Odd KNS-80 Problem, looking for lore-based solution.

Ok, you avionics wonks, here's one for you. KNS-80 problem...

Around the time of installing the GPS, the groundspeed on the
KNS-80 began reading 00 KTS under all conditions while flying
BUT when pinged on the ground--in the aircraft--immediately reads
the correct value even with the test signal turned so low that the
DME can barely lock on.

This has happened in two different late sixties Bonanzas;
one 28v one 14v.

The 14v model had a KLN-90B installed, the 28v a 530W.
Both airplanes have TCADs, both have the KNS-80 talk-only
suppression line properly connected.

The DMEs both have great range, often seeing 80-100 mile locks
below 10,000 feet altitude MSL.

Things tried in flight that have no effect:

1. Stack of 4 KNS-80s rotated into the two airplanes: all
have same symptom. BTW, RNAV works on all.

2. Tune in VOR-DME stations in various directions, various
distances, various frequencies -- all lock but display 00KTS gs.
No Y channels 40us pings (.05 channels) tested.

3. RNAV tried, GS still 00KTS

4. All other radios turned off; no effect

5. All other radios REMOVED from stack... still 00 KTS

6. All other electrical loads shut off; Alternator shut off;
still 00 KTS

7. Various rpm and attitudes.

8. Can't listen to the DME audio in either installation.

Yet to try: Run the airplane while being pinged on the ground.
Expected result: Will indicate correctly.

The DME portion of the box has A+, an antenna, and the
suppression line coming into the box. How complicated
can this be? The DME sends serial distance pulses
internally to
the main 6800 processor (running at 0.95 MHz) where gs
is computed along with the trig for RNAV. (There are a lot
of external lines related to the VOR).

So what the heck can it be? Get rid of the Bonanza?

My plane is the 14v one; I've chosen to ignore the problem for
the last 5 years; the 28v one is being worked on by a local
shop whose customer is far more anal than I and wants it
fixed.

I called King and they are clueless. This one will take
a lore-based solution. I've written it up in detail, investigated
in detail but am missing something.

Am I being persecuted by MI5?

Bill Hale, Loveland CO

wrote:
Ok, you avionics wonks, here's one for you. KNS-80 problem...

Around the time of installing the GPS, the groundspeed on the
KNS-80 began reading 00 KTS under all conditions while flying
BUT when pinged on the ground--in the aircraft--immediately reads
the correct value even with the test signal turned so low that the
DME can barely lock on.

This has happened in two different late sixties Bonanzas;
one 28v one 14v.

The 14v model had a KLN-90B installed, the 28v a 530W.
Both airplanes have TCADs, both have the KNS-80 talk-only
suppression line properly connected.

The DMEs both have great range, often seeing 80-100 mile locks
below 10,000 feet altitude MSL.

Things tried in flight that have no effect:

1. Stack of 4 KNS-80s rotated into the two airplanes: all
have same symptom. BTW, RNAV works on all.

2. Tune in VOR-DME stations in various directions, various
distances, various frequencies -- all lock but display 00KTS gs.
No Y channels 40us pings (.05 channels) tested.

3. RNAV tried, GS still 00KTS

4. All other radios turned off; no effect

5. All other radios REMOVED from stack... still 00 KTS

6. All other electrical loads shut off; Alternator shut off;
still 00 KTS

7. Various rpm and attitudes.

8. Can't listen to the DME audio in either installation.

Yet to try: Run the airplane while being pinged on the ground.
Expected result: Will indicate correctly.

The DME portion of the box has A+, an antenna, and the
suppression line coming into the box. How complicated
can this be? The DME sends serial distance pulses
internally to
the main 6800 processor (running at 0.95 MHz) where gs
is computed along with the trig for RNAV. (There are a lot
of external lines related to the VOR).

So what the heck can it be? Get rid of the Bonanza?

My plane is the 14v one; I've chosen to ignore the problem for
the last 5 years; the 28v one is being worked on by a local
shop whose customer is far more anal than I and wants it
fixed.

I called King and they are clueless. This one will take
a lore-based solution. I've written it up in detail, investigated
in detail but am missing something.

Am I being persecuted by MI5?

Bill Hale, Loveland CO


If the DME distances read correctly, the problem is
inside the processor.

