[TenTec] Omni V I Assistance Needed

[Byron Cordes]

The radio is a Omni VI.  Radio does rx and tx . can here and talk to people even on 20 meters where that vfo noise is . Higher noise floor on 40- 160 you don’t here the vfo noise but on 20 meters it is very loud higher than the people talking when tuning . Stop turning vfo and radio sounds normal with people talking .

Sent from my iPad

> On Sep 29, 2018, at 5:23 PM, MadScientist <dukeshifi at comcast.net> wrote:
> 
> Sorry, I misread… I was focussed on a previous radio (a Paragon).
> 
> Your problem is most certainly due to the fact that the 5.0 to 5.5 MHz PLL is going out of lock. This model does not produce any out-of-lock fault regardless of the lock condition of the PLL so it can be out-of-lock with no indication of that condition. The radio will still produce normal band hiss but you will not be able to tune in signals.
> 
> Oddly, he radio will still transmit in this condition, but well out of the Ham bands! It will transmit on the frequency at which the VCO settles when out-of lock, about 14.6 MHz, regardless of dial setting or display readout reading. It will also be very unstable.
> 
> From what you describe (now that I am on the right page model-wise) i would suggest replacing the dual gate MOSFET in the loop IF. 
> 
> I recently repaired an Omni 6 that had the same problem as your Omni 5 has. That FET was the culprit and what’s worse, it pulled the alignment due to leakage of the device. It was highly intermittent. The heat/cool method was the only way I could point to it, but monitoring the loop test point was the only way I could prove it to myself.
> 
> The way to really determine if this is the fault is to put a voltmeter on the 10K resistor test point of the loop IF (That resistor stands up on the board whereas all of the others lie down, and the test point is the high end of that resistor (thankfully). Then, from a cold start of the radio, monitor that voltage as the warmup progresses. While the PLL will lock with as little as 80 mV at t his point, it will be unstable. You SHOULD get, as I said, >300 mV at all three band test frequencies.
> 
> The actually band selection is not important because this PLL operates the same regardless of band. However, an exception exists in that the PLL will not tune to “500” position on 40 meters.
> 
> Also, the PLL tunes in opposite directions on low bands and high bands. That is why I chose 20 meters to select which coil to peak at what frequency.
> 
> I used a BF988, available from Littediode on eBay to replace the loop IF FET. The devices I get for Littlediode always work so they are a safe seller IMHO.
> 
> You may need to align the loop IF if you do not get at least 300 mV DC on the loop IF test point on all portions of the band (14.000, 14.250 and 14.500) since this is a broadly tuned LC IF stage that was likely originally aligned using a sweep generator.
> 
> I approximated the sweep generator by aligning the three IF coils, one a tach frequency test point. The left most I peaked at 14.200, the middle one at 14.250 and the right most one at 14.500 (radio on 20 meters, of course).
> 
> Gary
> 
>> On Sep 29, 2018, at 3:42 PM, Dry Martini Holding Company😎 <qrp at kg4kgl.net> wrote:
>> 
>> I have a similar issue with my V.9. When I first turn it on, it will be fine then recv audio will drop out. If I leave it on for 15 or 20 min, recv audio becomes normal again and is fine the rest of the day. 
>> st point
>> I sent mine to steve Yudell in Florida and he had it for a couple of weeks and it worked fine for him after he went through it. Now that I have it back it has started doing it again. I just don’t feel like boxing it up and sending it back. I am just going to live with it. 
>> 
>> If you find out what the problem is, let me know. 
>> 
>> Robert 
>> KG4KGL 
>> 
>>> On Sep 29, 2018, at 15:40, arsn4dd at charter.net wrote:
>>> 
>>> Is there an Omni V mechanic in the house? My radio is going to need
>>> one if it doesn't straighten up... HI HI 
>>> I have a very sparingly-used Omni V.9 that has developed an
>>> intermittent receive issue. From a cold start, the radio powers up and
>>> operates properly. After some random period of time, I can power cycle
>>> the radio, and as a result, I lose receive signals. I retain plenty of
>>> audio, and plenty of what sounds like band noise, but there no signals
>>> anywhere. I can leave the radio off for a couple of minutes, power it
>>> up, and the signals return. Before the suggestion is floated, I have
>>> exercised every connection in the radio with DeOxit. I have tightened
>>> and re-tightened every screw on every board in the radio. I have not,
>>> however re-seated any of the chips. Is there enough information here
>>> to generate suggestions? I admit to being mostly an appliance
>>> operator, but I might be capable of doing a few diagnostics. Thanks in
>>> advance for any guidance. 
>>> Best Regards to all!
>>> Dennis N4DD
>>> _______________________________________________
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>>> TenTec at contesting.com
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>>> 
>> 
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