[TenTec] ParagonII Audio BP Fade Feature Mods

[Steve N4LQ]

Interesting. My schematic showed R64 to be 33k but information from the chip 
manufacture suggested a 10k should be used, which is in fact used in the 
second stage. I used my substitution box with leads clipped across R64 and 
cranked down the resistance for best performance. That let me to 10K.
I no longer have the Paragon 2 so I can't refer to the part numbers but 
there is a resistor, 33k, at the input of the first filter chip which drops 
the audio level considerably. This can be lowered even further if you want 
more gain from the filter. I actually prefer the gain to peak up a few DB 
when peaking the filter.
Glad the mod worked Scott. 73
Steve N4LQ
----- Original Message ----- 
From: "Scott Prather" <sdprat at worldnet.att.net>
To: <tentec at contesting.com>
Sent: Monday, December 20, 2004 8:00 PM
Subject: RE: [TenTec] ParagonII Audio BP Fade Feature Mods


>I would like to thank Steve for posting this information concerning
> incorrect component values in the Paragon II audio filter circuit. 
> Minutes
> after I received this e-mail last night, I checked the IF/audio board in 
> my
> Paragon II, and while I found that R65 was the correct value, R64 was not.
> The Paragon II schematic shows that R64 is supposed to be 10K (as Steve
> mentions), but my audio board had a 33K.  The difference in audio filter
> performance when R64 is changed from 33K to 10K is striking, and the 
> filter
> is now a true asset to the CW performance of the radio.
>
> My biggest complaint regarding the documentation for the Paragon II is 
> that
> unlike the Paragon I, the manual does not include a component-layout 
> drawing
> (at least this is the case with the Oct, 1993 manual I have).  So to do
> something as simple as checking these resistor values, you have to remove
> the board, guess which IC is which, start counting IC pins and match the
> schematic to the board.  Checking all the resistor values in the audio
> filter section took some time as it was necessary to flip the board over
> many times to see what traces go where, and what part is tied to each 
> trace.
>
> Scott
> N7NB
>
> -----Original Message-----
> From: tentec-bounces at contesting.com
> [mailto:tentec-bounces at contesting.com]On Behalf Of Steve N4LQ
> Sent: Sunday, 19 December, 2004 16:41
> To: tentec at contesting.com
> Subject: [TenTec] ParagonII Audio BP Fade Feature Mods
>
>
> If you have a Paragon II and feel that the Fade - BP audio is broad and
> ineffective, check the following value on the IF/AF board. This board is
> located on the bottom/front RH side. You must remove the bottom shield of
> course.
> R65 should be a 33k according to the schematic. Mine was a 3.3K. This
> incorrect value prevented the first stage of the filter from resonating 
> near
> the desired frequency while the second stage worked fine, since it had the
> correct value, 33k.
>
> Have you noticed how the audio gain seems to decrease when turning up the
> fade control, even at resonance? Change R64 from 33k to 10k. This will
> equalize the gain when the filter is engaged.
>
> Once the filter is working properly, it becomes a wonderful too for
> improving CW copy.
>
> 73
> Steve N4LQ
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