[TenTec] Omni VI audio problem

[Stan Gammons]

Hi Bob,

One thing I forgot to check before and I pretty sure I found out what 
the problem is.  I have the PC soundcard out connected to the audio in 
on the back of the radio so I can use it for digital modes.  Seems as 
though it's picking up hash from the PC and it's getting mixed with the 
audio from the mic. When I disconnect the cable from the PC, things are 
normal.  Dang it!  Guess I need to put another or more ferrite cores on 
the audio cable.  I hear the computer hash when I test PTT with WSJT-X 
too.  So it's transmitting a cruddy digital signal too.  That's 
unacceptable.  I have to fix that.


73

Stan
KM4HQE

On 9/17/2018 8:51 PM, Bob McGraw K4TAX wrote:
> Stan:
>
> First I suggest turning the speech processor OFF and forever leave it 
> OFF.    If you want to use it, just remember,  more is worse.
>
> Even though the mikes worked on the TR7, I view this is no indication 
> the wiring is correct for the Omni VI.  I suggest checking the manual 
> for the correct mike wiring and physically confirm the mike of choice 
> is wired correctly.    I find mike wiring standards to be as varied as 
> dust particles in a Texas sandstorm.
>
> Pin #1 is mike high or mike audio
>
> Pin #2 is ground and shield.  Be sure the shield of the mike cable 
> also folds back into the Amphenol cable connector to make contact with 
> the shell.
>
> Pin #3 is PTT
>
> Pin #4 is  +4 DCV for use with an Electrect mike.
>
> Check the plug in filters on the bottom to see they are seated 
> correctly and correct location.  Again, contact cleaning of their pins 
> might be in order.
>
> One other test, disconnect the mike, turn the MIC gain fully 
> counterclockwise {off}, transmit and listen to the radio.  With the 
> 2nd receiver, tune across the frequency and listen for carrier.  In 
> general all should be quiet.  If you hear significant carrier, there 
> is a procedure to null the carrier.  Probably need an oscilloscope and 
> dummy load to do that.
>
> Next would be to check the frequency of the BFO crystals.  Again there 
> is an alignment procedure.  This must be adjusted in the exact steps 
> outlined in the manual as there is interaction between the 
> adjustments.  Repeat the procedure a couple of times.   A frequency 
> counter is required for this adjustment.  Don't skip one step just 
> because you don't intend to use that mode.  There is interaction 
> between the adjustments.
>
> And of course my last suggestion, which normally is my first 
> suggestion..........take time to pull each cable, using a Q-Tip 
> moistened with contact cleaner, scrub the male pins of each and every 
> connector.  Then plug and unplug the connector  a couple of times so 
> as to wipe the female contacts. Do this one at a time and double check 
> to see each connector is inserted fully and correctly.
>
> NEVER NEVER NEVER spray anything into the radio.   {One fellow I know 
> [not me] removed the plugin IC's, sprayed into their sockets, and now 
> he has a radio full of issues and weirdness.   Remember contact 
> cleaner is used to promote the flow of current.   Imagine what takes 
> place in a logic IC socket that is wet with cleaner. ugh!!!! }
>
> With a radio of that age, it not at all unusual for the electrolytic 
> caps in the audio stage to deteriorate.  One issue which can exist is 
> the output of a stage can drift negative a few millivolts.  In effect 
> it will reverse polarize the coupling capacitor.  The result is after 
> time the 1 MFD cap will migrate to about 0.01 MFD.  Not a good path 
> for audio in these circuits. Makes the radio sound funny too.     I 
> always replace the audio coupling capacitors with nonpolar 
> electrolytics of the same voltage and C value.   There is no need to 
> change parameters. Problem solved.  I had a lengthy discussion with 
> Tentec management and engineering on the subject some years ago.   It 
> almost caused me to not buy a new Omni VI Plus.    Finally, I did and 
> loved it.
>
> Hope this helps.
>
> 73
>
> Bob, K4TAX
>
>
> On 9/17/2018 8:00 PM, Stan Gammons wrote:
>> Hi All,
>>
>> I was tinkering with an old D-104 T-UG8 that I had put a Heil 
>> conversion kit in since the original element bit the dust. I ask for 
>> an audio report from some of the locals that know what I sound like 
>> and they said I sounded terrible.  So, I switched to the Ten-Tec 707 
>> mic, same report. So, I tried my trusty old EV-638. Same story.  I 
>> didn't try it with the converted D-104 to see what it sounds like. 
>> They initially told me it sounded like the mic was picking up 
>> something like a fan maybe, so turning the gain down helped a little 
>> but not a lot. SO, today I decided to put the Omni VI on a dummy load 
>> and listen to it with my Drake TR7.  Yuck! The Omni VI sounds 
>> terrible!  It's almost like there is a little bit of a carrier and it 
>> has what sounds like digital hash on it. It gets worse the higher the 
>> mic gain is cranked. When I modulate, the audio sounds all distorted. 
>> Even without modulation, if I turn the processor on and crank it up, 
>> the digital hash in the audio seems to get even worse. SO, just to 
>> make sure it wasn't something weird going on, I did the same thing 
>> with the TR7.  I put it on a dummy load and listened to it with the 
>> Omni VI. I tried it with the same mics and the audio is clean. No 
>> hash or anything.  Anyone heard of a problem like this with an Omni VI?
>>
>>
>> 73
>>
>> Stan
>> KM4HQE
>>
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>
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