[R-390] alignment assistance for an R-390A beginner

Tue, 4 Mar 2003 06:04:05 -0500

Antero,

It sounds like your PTO is not outputing 2445 KC when your KC knob is at
7+000 with the cams aligned at the marks.  Here's what I would do:
1.  Set the zero adjust mechanism in the center of it's range by tightening
down the ZERO ADJ knob, spinning the KC knob one way and then the other
until it stops, setting the KC knob near the center of that range between
the stops, and then loosening the ZERO ADJ knob.  The zero adjust mechanism
is now near the center of its range.
2.  Set the camshafts at their alignment marks.  Don't worry about whether
the dial reads 7+000 or some other value.
3.  Loosen the clamp that connects from the KC shaft to the oldham coupler,
which ties the KC shaft to the PTO.  This will decouple the KC shaft from
the PTO.
4.  Rotate the PTO shaft by spinning the oldham coupler until the PTO is
outputing 2445 KC.  If you don't have a frequency counter, you can just use
the CAL function to find the carrier (at 8.0 MC).  You now have the
camshafts aligned with the zero adjust near the center of its range and the
PTO putting out 2445 KC.
5.  Retighten the clamp connecting the KC shaft to the oldham coupler.
6.  Look at the frequency readout.  If it is very far from 7+000, you will
have to remove the front panel and adjust the veeder root (frequency
readout) by loosening the gear clamp and rotating the gear on the right side
of the veeder root mechanism.  If it's close to the correct reading, you
should be able to adjust it with the ZERO ADJ method.

This will get the camshafts aligned at their marks when the PTO is at 2445
KC with the zero adjust range near center and the dial readout at 7+000.
That's your starting point.  If the radio was aligned when the camshafts
were in their misaligned positions, the radio will now be in need of a good
alignment.

Walter Wilson - KK4DF
http://r-390a.us
(REAL Radios: R-390A, R-390, T-368E, Ranger, Thunderbolt, KWM-2A)

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Tuesday, March 04, 2003 3:03 AM
Subject: [R-390] alignment assistance for an R-390A beginner

Dear group,

this is the first, but probably not the last time I write to you.

I have just recently acquired an R-390A receiver from Fair Radio. Having my
background in humanities (linguistics), I chose the "checked" option in hope
of a working unit. After having paid almost another USD 550 for shipping,
value added tax and customs duties, I finally have my radio on my desk here
in my hometown of Nurmijarvi, Finland. I think I got a nice receiver: it has
an engraved front panel (without a manufacturer's tag), one fuse, the PTO is
a Collins, power transformer from EAC, AF subchassis from Capehart... well,
all in all, a nice example of the modular construction principle! These all
are from the 1960-1961, or thereabouts, contracts.

I resisted the temptation to apply power to it before I had changed the
critical capacitors in the IF subchassis (C-531, 547, 549, 553). Obviously,
I also had to make the necessary changes in the power supply for our 230
VAC. Further, I have now changed all the capacitors in the AF subchassis
listed on KK4DF's homepage.

At this point, the receiver is working surprisingly well, taken into account
the little work I have done so far. Signals are present on all bands, random
checks into tube sockets show approximately the correct resistance and
voltage values, and test point E607 provides exactly 150 VDC.  In fact, my
R-390A receives just about every signal my other receiver, a Drake R8B,
receives. Not bad, although I do notice that the Drake is more sensitive on
the medium wave band, at least so far... Of course, my R-390A probably has
who knows how old tubes and it probably is not perfectly aligned, which
brings me to, yes, alignment issues:

I can at the moment adjust the frequency display to indicate the correct
frequency as described in the Operator's manual, but I notice that, using
the "zero adj", I end up at the very limit of the KC knob's range of
movement without the last three digits of the display changing. More
specifically, I can't move the KC knob to the right (higher frequencies).

Further, the mechanical alignment at the frequency reading of 07+000 is
slightly off, with the cam plates (all of them) better in place at frequency
reading 07 990. Now, in such a case, the manual suggests the remedy is to
set the cam plates to their correct position, and then manually change the
frequency reading to 07+000. In my case, then, I would have to add 10 kHz to
the reading. But here's where my confusion already starts: if I add 10 kHz
to the frequency reading, I can't correct that using the "zero adj." as I'm
already at the limit of its range. Further, the nice balance of
approximately 35 kHz above and below a "XX 000" reading on the frequency
indicator will be gone, right?

So, as you notice, I'm a bit confused as to what setting affects what other
settings and what the correct order of doing things is. Is there a procedure
described somewhere that corrects the frequency error, centers the "zero
adj." to the middle of its 15 kHz range, and restores the 35 kHz on both
sides of a "XX 000" reading? Of course, what I'm after is a non-techical
description using layman's terminology and definitely not using signal
generators, oscilloscopes and other equipment that I don't happen to own! I
have downloaded TM 11-5820-358-10 and -35, and the 21st century technical
reference, but can't seem to be able to extract the information I'm after.

Any help you can provide is received with gratitude!

Greetings from Finland,

Antero Nordlund

[email protected]

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