My KNS-80 also went wonky with slightly different symptoms.
The culprit was bad contact in the processor socket. If
there are socketed chips in your unit, try pulling and
re-socketing (with proper ESD strap on your wrist).

--

Tauno Voipio
tauno voipio (at) iki fi

: Around the time of installing the GPS, the groundspeed on the
: KNS-80 began reading 00 KTS under all conditions while flying
: BUT when pinged on the ground--in the aircraft--immediately reads
: the correct value even with the test signal turned so low that the
: DME can barely lock on.

: This has happened in two different late sixties Bonanzas;
: one 28v one 14v.

: The 14v model had a KLN-90B installed, the 28v a 530W.
: Both airplanes have TCADs, both have the KNS-80 talk-only
: suppression line properly connected.

: The DMEs both have great range, often seeing 80-100 mile locks
: below 10,000 feet altitude MSL.

: Things tried in flight that have no effect:

: 1. Stack of 4 KNS-80s rotated into the two airplanes: all
: have same symptom. BTW, RNAV works on all.

: 2. Tune in VOR-DME stations in various directions, various
: distances, various frequencies -- all lock but display 00KTS gs.
: No Y channels 40us pings (.05 channels) tested.

: 3. RNAV tried, GS still 00KTS

: 4. All other radios turned off; no effect

... including transponder? If the transponder is still on and doesn't have the DME suppression wired in it can wreck
havok with the DME (and consequently and distance/speed-related info).

: 5. All other radios REMOVED from stack... still 00 KTS

: 6. All other electrical loads shut off; Alternator shut off;
: still 00 KTS

: 7. Various rpm and attitudes.

: 8. Can't listen to the DME audio in either installation.

: Yet to try: Run the airplane while being pinged on the ground.
: Expected result: Will indicate correctly.

: The DME portion of the box has A+, an antenna, and the
: suppression line coming into the box. How complicated
: can this be? The DME sends serial distance pulses
: internally to
: the main 6800 processor (running at 0.95 MHz) where gs
: is computed along with the trig for RNAV. (There are a lot
: of external lines related to the VOR).

: So what the heck can it be? Get rid of the Bonanza?

: My plane is the 14v one; I've chosen to ignore the problem for
: the last 5 years; the 28v one is being worked on by a local
: shop whose customer is far more anal than I and wants it
: fixed.

: I called King and they are clueless. This one will take
: a lore-based solution. I've written it up in detail, investigated
: in detail but am missing something.

: Am I being persecuted by MI5?

: Bill Hale, Loveland CO

With swapping of multiple KNS-80's, it certainly seems odd. With *everything* else shut off (including transponders,
GPS's, etc) it should "just work" in all modes. I know when we got our KNS-80 we had a listing of all the mods possible and
some of them were fairly important. Maybe the ones you tried all were missing the same mods?

-Cory

--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

You didn't specifically say you tried it with the transponder off.
Could be the transponder isn't getting suppressed by the DME. There is
a signal into the transponder that is supposed to suppress the
transponder reply when it is activated. That line is supposed to be
connected to the DME so that the transponder doesn't step on the DME
return. If that line is unconnected, I think it will do what you are
experiencing if the transponder is active.

wrote:

Ok, you avionics wonks, here's one for you. KNS-80 problem...

Around the time of installing the GPS, the groundspeed on the
KNS-80 began reading 00 KTS under all conditions while flying
BUT when pinged on the ground--in the aircraft--immediately reads
the correct value even with the test signal turned so low that the
DME can barely lock on.

This has happened in two different late sixties Bonanzas;
one 28v one 14v.

The 14v model had a KLN-90B installed, the 28v a 530W.
Both airplanes have TCADs, both have the KNS-80 talk-only
suppression line properly connected.

The DMEs both have great range, often seeing 80-100 mile locks
below 10,000 feet altitude MSL.

Things tried in flight that have no effect:

1. Stack of 4 KNS-80s rotated into the two airplanes: all
have same symptom. BTW, RNAV works on all.

2. Tune in VOR-DME stations in various directions, various
distances, various frequencies -- all lock but display 00KTS gs.
No Y channels 40us pings (.05 channels) tested.

3. RNAV tried, GS still 00KTS

4. All other radios turned off; no effect

5. All other radios REMOVED from stack... still 00 KTS

6. All other electrical loads shut off; Alternator shut off;
still 00 KTS

7. Various rpm and attitudes.

8. Can't listen to the DME audio in either installation.

Yet to try: Run the airplane while being pinged on the ground.
Expected result: Will indicate correctly.

