$429 Dimmer Switch

No reason, my sweet hiney. Some poor engineer that was overworked and
underfunded tried to make six components do four components work. Nothing
bizarre about it at all.

Jim


"Jay Honeck"
shared these priceless pearls of wisdom:

- Get in there and do that kind of thing yourself and pay somebody to check
-it
- and sign it off !
-
-Um, well, it took quite a while to determine that it was a problem with the
-dimmer itself.
-
-The circuitry for this thing is just totally bizarre. Rather than just
-being a simple rheostat, it's hooked into some transistors, and capacitors,
-and resistors -- all for no apparent reason.



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

You paid someone to change light bulbs?

The hotel must have a No Vacancy sign every night!

Even me, the software geek (I don't do hardware, I don't do
Windows) can change every light bulb (except 1 and that's the
bottom left on the panel) in and on the cherokee.

Tsk tsk tsk...

Now the dimmer switch is another matter entirely...

Jay Honeck wrote:
: $104 in parts, 5 hours labor (It's a real bitch to diagnose and get at in a
: Cherokee...).

You got a good deal. I paid $179 for the right hand dimmer switch in my
Cherokee 180's panel 2 years ago. Not including installation, which broke
within 1 hour because the mechanic (1) couldn't solder and (2) had no
notion of how to properly suppport soldered wires against vibration.

--
Aaron Coolidge (N9376J)

Wouldn't replacing an approved dimmer assembly with a home-made one be a
"major alteration" that would require a Form 337, and field approval of the
data, for return to service?

"Jim Weir" wrote in message
...
A WHAT? Read the title at the top of the 337 form. **MAJOR** repair.

Sheesh.

Jim


Ray Andraka
shared these priceless pearls of wisdom:

- Would have required a 337,


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

$104 in parts, 5 hours labor (It's a real bitch to diagnose and get at in a
Cherokee...).

Total: $429.73.

Gotta love aviation.

As a confirmed "lingerer" it broke my heart to hit the reply button, but as a
30+ year general aviation mechanic, ham radio hobby buff, and electronic hobby
tinkerer, I felt compelled to add my voice here. Any body that understands
that tranistorized dimming system (and its just not that complicated) SHOULD
KNOW to verify that the light chain is not shorted before sticking in a new
transistor. A short is about the only thing I've ever seen that will kill the
otherwise beefy 2N3055 transistor. I'm not trying to brag about my skills but
just stating facts.....I could have had that problem diagnosed in about 15
minutes and had the transistor changed in less than two hours....and I know
better than to try to light the lights before I correct the short in the light
chain.....'cause if ya don't.....guess what.....there goes another transistor.
Sounds like you need another mechanic...at least another one to deal with
electrical/electronic problems.

And to Mr. Weir......the 337 is for Major repair and Major ALTERATIONS. As
the chief inspector for a large repair station, if I see an aircraft for an
annual with some kind of aftermarket or home made dimmer system....it better
have a 337 associated with it....not because I'm a jerk or an a**hole, but
because that is what the regulations require. Unfortunately, if I ignore that
or miss that and the owner rolls the aircraft into a ball, even if it had
nothing to do with the accident, I could be in big trouble with the feds or
possibly be sued by the estate and loose every thing I've worked so hard for
these last 30 plus years. I've been the biz long enough to have seen that when
there is an accident with death or serious injury, the FAA and the lawyers go
after any body they can get their hooks into....and if I haven't towed the line
with the regulations, it could be implied that I have been neglegent in my job.

If you want to own and fly a certificated aircraft, then do so in accordance
with the regs, if you're a tinkerer and enjoy working on your own ship....and
more power to you, then build a home-built and any thing goes....even doing
your own yearly condition inspections.

Oh no! Someone having the audacity to disagree with King Weir!
That'll make him spit out his morning latte! Stand by for the flames.

Good points John, and I agree wholeheartedly, but can you expect every
A&P to fully understand each and every detail? I don't care to pay
for an A&P's education, but it's almost like saying that you obtained
your 30 years in a few months.


