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@hawaiiantel.net>
To: <geraldj@weather.net>; "Discussion of Ten-Tec Equipment"
<tentec@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@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|