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@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@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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