[R-390] Second LO and bad xtals

[Craig Heaton]

Hello Alan & All, 

Been watching this thread and the AM Forum with interest. 

Here goes: Test point E402 and the grid leak voltages in the Y2K manual
suggest a value between -4 to -11 VDC. Guessing here that those measurements
were made with a USM-116 (HP-410 B or C) with an input Z of 100 megaohm or
so. 

Considering most of our newer test equipment is lucky to have an input Z of
10 megaohms; would it be better simple to use a frequency counter to check
for correct frequencies per setting of MC knob??????? Perhaps using a pocket
size freq counter with a telescoping antenna held next to V401 would be a
better indication? Lacking a correct frequency, then check for voltage at
the pins of V401 or consider which crystal might be toast??

Craig, 

-----Original Message-----
From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Alan Victor
Sent: Friday, September 26, 2014 2:29 PM
To: r-390 at mailman.qth.net
Subject: [R-390] Second LO and bad xtals

In an earlier post I noted a bad 9 MHz crystal, off frequency by as much as
15 kHz at injection. Indeed, I found 4 other bad crystals for the 10, 6, 17
and 23 MHz band. In all cases 13-15 KHz error. The net of this, if you see
issues in obtaining PTO end points as well sensitivity, check those crystals
in the second LO sub chassis. Either the heater or some significant
vibration over the years took a number of these units out.
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