Cherokee Strobe Noise

In article , Jonathan
Goodish writes:

I have a Cherokee with factory-installed wing tip strobes. I have an
original (1977) King Silver Crown avionics package, including audio
panel, KX170Bs, etc. I also have a Sigtronics panel-mount 4 place
intercom that was installed at some point before I purchased the
plane... I believe it is a SPA-400.

Everything is fine, except that the wing tip strobes can be heard like a
siren in the headsets. The siren sound is also occasionally transmitted
over the radio when we make transmissions, because I have been told to
"check my ELT" after making transmissions. Here are my observations:

I had this problem and I fixed it by adding a capacitor across the 12 volt
input at the high voltage power supply and placed a choke ahead of the input
(nearer the battery). My power supply is in the tail and the cap/choke killed
the high freq at the source.
Chuck

Whelen told you all that. Strange, they mark the case as "Not Field
Repairable" and then they let their techs violate their own rule. The
FAA police would surely frown. Their lawyers would squirm quite a bit
also. If you ever crash, have your family sue Whelen for $50 million
because the plane obviously crashed because of their "negligence" in
giving you "defective" repair information. My cut for this advice is
only 30%...

Mike

Ron Rosenfeld wrote:

On Wed, 27 Oct 2004 00:43:50 GMT, Jonathan Goodish
wrote:


Everything is fine, except that the wing tip strobes can be heard like a
siren in the headsets.


Sounds like a problem I have had with a Whelen power pack.

Can you hear the sound at the power pack? I could.

When I called Whelen, I was told that the problem was a bad capacitor.
They told me which capacitor to replace. I replaced it and it worked fine
for a few years, although the noise is just now starting to come back.

The power pack, however, is riveted closed. So I had to drill out the
rivets, replace the electrolytic capacitor, and put the box back together.
Took about 10 minutes on the phone with Whelen tech support; 30 minutes of
labor and a $2.30 capacitor. Needed some pop rivets, too, to put the box
back together.



Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

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Jonathan Goodish writes:


Everything is fine, except that the wing tip strobes can be heard like a
siren in the headsets. The siren sound is also occasionally transmitted
over the radio when we make transmissions, because I have been told to
"check my ELT" after making transmissions. Here are my observations:


Has it always been that that way; or has it be getting worse?

In either case, I'll add another. Clean and check the battery
connections and any/all engine/alternator ground straps. BOTH ENDS.
You typically have a ground lug that's connecting to a dissimilar
metal; that's corrosion city.

Why does it matter? Well, the battery is [also] a whopping big
capacitor; you want low impedence connections to it.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On 28 Oct 2004 02:40:04 GMT, Mike Spera wrote:

Whelen told you all that. Strange, they mark the case as "Not Field
Repairable" and then they let their techs violate their own rule. The
FAA police would surely frown. Their lawyers would squirm quite a bit
also. If you ever crash, have your family sue Whelen for $50 million
because the plane obviously crashed because of their "negligence" in
giving you "defective" repair information. My cut for this advice is
only 30%...

I will accord your advice a value equal to less than what I paid for it.

Even in jest, it is an attitude that I find distasteful, although I can
understand from where you are coming.

The option for Whelen to repair the unit did not exist (due to its age),
nor do I recall any such marking on the case.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

On 29 Oct 2004 22:31:42 GMT, Mike Spera wrote:

But, if Whelen won't do the repair and will still offer repair
assistance, they are better than many outfits that just tell you to buy
a new unit. Good to hear you were able to get it working.

I don't know if the assistance was company policy or one technician trying
to help out. There was no hemming and hawing, so I tend to believe it was
company policy at that time.

The repair was done about 7 or 8 years ago. At *that* time it was over 30
years old. During the past year or so I'm starting to hear a very faint
"siren", but not anywhere as annoying as when I fixed it.

Pretty good return on investment.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

In article ,
Jonathan Goodish wrote:
Everything is fine, except that the wing tip strobes can be heard like a
siren in the headsets. The siren sound is also occasionally transmitted
over the radio when we make transmissions, because I have been told to
"check my ELT" after making transmissions. Here are my observations:


Thanks to everyone for your suggestions. I believe that I have located
the main problem right now, which is a local ground at the intercom
jacks in the front panel. The jacks were supposed to be installed using
insulating washers, with a central ground. It looks like the avionics
shop may have done it that way, but then someone replaced the insulating
washers on some of the jacks (but not all of them) with huge lock
washers at some point after the system was installed. After trying
other suggestions, I decided to focus on the intercom system and pulled
the jacks from the panel... the strobe noise (and every other noise)
immediately disappeared when the local ground was broken.

Now, I need to find somewhere to get insulating shoulder and flat
washers, unless someone has another interim solution. Radio Shack
doesn't carry that kind of stuff any more, and don't seem to be able to
find any local retail electronics shops. Don't know whether Lowe's or
Home Depot would carry stuff like that or not, but I doubt it.



JKG

Jonathan Goodish writes:


Now, I need to find somewhere to get insulating shoulder and flat
washers, unless someone has another interim solution. Radio Shack
doesn't carry that kind of stuff any more, and don't seem to be able to
find any local retail electronics shops. Don't know whether Lowe's or
Home Depot would carry stuff like that or not, but I doubt it.


DigiKey

3069K-ND may be the right number.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

In article ,
David Lesher wrote:
Now, I need to find somewhere to get insulating shoulder and flat
washers, unless someone has another interim solution. Radio Shack
doesn't carry that kind of stuff any more, and don't seem to be able to
find any local retail electronics shops. Don't know whether Lowe's or
Home Depot would carry stuff like that or not, but I doubt it.


DigiKey

3069K-ND may be the right number.

Thanks, I believe that I can find the appropriate parts there. Only
problem is, they're showing an end-of-November ship date. I can
probably fabricate something for the interim if I end up ordering from
them.



JKG

Jonathan Goodish wrote:
: Thanks, I believe that I can find the appropriate parts there. Only
: problem is, they're showing an end-of-November ship date. I can
: probably fabricate something for the interim if I end up ordering from
: them.

If you order new jacks from one of the aircraft supply houses they usually
come with insulating washers. If the jacks are 10 years old you could
proably use new ones anyway, as the springiness of the contacts is probably
mostly gone. I ordered some from Chief aircraft and they were $5 or so for
the jack, washers, nuts, etc.
--
Aaron Coolidge

In article ,
Jonathan Goodish wrote:
Thanks to everyone for your suggestions. I believe that I have located
the main problem right now, which is a local ground at the intercom
jacks in the front panel. The jacks were supposed to be installed using
insulating washers, with a central ground. It looks like the avionics


It looks like I spoke too soon, maybe. After looking a the Sigtronics
instructions again (pulled from their web site), it looks like they _do_
recommend a local ground for the headphone jacks, and a central ground
for the mic jacks. Therefore, Sigtronics only supplied insulating
washers for the mic jacks, and the headphone jacks were grounded locally
as directed in the instructions.

My question is, could this still be my problem? Should I go to the
trouble of pulling the airplane apart and running the headphone ground
back to a central point, or is something else most likely the culprit?



Thanks,
JKG