Dee C. Almquist
w4pnt at HIGHSPEEDLINK.NET
Thu Aug 31 22:26:41 EDT 2006
Evening Ed & Group
I find if its a Valiant, better figure replacing the tank primary, 150pf & the 330pf strings w/ door knobs rated @ 3kv+ & 3rf amps ea. These are costly, about $20. ea. They measure 3/4" x 1" & fit nicely. The secondary "load" caps, that is the triad unit is tough but sometimes it gets burned. Check it out. I use 3kv mica postage stamps there w/ good results.
The Ranger tank is not so fussy, usually those micas are fine, but check them anyway. Your only running 50watts max w/ Ranger. I ALWAYS replace the 18k in VFO box mounted outboard. A prolific use of FB73 ferrite beads 3/4"L x 1/4" dia on every lead going into the VFO box helps (sometimes completely) stabilizes the VFO. The leads you dont want to bead is the yellow output lead going to the buffer & cathode & fil leads. The latter 2 already have chokes. But I would deffinitly replace the .005 bypasses. Oh, The B+ (red lead) feeding VFO I break & add a standoff, use a bead before & after the standoff & BYPASS the standoff to gnd w/ at least .005ufd. Usually the 80m (1000pf pr) micas are ok. If it dont drift dont fix it. The drift problem usually 40m up (the 2 500pf micas) & often I replace these w/ silver micas. Also increase the 470 ohm plate R to the 6AU6 w/ a new 2W. I would definitly change out all bypases in the VFO box. Next check the top ceramics to 40m coil. If drift still occurs, this will have to be replaced w/ an NPO ceramic. Hopefully, after all this, drift will be to a minimum & you can calibrate the dial after re-installing panel.
Hopefully, this info will help all you Johnson restorers. Bottom line, be therough!!
----- Original Message -----
From: "Ed - K9EW" <k9ew57 at gmail.com>
To: "Dee C. Almquist" <w4pnt at highspeedlink.net>
Sent: Thursday, August 31, 2006 9:59 AM
Subject: Re: [Johnson] REBUILDING JOHNSON & other gear
> Thanks for the tip, Dee. I wasn't aware that the ceramics were
> unreliable. Let's see... the electrolytics, the paper and wax, and
> now the ceramics. That just leaves the micas - or are they on the
> list too?
> I have a Ranger with the dreaded VFO instability. I replaced the 18k
> 2w resistor (it was down to 13k), the 6AU6, and the 12AU7A, but that
> wasn't enough. The OB2 was holding within 1v key-up to key-down so
> that seems OK. So it looks like I'll have to go deeper into the VFO
> box. I've seen conflicting postings about putting the 18k resistor
> outside the VFO box; what's your opinion on that?
> Tnx es 73,
> ed - k9ew
> On 8/31/06, Dee C. Almquist <w4pnt at highspeedlink.net> wrote:
> > Dear AM'rs
> > I rarely make suggestions but.... ANYONE overhauling BA's should keep in mind, these rigs are many years old. And even though the capacitors look ok is being mislead & lots of frustration. My shop policy is (especially Johnson) CHANGE OUT ALL CERAMIC BYPASS CAPS & check every resistor for value. This shotgun method has saved me time & added to customer satisfaction on every Ranger & Valiant (same w/ other gear) that I restore. It pains me to read of a fellow Anchorite ready to dump his set due to repeated failure because of assuming "the rest" of one time quality parts are ok, then comes another failure, etc. There is nothing better to do in restoration but to assume NO cap or resistor is good after all the yrs since it was new. Its time consuming but worth the effort.... & un-needed frustration.
> > Warm 73 to all
> > Dee
> > Johnson mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/johnson
> > Help: http://mailman.qth.net/mmfaq.html
> > Post: mailto:Johnson at mailman.qth.net
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