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Re: [TenTec] Omni VII Internal Tuner failure - advice please.

To: tentec@contesting.com
Subject: Re: [TenTec] Omni VII Internal Tuner failure - advice please.
From: "Dr. Gerald N. Johnson" <geraldj@weather.net>
Reply-to: geraldj@weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 03 Jan 2011 18:58:22 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>

On 1/3/2011 5:45 PM, Stuart Rohre wrote:
> Don't fear returning your radio to Ten Tec if you have the orginal box
> and padding, or can repack appropriately.  Insure the shipment as well.
> However, before going to that trouble, get the internal tuner exposed by
> taking off the cabinet, and if you have a DVM with diode check, check
> the diodes on the tuner board with the meter, (Radio off of course).  If
> you don't get 0.6 volt across one direction of each diode, you have
> found a bad one.  The other direction should not show a voltage barrier
> of 0.6, unless for some reason two diodes are in shunt.

Also check for a dirty connector by sliding the connectors off and back 
on a few times. Then check for loose board grounds by tightening the 
board mounting screws.

Schottky diodes are better for detectors and may have less than 0.6 
volts forward drop.
> The main use of diodes in the tuner will be for SWR bridge, and for
> relay back EMF suppression.  You can use the ohms scales to check the
> relays for correct contact action.  This might require an "Elmer" if you
> are not accustomed to working on your own electronics circuits.
> The diodes are the most prone to fail component in any SWR measuring
> circuit.
> Of all your options, checking the diodes is the easiest to do yourself
> and least costly.  IF diodes test bad, you can get the parts from
> distributors or Ten Tec, and carefully solder them in to replace the
> originals.  Just pay attention to polarity, Make a sketch of which
> direction any bands are oriented on the diodes, before removing old ones.
> -Stuart Rohre
73, Jerry, K0CQ
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