[TenTec] Omni VI frequency jumping/drifting

[k4mt1950 at charter.net]

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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