On 13 Mar 2004 12:31:27 GMT, ospam (JohnN3TWN)
wrote:

As a confirmed "lingerer" it broke my heart to hit the reply button, but as a
30+ year general aviation mechanic, ham radio hobby buff, and electronic hobby
tinkerer, I felt compelled to add my voice here. Any body that understands
that tranistorized dimming system (and its just not that complicated) SHOULD
KNOW to verify that the light chain is not shorted before sticking in a new
transistor. A short is about the only thing I've ever seen that will kill the
otherwise beefy 2N3055 transistor. I'm not trying to brag about my skills but
just stating facts.....I could have had that problem diagnosed in about 15
minutes and had the transistor changed in less than two hours....and I know
better than to try to light the lights before I correct the short in the light
chain.....'cause if ya don't.....guess what.....there goes another transistor.
Sounds like you need another mechanic...at least another one to deal with
electrical/electronic problems.

And to Mr. Weir......the 337 is for Major repair and Major ALTERATIONS. As
the chief inspector for a large repair station, if I see an aircraft for an
annual with some kind of aftermarket or home made dimmer system....it better
have a 337 associated with it....not because I'm a jerk or an a**hole, but
because that is what the regulations require. Unfortunately, if I ignore that
or miss that and the owner rolls the aircraft into a ball, even if it had
nothing to do with the accident, I could be in big trouble with the feds or
possibly be sued by the estate and loose every thing I've worked so hard for
these last 30 plus years. I've been the biz long enough to have seen that when
there is an accident with death or serious injury, the FAA and the lawyers go
after any body they can get their hooks into....and if I haven't towed the line
with the regulations, it could be implied that I have been neglegent in my job.

If you want to own and fly a certificated aircraft, then do so in accordance
with the regs, if you're a tinkerer and enjoy working on your own ship....and
more power to you, then build a home-built and any thing goes....even doing
your own yearly condition inspections.

You paid someone to change light bulbs?

Well, not directly. They just replaced them (and the missing blue
condom-thingies that go over them) while they were there.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Good points John, and I agree wholeheartedly, but can you expect every
A&P to fully understand each and every detail? I don't care to pay
for an A&P's education, but it's almost like saying that you obtained
your 30 years in a few months.

My A&P is the best engine and airframe man I've seen.

However, when it comes to electrical, even he will admit that he's a "figure
it as you go" guy, even though he works on DC-9s most of the time.

Personally, I think the dimmer circuitry in the Cherokee is perhaps the
dumbest thing I've seen in aviation. Even I, as a total neophyte, can see
that the system is hopelessly obtuse.

Strangely, older Cherokees had a much simpler dimmer circuit. I wonder why
Piper made it so complex later on, and I wonder if they've corrected this
mess in their new planes?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

Jay,

I have one of those older dimmer systems, and it is no picnic. The old one is
just a power rheostat wired in with the lights. The rheostat heats up because
it handles all the power. That transistor circuit simply controls the current
by using the transistor to amplify small current changes in the rheostat. The
result is the rheostat needn't be a custom high power one, and it won't burn out
as easily. The rheostat only dimmer gets hot to the touch if you have more than
just the original overhead light and compass light on it, and probably can't
handle a full panel worth of lighting. I'd trade the simple older dimmer for
the transistorized one if it we cheap and painless to do. When my dimmer does
go, or I add more lighting to the panel, I'll probably opt for one of the pulse
width modulated ones (those are much more complicated than the piper pass
transistor, but they also dissipate very little power).

Jay Honeck wrote:

Good points John, and I agree wholeheartedly, but can you expect every
A&P to fully understand each and every detail? I don't care to pay
for an A&P's education, but it's almost like saying that you obtained
your 30 years in a few months.

My A&P is the best engine and airframe man I've seen.

However, when it comes to electrical, even he will admit that he's a "figure
it as you go" guy, even though he works on DC-9s most of the time.

Personally, I think the dimmer circuitry in the Cherokee is perhaps the
dumbest thing I've seen in aviation. Even I, as a total neophyte, can see
that the system is hopelessly obtuse.

Strangely, older Cherokees had a much simpler dimmer circuit. I wonder why
Piper made it so complex later on, and I wonder if they've corrected this
mess in their new planes?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

--
--Ray Andraka, P.E.
President, the Andraka Consulting Group, Inc.
401/884-7930 Fax 401/884-7950
email
http://www.andraka.com

"They that give up essential liberty to obtain a little
temporary safety deserve neither liberty nor safety."
-Benjamin Franklin, 1759

Ray Andraka wrote:

When my dimmer does go, or I add more lighting to the panel, I'll
probably opt for one of the pulse width modulated ones (those are
much more complicated than the piper pass transistor, but they also
dissipate very little power).

The next step in the evolution is to get rid of all those incandescant
bulbs and replace them with LEDs. Lower power consumption for the same
light output, and they never burn out.