[Heathkit] SB-610 phase networks needed

[Sandy]

I FINALLY found my formulas late last night!  There is VERY little desigfn 
information on the phase shift oscillator.

Minimum network is three sections, "usual" is 4 or even 5 sections.  What I 
worked out was this:

Resistors are 220K ohms.
Capacitors are 150 pf. for 1950 Hz., 200 pf for 1500 Hz and near 300 pf for 
1000 Hz.  The gain of the oscillator stage is certainly over the required 
"minimum" of 29.  If you want to adjust the frequency precisely, shunt the 
capacitors with smaller values as desired, as long as they all stay the same 
increment. one of the "end" resistors can be variable over a small range as 
well (say a 180K resistor and a 50 K trim pot.)

The frequencies are not critical 1000-1500 for "low tone" and 1500-2000 for 
"high tone".  Usually about 400-500 Hz. difference between the tone 
frequencies chosen.  I would not use anything above 2-2.5 khz high tone and 
nothing below around 750 Hz low tone.  Most SSB audio circuits roll off the 
"bassy" lows and rolloff highs at around 2.7 Khz.  (Unless you run into one 
of those "Broadcast quality" morons who like to occupy the whole band with 
their "hi-fidelity"!)

Hope this helps
73,

Sandy W5TVW

(Hope my figures are right!)


----- Original Message ----- 
From: "K3PID" <k3pid at sbcglobal.net>
To: "heathkit" <heathkit at mailman.qth.net>
Sent: Friday, September 21, 2007 3:08 PM
Subject: [Heathkit] SB-610 phase networks needed


I am restoring an SB-610 monitor scope and find that the two tone generator 
which is supposed to have frequencies of 1500 Hz and 1950 Hz have both 
shifted. I am reading about 1900 and 2350. The phase shift networks P.E.C 
84-39 & 84-40 are the frequency determining components and my guess is that 
the internal capacitors have shifted enough to move the frequency. I realize 
that the exact frequency doesn't much matter as long as it is inside the 
passband but I would like to make it match the specification...

Does anyone have these in NOS or if not then does anyone have the detailed 
specifications for the networks?


Regards
Ron H. - K3PID

_______________________________________________
List Administrator: Duane Fischer, W8DBF
** For Assistance: dfischer at usol.com **
$$ See the vintage area on the HCI web site - http://www.w9wze.org $$
Heathkit mailing list
Heathkit at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/heathkit


-- 
No virus found in this incoming message.
Checked by AVG Free Edition.
Version: 7.5.488 / Virus Database: 269.13.28/1021 - Release Date: 9/21/2007 
2:02 PM