[R-390] Pulling crystal frequency in R390A

[Bill Hawkins]

Roger,

You are a most respected resource for this list.

The younger generation wants close agreement to the specs, using gear
that wasn't dreamed of in 1960.

Thank you for bringing the proper perspective to the process of
measurement and alignment.

Bill Hawkins
 

-----Original Message-----
From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Roger
Ruszkowski
Sent: Thursday, December 03, 2015 11:17 PM
To: ngietz at mymts.net; r-390 at mailman.qth.net
Subject: Re: [R-390] Pulling crystal frequency in R390A


Nelson,

You could have a problem in T205 if you can not get a good band pass in
the 1KHz bandwidth position.
The band does not "peak" you just try to put the center between the
filter skirts.
Output in the 1 KHz band will be lower than in the 2 KHz band pass. 
The band width of the 1 KHz filter does not change with adjustment.
The circuit was designed and built close enough to specifications.
The adjustment just lets you move the band pass to center on the crystal
where ever that may be.
At 2 KHz band width the filters are close enough to be over the 455 KHz
crystal filter center.

6.2.17 in the Y2K manual give an alignment procedure for L503.

C524 in Z501 could be out of range.
A change of a few PF could let you bring the circuit back in alignment
using L503 as it is.

Respectfully,

Roger Ruszkowski

 
-----Original Message-----
From: Nelson Gietz <ngietz at mymts.net>
To: r-390 <r-390 at mailman.qth.net>
Sent: Mon, Nov 30, 2015 9:40 pm
Subject: [R-390] Pulling crystal frequency in R390A

Going thru the alignment process on this R390A on the bench, I find that
crystal Y501 for the narrowest bandwidths is about 80 Hz above the
required 455 kHz. In the neutralizing procedure C520 adjusts well, but I
can't get L503 to tune low enough to resonate the 1 kHz bandwidth at the
same frequency. There is no visible evidence of damage or tinkering in
T205. 
Could the two problems be related? (The crystal resonant frequency is
about 455.076 kHz out of circuit.) Also, has anyone heard of or tried
"pulling" that crystal frequency to compensate? How would that work in
this circuit?
Nelson


 
______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:R-390 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:R-390 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html