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

[wf2u at starband.net]

A long time ago I read somewhere - it may have been even in the version of
the 51J-4 manual I have; I'll have to dig it out and look at it - that the
pot is set for the compromise between maximum gain and minimum noise...
In my 51J-4 when I aligned it last about 8 years ago, I set it near the
minimum resistance, just before the noise became perceptively more
intense.

BTW I'm looking for the metal lever for the filter switch, as mine has a
non-original concentric knob for the filter switch/phasing.

73, Meir WF2U
Landrum, SC

> 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 --
>
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