The DME portion of the box has A+, an antenna, and the
suppression line coming into the box. How complicated
can this be? The DME sends serial distance pulses
internally to
the main 6800 processor (running at 0.95 MHz) where gs
is computed along with the trig for RNAV. (There are a lot
of external lines related to the VOR).

So what the heck can it be? Get rid of the Bonanza?

My plane is the 14v one; I've chosen to ignore the problem for
the last 5 years; the 28v one is being worked on by a local
shop whose customer is far more anal than I and wants it
fixed.

I called King and they are clueless. This one will take
a lore-based solution. I've written it up in detail, investigated
in detail but am missing something.

Am I being persecuted by MI5?

Bill Hale, Loveland CO

On Aug 26, 7:28 pm, Ray Andraka wrote:
You didn't specifically say you tried it with the transponder off.
Could be the transponder isn't getting suppressed by the DME. There is
a signal into the transponder that is supposed to suppress the
transponder reply when it is activated. That line is supposed to be
connected to the DME so that the transponder doesn't step on the DME
return. If that line is unconnected, I think it will do what you are
experiencing if the transponder is active.



wrote:
Ok, you avionics wonks, here's one for you. KNS-80 problem...

Around the time of installing the GPS, the groundspeed on the
KNS-80 began reading 00 KTS under all conditions while flying
BUT when pinged on the ground--in the aircraft--immediately reads
the correct value even with the test signal turned so low that the
DME can barely lock on.

This has happened in two different late sixties Bonanzas;
one 28v one 14v.

The 14v model had a KLN-90B installed, the 28v a 530W.
Both airplanes have TCADs, both have the KNS-80 talk-only
suppression line properly connected.

The DMEs both have great range, often seeing 80-100 mile locks
below 10,000 feet altitude MSL.

Things tried in flight that have no effect:

1. Stack of 4 KNS-80s rotated into the two airplanes: all
have same symptom. BTW, RNAV works on all.

2. Tune in VOR-DME stations in various directions, various
distances, various frequencies -- all lock but display 00KTS gs.
No Y channels 40us pings (.05 channels) tested.

3. RNAV tried, GS still 00KTS

4. All other radios turned off; no effect

5. All other radios REMOVED from stack... still 00 KTS

6. All other electrical loads shut off; Alternator shut off;
still 00 KTS

7. Various rpm and attitudes.

8. Can't listen to the DME audio in either installation.

Yet to try: Run the airplane while being pinged on the ground.
Expected result: Will indicate correctly.

The DME portion of the box has A+, an antenna, and the
suppression line coming into the box. How complicated
can this be? The DME sends serial distance pulses
internally to
the main 6800 processor (running at 0.95 MHz) where gs
is computed along with the trig for RNAV. (There are a lot
of external lines related to the VOR).

So what the heck can it be? Get rid of the Bonanza?

My plane is the 14v one; I've chosen to ignore the problem for
the last 5 years; the 28v one is being worked on by a local
shop whose customer is far more anal than I and wants it
fixed.

I called King and they are clueless. This one will take
a lore-based solution. I've written it up in detail, investigated
in detail but am missing something.

Am I being persecuted by MI5?

Bill Hale, Loveland CO- Hide quoted text -

- Show quoted text -

Yup. The transponder was also removed from the rack.
The suppression is important on this setup because the
kns80 DME can suppress other boxes but has no suppression
IN. (In fact can be damaged if suppressed IN.)

And the really odd thing continues to be: The thing works perfectly
when interrogated by a test box on the ground. That eliminates
all of the things like the processor connections.

The suggestions to try seem to be to run the engine while
interrogating the thing on the ground; and to taxi toward
a vor while on the ground.

Totally confusing. Thanks for the read. Bill Hale

wrote:
: Ok, you avionics wonks, here's one for you. KNS-80 problem...

: Around the time of installing the GPS, the groundspeed on the
: KNS-80 began reading 00 KTS under all conditions while flying
: BUT when pinged on the ground--in the aircraft--immediately reads
: the correct value even with the test signal turned so low that the
: DME can barely lock on.

: This has happened in two different late sixties Bonanzas;
: one 28v one 14v.

: The 14v model had a KLN-90B installed, the 28v a 530W.
: Both airplanes have TCADs, both have the KNS-80 talk-only
: suppression line properly connected.

