[TenTec] Omni VI frequency jumping/drifting

[k4mt1950 at charter.net]

I have been over entire PLL circuit and resoldered all the
connections. Also inspected entire logic board for bad solder. I think
the PLL circuit analog components are too temp sens. I could heat it
with hair dryer and see PLL control V start cycling. Blow air from a
fan on it and it stops. Again its a very small variation and you have
to look for it to find it. 
Freeze spray on individual components was inconclusive.

Gary K4MT

	-----------------------------------------From: "w0ep" 
To: tentec at contesting.com
Cc: 
Sent: Thursday June 28 2018 7:56:21AM
Subject: Re: [TenTec] Omni VI frequency jumping/drifting

 I don't disbelieve what you are saying... but I wonder if you've

 got a bad solder joint or other kind of physical crack somewhere,

 some capacitor has more or less capacitance depending on the temp

 expansion?

 On 06/28/2018 08:40 AM, k4mt1950 at charter.net wrote:
 > Stan:
 > I have had the exact same problem with my Omni VI. There is a
 > procedure to properly adjust band crystals. It is:
 > Omni VI Lock PulseRig should be on for at least 1/2 hour.Check
10MHz
 > REF at pin 9 of U12.Adjust 10MHz REF with C31.Check for lock pulse
at
 > pin 11 of U13, Scope probe on x10 position; .2 volts per div, and
.1us
 > time/div.Adjust L12 thru L21 on Xtal Osc. LO Mixer Bd. for the
 > narrowest wave form.
 > I did this but it did not help. I tuned in WWV and watched it on a
 > waterfall and you could see carrier drifting back and forth. I was
 > missing over half of the FT8 decodes as a result.
 > What I found is PLL circuit on logic board is very temp sensitive.
I
 > tried to locate a part but the entire thing is that way. I found by
 > putting a very small fin blowing across logic board completely
 > eliminated the drift cycling.
 > FT8 now works perfectly. Put the fan along the right side (looking
 > from front) and not back panel. Back panel heats up during TX and
when
 > I put my fan there the problem got worse when I went into TX.
 > Afraid its a design flaw and cant be fixed any other way.
 > Gary K4MT
 >
 > -----------------------------------------From: "Stan Gammons"
 > To: "Discussion of Ten-Tec Equipment"
 > Cc:
 > Sent: Wednesday June 27 2018 7:38:42PM
 > Subject: [TenTec] Omni VI frequency jumping/drifting
 >
 > Hi Everyone,
 >
 > My Omni VI has decided to throw a few more fits. First the
frequency
 > jumped on 30 meters, but FT8 signals still decode fine. So I let it
 > go
 > and didn't mess with it. Lately 40 meters has started throwing fits
 > and
 > it's much worse than 30 meters. Looking at the FT8 waterfall, at
 > times
 > it will drift during the 15 seconds and it's bad enough the FT8
 > signal
 > won't decode. I sent another email to the list with the waterfall
pic
 >
 > attached, but the message was too large and got rejected. I tried
 > tweaking the coils on the crystal oscillator board. It might have
 > helped 30 meters a little. Doesn't seem to have done much/anything
 > for
 > 40 meters though. Crystals gone bad maybe? If so, anyone know a
 > source
 > now that ICM is no more?
 >
 > 73
 >
 > Stan
 > KM4HQE
 >
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