Thanks for the suggestions. A few days of sleuthing and talking to Garry at
Ten Tec led me to discover that all the input (D1-D8) switching diodes on
the Hi-Pass filter board (81330) were "open". Garry said In4148's could be
substituted, which I did, and now all the sections seem to test OK and
switch appropriately...but the same symptoms remain: all functions seem
normal, but sensitivity is off by around 4 S-units. None of the RF chokes
seem to be open, and bypassing the Lo-pass FX board by selecting the
external receive antenna makes no difference. I am looking at the 1st Mixer
now, although I do get the appropriate 20dB reduction when switching in the
attenuator, which shuts off the RF stage, so I am still befuddled.
One anomally I see is the the voltages on the band switching diodes seems a
bit low. I would have expected a lower voltage at D1 as it has more
resistance in the path, but the reverse is true and it reads about 9.4v as
opposed to the other 7 Hi-pass sections at about 7.25v when selected. That
still seems plenty to bias the diodes and pull in the low-pass relays, but
curious.
=Vic=
WA4THR
____________________________________________________________
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Paragon problem
From: Wade Staggs <tvman1954@gmail.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Wed, 9 Jul 2014 17:39:05 -0500
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
*Far from being an Expert myself, The first place I would look would be the
RX High Pass Filter Board ( 81330 ) At the Antenna Input to the High Pass
Filter Board, there are two LC Coils and a Diode ... Any of which could be
Shorted or open in the case of the LC Coils. You should be able to inject
signal or an antenna input on each side of the High pass Filter Board. I
would use a Clip Lead and touch my Antenna to the output connection from
the board and see what happens. The High Pass Filter board uses Switching
Diodes to select the correct Filter for each Band. I am believing that like
Ivory Soap, 99 44/100s percent sure that the problem is somewhere on the
High Pass Filter Board.*
* 73 and May God Bless from Wade/KJ4WS*
On Wed, Jul 9, 2014 at 5:20 PM, K8JHR <jrichards@k8jhr.com> wrote:
> Hi Vic -- I am far from expert on this, but I wonder if you can locate
> ANOTHER protective diode in the receiver circuit. I once killed my Omni
> VII receiver by hot-switching an "active" receive only antenna - the power
> connector arced to case ground of a bias-tee injector as I plugged it in,
> and that fritzed the receiver. Gary at TenTec service called me to
explain
> it before he fixed it, and I believe he said there were multiple diodes to
> protect the rig in such cases.
>
> So... perhaps you have more than one diode or fuse or other prophylactic
> device to check?
>
> -----------------------------K8JHr ------------------
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