[R-390] 51J-4 IF gain set

[Roy Morgan]

At 10:44 AM 11/20/2007, you wrote:
>Does anyone know of a reference in the Collins 51J-4 instruction book to 
>setting R-187 IF gain-set?

Charles,

I found the article in HSN about this:

"Another potential cause of insensitivity on all bands is R187, a 10K ohm 
screwdriver adjustable pot with lock nut beside the BFO pitch shaft, which 
determines the gain of the 3rd IF amplifier. My manuals have no 
instructions for setting R187. I have assumed the correct setting is 
determined by the J4 (500 KC)
IF performance test per paragraph 5.3.7. In my experience, the 500 KC IF 
performance criterion is met with R187 set near minimum resistance (nearly 
maximum gain of the 3rd IF amplifier). For J3's and R-388's this setting 
may be considerably different because the J4 has mechanical filters which 
in turn have
considerable insertion loss. If anyone has any information or opinions on 
this, please write me so that we can share the information with other 
Hollow Staters. "

I found this in the HSN document called
"Selected Reprints from The Hollow State Newsletter - Issues 1 through 30
Collins 51J's, Hammarlund & Other Receivers  2000"
the first reprint is: [Lankford, Issue #20, pgs 3-6]

which begins the compilation of articles:  HSN-Hammarlund.PDF  Issue 20 can 
be found on the HSN wibsite  http://www.hollowstatenews.com/  under 
Archives - Older Issues.  The direct link to that issue is:
<http://site298.mysite4now.com/barryhauser/archives2/HSN-Issue20.pdf>

The  compilation is on the HSN website under "Best of Hollow State", 
"<http://site298.webhost4life.com/barryhauser/archives/HSN-Hammarlund.pdf>Hammarlund 
Also includes Collins 51-J & other receivers "


I see R-187 shown in a photo in the 51J-4 manual 4th Edition, 09-58.  This 
is titled "Communications Receiver 51J-4 ... Collins Radio Company" and has 
the dates 1957 - 1958 on the title page.

Paragraph 5.3.7 in that manual can be summarized as:

... AVC-off. 500 Kc signal to  pin 7 of V106. VTVM on Diode Load resistor 
to chassis. Input to pin 7 of V106 should be between 25 to 40 uV for 4-volt 
reading at diode load.


Roy


- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing
13033 Downey Mill Road, Lovettsville, VA 20180
Phone 540-822-5911   Cell 301-928-7794
Work: Voice: 301-975-3254,  Fax: 301-975-6097
roy.morgan at nist.gov --