[R-390] Calibration Osc and 2nd Osc questions

[thoyer]

Got it, thanks.

Keeping this thread updated as to my progress (or lack therof....)

Didn't get as much time as expected to work on it yesterday. I was able to
procure another 14mc xtal which I thought would fix the no output issue from
the 2nd xtal osc - nope, didn't work. 

I pulled the RF deck and found that if I flip it upside down and support it
on a couple wood strips above the main chassis that the two harnesses will
reach and allow me to probe around on the underside easily. 
 
Measuring all of the positions on S401 and S402 I had the following results:

All of the positions on S401 read -0.16V - All of the manuals show this
should be -10v or so. I tried a couple different 5654's in V401 with no
difference. The 5654's I have all test good on my Hickok.

All of the positions on S402 read approx 175v with the exception of the dead
11mc position which measures about 140v - suspect that the mica across the
variable for that circuit is leaky. 

The resistances and voltages around V401 all seem reasonable except for the
voltage at pin 1 (E402).

I should have more time today to spend on it.

Tom

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of Larry H
Sent: Saturday, December 02, 2017 8:38 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] Calibration Osc and 2nd Osc questions

Tom,  The maint man says to connect your 50 ohm sig gen output to the R-390A
using the impedance adapter DA-121.  The reason I bring this up is that the
adapter has a 55% signal loss, so when the book says the sig gen output
reading should be less than 4 uv, the actual signal level at the rx is about
1.8 uv.  Although 1.8 uv sensitivity is ok, as Bill points out, good levels
of sensitivity can be achieved.  The ones I've worked on usually end up at
.6 uv above and below 8 mh.
If the 1st var IF aligns ok, then the problem could be in the 17 mh osc or
1st mixer.
Regards, Larry

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