[R-390] IF Subchassis

[Cecil Acuff]

Simple test....lift one end of the crystal and see what one looses....

Should solve that!

Cecil
K5DL
----- Original Message ----- 
From: "KA9EGW" <ka9egw at britewerkz.com>
To: <r-390 at mailman.qth.net>
Sent: Sunday, February 27, 2011 1:49 PM
Subject: Re: [R-390] IF Subchassis


> Figure 106 is the chassis main harness breakouts.
>
> TM11-856, Fig. 107, upper left corner--S501 shorts out the crystal in
> position 3/4/5/6 [e.g. 2/4/8/16kc BW] although the way the schematic is
> drawn it's not as apparent as it could be.  It's much clearer drawn on 
> p.3-9
> of Y2KR3.
>
> Getting two different bandwidths [.1 and 1] out of the same single-crystal
> filter is accomplished by q-spoiling resistors R502 or 503 as detailed in
> Y2KR3 Section 3.2.9.2:
> "When the BANDWIDTH switch is turned to .1, the crystal circuit is loaded 
> by
> C503 in series with the combination of R502 in parallel with the series
> combination of C501 and R503. The exact value of R503 is chosen between 
> 560
> and 2,700 ohms, to provide a bandwidth of 0.1 kHz.
> When the BANDWIDTH switch is turned to 1, C501 and R503 are removed from 
> the
> circuit, and the bandpass is increased to 1 kHz. The value of resistor 
> R502
> is selected between 33K and 68K to provide a bandwidth of 1 kHz. When the
> BANDWIDTH switch is turned to 2, 4, 8, or 16, T208 is coupled directly to
> the control grid of V501 through capacitor C501, thereby removing the
> crystal from the circuit."
>
> Now go take your Aricept.  I'm done with this.
>
> 73, Brian KA9EGW
>
>
>
> -----Original Message-----
> From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
> On Behalf Of rbethman
> Sent: Sunday, February 27, 2011 12:52 PM
> To: R-390-List
> Subject: [R-390] IF Subchassis
>
> In spite of all assertions that Y-501 is SOLELY used as a crystal filter,
> It would perhaps be of value to *carefully* look at TM 11-856, Figure 106.
>
> Looking at the schematic, It is very obvious that Y-501 is ALWAYS tied to
> the control grid of V501 without regard to the position of the S-501 wafer
> of the bandwidth switch.
>
> The other end of Y501 is tied from its other side to ALL the positions of
> the S501 wafer for all filter positions from 2, 4, 8, and 16 positions.
>
> I can indeed read the cited paragraphs!  I've done so.  They do NOT, 
> however
> "change" the circuitry and the feeding of the internals of Z501 to V501
> whatsoever.
>
> Exactly "how" two positions of S501 result in .1Kc and 1KC filtering, I do
> not know.  I won't dispute the "written" function in the cited paragraphs.
>
> However, it CANNOT be dismissed NOR ignored that Y501 is in "play" and 
> feeds
> V501 ALL the time.
>
> Bob - N0DGN
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