[R-390] PTO

[David C. Hallam]

Roy,

I guess I should review my notes before opening my mouth.  It is not a plug
and play interchange but is readily doable.  The R-390 get screen voltage
from a dropping resistor in the B+ line while the R-390A has a separate 150
VDC regulated supply.  Since you will have to rewire the power cable anyway
(the R-390A cable is too short), the changes are minor.

The R-390A mounting bracket will take some changes to mount in the R-390.

Bottom line for me is that I would not hesitate to make what I believe minor
changes to use a R-390A VFO to use in a R-390 if I had to.

David
KC2JD

-----Original Message-----
From: Roy Morgan [mailto:roy.morgan at nist.gov]
Sent: Monday, December 05, 2005 5:25 PM
To: Richard Loken; David C. Hallam
Cc: R-390 at mailman.qth.net
Subject: RE: [R-390] PTO


At 05:06 PM 12/5/2005, Richard Loken wrote:
>On Mon, 5 Dec 2005, David C. Hallam wrote:
>
> > According to the information I have, the only differences are the RF
> > connector and the power cable.  I think the power connector itself is
the
> > same.


Do be careful here.

Radio           PTO
R-390/URR:  70H-2
R-390A/URR: 70H-12

  The power plugs may be quite different: one having a different number of
contacts than the other one, even though they are both the small hex shaped
Winchester type.

It's not clear to me but the B+ supply to the PTO may be thought the output
coax in the R-390/URR PTO (70H-2).  The output voltage may be specified as
different, but likely would work ok.

The frequency span, plate voltage, heater voltage and current, filament
voltage and number of turns are the same.

I can't say about the physical size  and mounting point dimensions.

Any one with a 70H-1 PTO: It will *not* work in either of these radios,
send it to me.

Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
7130 Panorama Drive, Derwood MD 20855
Home: 301-330-8828 Cell 301-928-7794
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