KNS-80/KNI-520 encoder bad?

OK... question for those in the know. I've got a KNI-520 connected to a
KNS-80 RNAV. The DME, localizer, and RNAV *distance* work fine, but the VOR needle
doesn't deflect properly recently. If you try to center it, it won't stay in the
center, but rather will twitch from pegged on one side to pegged on the other with a
very small (5 degrees) change in the OBS ring. I'm thinking that since the head
doesn't have a NAV converter, but rather tells the KNS-80 where the OBS is with
encoder lines, that one of those lines might be broken/intermittent. That would mean
it would think the head is in 1 of 4 (2?) positions, rather than somewhere in between.

Thoughts on this? Anyone fixed such a thing? I haven't torn into the wiring
yet and suspect it's intermittent (read: difficult to find).

-Cory

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************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote:
OK... question for those in the know. I've got a KNI-520 connected to a
KNS-80 RNAV. The DME, localizer, and RNAV *distance* work fine, but the VOR needle
doesn't deflect properly recently. If you try to center it, it won't stay in the
center, but rather will twitch from pegged on one side to pegged on the other with a
very small (5 degrees) change in the OBS ring. I'm thinking that since the head
doesn't have a NAV converter, but rather tells the KNS-80 where the OBS is with
encoder lines, that one of those lines might be broken/intermittent. That would mean
it would think the head is in 1 of 4 (2?) positions, rather than somewhere in between.
Thoughts on this? Anyone fixed such a thing? I haven't torn into the wiring
yet and suspect it's intermittent (read: difficult to find).


I have this exact setup. I'm trying to remember, but I think mine got
twitchy at one point. If I remember correctly, it was mostly twitchy in
RNAV mode (as opposed to VOR mode). I think that's when I replaced my VOR
antenna, and it got a lot better. You're correct about the KNI-520 not
being a NAV converter. The KNS-80 send left/right signals to the head,
not composite video. Some of your other assertions may be valid, but
you'll have do dig into it before you'll know for sure. Good luck.

--- Jay



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Jay and Teresa Masino ___(_)___
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Check to see if your KNS80 has Mod 10 (should be stamped on the
back). I don't have the details, but this has to do with inter-
mittent contact between the internal circuit boards. Loose internal
contacts will produce the effects you mention. I found it cheaper
to buy a yellow tagged KNS80 on eBay than to fix my old one - but
it needed other repairs as well.

David Johnson

When I bought this from ebay awhile back, I checked on the mods. It
supposedly has 1-4 and 6-11 (I don't have it here in front of me). It just checked
out in June on the IFR certification (go figure!). I'm guessing it's one of the
connectors on the back.

It could be in the radio, but I doubt it's a bad VOR receiver/converter, since
the RNAV works. I think the radio's just not getting the right X/Y encoder signal
from the OBS knob, so it doesn't know where to put the needle.

-Cory

David Johnson wrote:
: Check to see if your KNS80 has Mod 10 (should be stamped on the
: back). I don't have the details, but this has to do with inter-
: mittent contact between the internal circuit boards. Loose internal
: contacts will produce the effects you mention. I found it cheaper
: to buy a yellow tagged KNS80 on eBay than to fix my old one - but
: it needed other repairs as well.

: David Johnson

--

************************************************** ***********************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Cory,

I would send U an indicator to try. Then I would know whether
the indicator worked. I'm not sure I can parse your email adx.

Bill Hale