[Johnson] Need Info on Johnson Viking Ranger 12V PTT Circuit and other improvements
Michael Hardie
mike46 at shaw.ca
Thu Jun 4 11:46:37 EDT 2009
Joe,
I don't have the exact information you requested but homebrewed a 12 volt
PTT relay installation using the dial light voltage through a voltage
doubler/resistor circuit for power. If you're using the older Amphenol
style 2 pin mic jack you'll need the type of doubler circuit that has one
side of the output grounded. The actual PTT connections to the mode switch
were as per the Ranger Operator's Manual but with a 4PDT relay (One set of
contacts not used.) it was possible to have the red transmit light only
illuminate with the PTT pressed. (When in the AM mode, CW mode same as
before.) If there's interest I could make photos of the schematic and
installation and email them, uploading something to the archives is way
beyond my capability.
The 12 volt PTT relay mod has a couple of real advantages, you can rotate
the mode switch all the way to standby without transmitting and there's no
"high" voltage on the mic.
About 6 months ago I acquired my Ranger. It had a dead short inside the HV
choke that turned out to be caused by the insulation cracking off one of the
leads and the bare wire contacting the choke's end bell. Brittle insulation
on the choke and transformer leads due to aging is a common Ranger problem,
so if you don't intend to do major renovations be very careful around these
leads. Apparently it's a common fix to install heat shrink tubing on all
the leads, I ended up removing the HV choke and the power transformer and
replacing each lead with new wire. For me this was a big job.
The HV and LV electrolytics in this Ranger were OK. The "+" lead on each
was unsoldered and they were individually connected to a reforming jig, but
actual reforming wasn't necessary because the leakage was a fraction of a
milliamp. Various caps in the modulator section had been changed to values
that were about 10 times original, these were all removed and replaced with
caps that were as close to original values that modern components would
allow. Also this led to downloading a Ranger construction manual and
checking all the wiring which turned up many incorrect connections. The
feedback winding on the mod transformer had been intentionally shorted to
ground, after unsoldering and removing the short the reason became apparent,
huge continuous oscillation as soon as the AM mode was selected. The
problem turned out to be that the connections to the two 1614 plates were
reversed. (Suspected this from DX-100 days) The two electrolytic caps under
the small subchassis were leaky and were replaced with one 30 uF cap.
Several of the disc caps and the 11K resistor near the clamp tube had been
replaced with a variety of oddball valued components, so they were removed
and proper value components installed. I haven't yet changed the power cord
to a modern 3 wire one with a fuse in the chassis, but this is a very good
idea from an operator safety stand point.
Probably more information than you wanted, good luck with your Ranger.
Mike VE7MMH
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