[TenTec] Omni6+ (564) intermittent problem

[John Bohnovic]

Jack,

Thanks for the update. I have the same problem with my Omni VI Plus 
and it is intermittent. The action you took will probably fix my 
rig's problem when I get around to opening up the box.

73 and again, thanks for the info..de John/K4WJ


At 07:36 PM 8/15/2008, you wrote:
>The Omni6+ intermittent problem that I posted on Friday Aug 8 appears to
>be fixed.
>
>FWIW, on Monday I removed the plate on which the NB and FM boards are
>mounted, to access the XTL osc/L.O. board.  All cables to the XTL
>osc/L.O. board were then disconnected and the board was removed.  I
>should add that before removing the NB and FM board, I verified by scope
>that the L.O. ouput for 15/12M was indeed intermittent.  All solder
>connections associated with the shared 15/12M L.O. output filter were
>then reflowed.  Although several of the solder joints looked suspicious,
>I couldn't positively identify any cracks or opens.
>
>Since the radio has been operating flawlessly all week since I did the
>work, I'm hopeful that the reflow operation fixed an intermittent solder
>joint.  Although at first I was a bit apprehensive about working on this
>buried board, TenTec's excellent labeling of cables and connectors
>quickly relieved my fears.  I took photos along the way, but found that
>they were not required to put things back together again; the pictures
>in the manual were sufficient.
>
>Jack K1VT
>
>
>______________________________________________________
>
>To: <tentec at contesting.com> Subject: [TenTec] Omni6+ (564) intermittent
>problem From: "Jack Mandelman" <modeler at bellsouth.net> Reply-to: Jack
>Mandelman <modeler at bellsouth.net>, Discussion of Ten-Tec Equipment
><tentec at contesting.com> Date: Fri, 8 Aug 2008 20:14:55 -0400 List-post:
><tentec at contesting.com">mailto:tentec at contesting.com>
>
>The other day I decided to check for propagation on 15M, and was
>surprised by how unusually quiet the band sounded; even the infamous
>21.333MHz birdie was not to be heard!  I then discovered that the
>maximum key down power output was about 2 watts, with very little
>sensitivity to RF output control setting.  12M exhibited the same
>symptoms, but the 564 operated normally on all other bands.  After about
>15 minutes the receiver abruptly returned to life and TX output was
>normal, on both 15M and 12M.  This intermittent was repeatable for every
>one of the several times I checked the rig from a cold start.  The
>problem has not been observed after the rig is warmed up.
>
>Based on the symptoms and examination of the schematics, I suspect an
>open in the bandpass filter for the L.O. output on the XTAL osc/L.O.
>mixer board.  12 and 15 meters share the same filter for the L.O. output
>before L.O. signal is sent to the BPF/front end board.  The symptoms may
>indicate an open in this filter.  I expect that the switching diodes
>(D38 and/or D43) to the filter are not blown, since diodes usually fail
>permanently in an open or shorted condition; an intermittent internal to
>a diodes is very rare.  I would like to reflow all the solder
>connections associated with the L.O. filter served by these diodes.
>
>My question is how to best access the XTAL osc/L.O. mixer board.  Has
>anyone had experience with accessing and removing this board?  I believe
>it is under the FM and LL driver/NB boards.  Haven't yet removed the
>covers to look at this problem. When I do, I will take many photos of
>the disassembly along the way.
>
>All comment/suggestions are appreciated.
>
>Jack, K1VT
>
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John Bohnovic
bohnovic at att.net
(352) 463-1822 house
(352) 284-8593 cell