: The DMEs both have great range, often seeing 80-100 mile locks
: below 10,000 feet altitude MSL.

: Things tried in flight that have no effect:

: 1. Stack of 4 KNS-80s rotated into the two airplanes: all
: have same symptom. BTW, RNAV works on all.

Distance displays in both VOR and RNAV mode, but no GS, right? Does OBS work correctly?

: 2. Tune in VOR-DME stations in various directions, various
: distances, various frequencies -- all lock but display 00KTS gs.
: No Y channels 40us pings (.05 channels) tested.

: 3. RNAV tried, GS still 00KTS

: 4. All other radios turned off; no effect

: 5. All other radios REMOVED from stack... still 00 KTS

: 6. All other electrical loads shut off; Alternator shut off;
: still 00 KTS

: 7. Various rpm and attitudes.

: 8. Can't listen to the DME audio in either installation.

Is that normal or has it changed?

: Yet to try: Run the airplane while being pinged on the ground.
: Expected result: Will indicate correctly.

: The DME portion of the box has A+, an antenna, and the
: suppression line coming into the box. How complicated
: can this be? The DME sends serial distance pulses
: internally to
: the main 6800 processor (running at 0.95 MHz) where gs
: is computed along with the trig for RNAV. (There are a lot
: of external lines related to the VOR).

: So what the heck can it be? Get rid of the Bonanza?

: My plane is the 14v one; I've chosen to ignore the problem for
: the last 5 years; the 28v one is being worked on by a local
: shop whose customer is far more anal than I and wants it
: fixed.

: I called King and they are clueless. This one will take
: a lore-based solution. I've written it up in detail, investigated
: in detail but am missing something.

: Am I being persecuted by MI5?

: Bill Hale, Loveland CO

Just a thought, but is it possible that somehow the encoder lines to the OBS are messing with
things? The GS is computed as the arrival/departure speed to/from the waypoint (or VOR). If you're
flying parallel to the waypoint, it'll read 0GS. Is the newly-installed GPS using the same OBS head via
a switch/mux box?

My installation has a slightly flaky connection to the back of my KNI-520 head. One of the
resolver lines occasionally loses connection and then the head doesn't work right. It's impossible to
center the needle as it swings from full one side to full the other, 90 degrees off from what it
*actually* is. I've never noticed if the GS goes to hell, but I'd suspect it would. I think the
distance still reads right.

-Cory

--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

Problem with KNS-80 solved.

It happened when the swithbox disconnected the
indicator resolver to connect it to the GPS.

The KNS-80 didn't like that and flagged the groundspeed.

The reason it worked with the test box on the ramp is that
the VOR portion of the KNS-80 had no input. So there
was no 30hz reference signal and the box couldn't
detect that the absence of the resolver.

There is a fairly obscure note in the KLN-90B instruction manual
that mentions this; a jumper is required.

Bill Hale

wrote:
: Problem with KNS-80 solved.

: It happened when the swithbox disconnected the
: indicator resolver to connect it to the GPS.

: The KNS-80 didn't like that and flagged the groundspeed.

: The reason it worked with the test box on the ramp is that
: the VOR portion of the KNS-80 had no input. So there
: was no 30hz reference signal and the box couldn't
: detect that the absence of the resolver.

: There is a fairly obscure note in the KLN-90B instruction manual
: that mentions this; a jumper is required.

: Bill Hale

Cool! Congrats on finding that. Definately an obscure one.

-Cory


--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************

wrote in message
...
wrote:
: Problem with KNS-80 solved.

: It happened when the swithbox disconnected the
: indicator resolver to connect it to the GPS.

: The KNS-80 didn't like that and flagged the groundspeed.

: The reason it worked with the test box on the ramp is that
: the VOR portion of the KNS-80 had no input. So there
: was no 30hz reference signal and the box couldn't
: detect that the absence of the resolver.

: There is a fairly obscure note in the KLN-90B instruction manual
: that mentions this; a jumper is required.

: Bill Hale

Cool! Congrats on finding that. Definately an obscure one.

-Cory


--

************************************************** ***********************
* Cory Papenfuss, Ph.D., PPSEL-IA *
* Electrical Engineering *
* Virginia Polytechnic Institute and State University *
************************************************** ***********************



Good Job.

Al G