorted. Of coarse a bad ground will cause that also. The
plate tank caps I replace are doorknobs 6kv @ 5A @ about $20. ea. I have
tried a bunch of caps including ceramic rated 10kv & higher & they all heat
(not hi enuf current rateing). You can check the heat w/ a infared heat
probe (Radio Shack) or touch caps (tx hi voltage OFF!) & if hot, caps wont
work in there.
Hope this helps. Oh, one more suggestion. Better check the nychrome wire
meter shunt for meter accuracy. I use an HP ma meter in series or clamped
across shunt to determine currect reading. Most times that shunt is far too
long & needs to be shortened.
Dee, W4PNT

----- Original Message -----
From: "John Lawson" <jpl15 at panix.com>
To: <johnson at mailman.qth.net>
Sent: Saturday, September 03, 2005 8:50 PM
Subject: [Johnson] Newby Valiant Owner questions


>
>    Hello List.
>
>    I've owned my share of BA gear since BA was nearly state-of-the-art,
and
> I have a couple of racks full of tube stuff now - I've done a good bit of
> tube design, but mostly audio and ultrasonic gear.
>
>    I have a fairly nice Valiant - it's the first Johnson transmitter I've
> owned since that Viking II I got from an Elmer at age 9.  When I got the
> rig it was reasonably clean and had a set of 866s and five 6146s in it.
> So I replaced the rectifiers with the IR plug-in stacks and bought a nice
> set of 6146Ws for it - quasi-mil tubes, should be twice as good, no?
>
>    Okay - first Valiant lesson: 6146s!! Maybe "A"s....
>
>    Subsequently, I went thru all the caps and found a bunch of them in the
> RF power section were either leaky or badly off spec. So I dug up some
> replacements and shotgunned them all, including that little composite
> multi-section device (C42) - with ceramic disc units of about 6KV.
>
>    After replacing the finals with 6146As - I have the problem that
running
> thru a BIrd into a dummy load -the rig plate current 'runs away' on any
> band lower than 20M.  (I never tried 10) 40 holds for 30 seconds or so, 80
> starts climbing right away, and 160 just won't resonate at all.  It's hard
> to diagnose this because I don't want to french-fry a bunch of good tubes
> while thrashing about.
>
>    I have neutralized it according to the manual, BTW.
>
>   Before digging in to this further, I thought to ask if this behavior
> seems 'familiar' to anyone - as in "Oh, Yeah - paint C127 dayglo orange
> and re-tighten the left rear bolt on the mod transformer - guaranteed
> fix!"  I asked this question on the AM Radio list, and got some good
> (eye-opening) info concerning the various flavors of 6146 tubes - but I
> still need to get 'er stable - so I can get on 80M AM - woo hoo!
>
>    Any thoughts - help - advice - sneers - groans - would be much
> appreciated!
>
>
> Thanks!!
>
> John  KB6SCO
>
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