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

[Wayne Dial]

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
> _______________________________________________
> TenTec mailing list
> TenTec at contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
> 


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