[TenTec] Omni 6+ - no output on 12M/10M and omni 6+/ power issue

[Phil Chambley Sr.]

Look at the diodes associated with connector 14 on the BPF/Front end 
Schematic.  There should only be voltage on one band at a time, measured on 
connector 14.

Phil C. S4r.
k4dpk
----- Original Message ----- 
From: "Wayne Dial" <w8aju_wdial at att.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Saturday, November 27, 2010 4:37 PM
Subject: Re: [TenTec] Omni 6+ - no output on 12M/10M and omni 6+/ power 
issue


> Thanks Phil, I was not aware of leaky diodes, I did check them with a 
> meter and
> maybe I should just replace them?  I would never have thought the diodes 
> in the
> receiver front end could be the problem!
>
>
> Thanks again,
>
> Wayne
>
>
>
>
> ________________________________
> From: Phil Chambley Sr. <k4dpk at comcast.net>
> To: ken.d.brown at hawaiiantel.net; Discussion of Ten-Tec Equipment
> <tentec at contesting.com>
> Sent: Sat, November 27, 2010 4:02:44 PM
> Subject: Re: [TenTec] Omni 6+ - no output on 12M/10M and omni 6+/ power 
> issue
>
> It is important to determine whether the rig is transmitting on the 
> correct
> frequency when the power is low.  That is why I asked for the SWR reading 
> on
> the 20m antenna.
>
> A common problem with these rigs is leaky switching diodes, and this would
> be a clue to which ones.
>
> As unlikely as it seems, diodes on the receive front end board are a 
> primary
> suspect for this problem.
>
> Phil C. Sr.
> k4dpk
>
> ----- Original Message ----- 
> From: "Ken Brown" <ken.d.brown at hawaiiantel.net>
> To: <geraldj at weather.net>; "Discussion of Ten-Tec Equipment"
> <tentec at contesting.com>
> Sent: Saturday, November 27, 2010 3:20 PM
> Subject: Re: [TenTec] Omni 6+ - no output on 12M/10M and omni 6+/ power
> issue
>
>
>>
>>> Low or no output on a band or bands can be dirty switch contacts. 10,
>>> 12, and 15 haven't had much use in the past few year. It might be a
>>> quarter drop of deoxit on each contact with some vigorous switch
>>> operation might clean them up, or the problem could be a poor solder
>>> joint that went open or nearly open.
>>>
>> The Omni VI uses diode switching for all of that. I don't think there is
>> a single mechanical switch contact (besides the band select push button)
>> involved with the band selection. If it indicates that it has switched
>> to the band you want, then that pushbutton is working fine. The parallel
>> band select lines that go to various boards may need cleaning and the
>> bad solder joint is a possibility.
>>>
>>> Its not possible to be more specific because there can be so many ways
>>> to loose a band or bands (and the crystal is not above suspicion nor the
>>> crystal socket when crystals are used to heterodyne the VFO) unless one
>>> has repaired many Omni VI with the same problem. I doubt there's any RF
>>> difference between VI and VI+.
>>>
>> Omni VI does not use crystal sockets. A bad crystal, or misaligned
>> inductor in the crystal oscillator circuit could be the cause. Don't
>> mess with those inductors unless you have the right equipment to get
>> yourself out of the trouble you may cause. The locations of the coils
>> used for each band is not immediately obvious, and there is a good
>> chance you'll end up adjusting one that did not need adjusting. Make
>> sure you use the perfectly shaped soft plastic twiddle stick for the
>> inductor slug or you will likely break the slug. You will need an
>> oscilloscope with a high impedance probe (like a 10 X probe that only
>> loads the circuit with 10 Meg ohms + small capacitance) to monitor the
>> PLL loop in order to properly set those slugs. And when you have that
>> equipment, the description of the waveform you are looking for is more
>> than I'm prepared to put in this message.
>>
>> DE N6KB
>> _______________________________________________
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>> TenTec at contesting.com
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>>
>
>
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