$429 Dimmer Switch

Err, that transistor is there so that the rheostat doesn't double as a space
heater. It is there for a very good reason, although today there are better
ways to dim rather than a pass transistor. For that price, you could have
installed one of the pulse width modulated dimmers and done away with the old
fashioned piper circuit. Would have required a 337, but then it would be the
last time you'd ever have to deal with it. You might have even been able to
get separate dimmer circuits for instrument and overhead lights out of the
deal.

Jay Honeck wrote:

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. At first the shop thought it
was one of the transistors, but it blew instantly when they installed a new
one (at no charge to me), so they had to keep digging.

Mumble, grumble. Stupid 30 year old planes. I'm sure the new Cirrus panel
has everything in the dimmer circuit on a single chip, hidden somewhere in
the armrest, or something.
--
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

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

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

I've been answering this same exact question for thirty-three years exactly the
same way, and I'm not going to go into the song and dance here again. You can
google the answer if you like, or you can download Applications Note 1 (the one
I wrote back in 1972 as amended through last year) from www.rstengineering.com
if you want the long answer.

Or, I can reproduce it here if you all would like some flame bait.

Jim


"Dan Thompson"
shared these priceless pearls of wisdom:

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

OK, I did what you said. I read your App. Note 1. Also googled around for
other things you have written. I guess I still don't "get it."

Your App. Note 1 references an AC that was superseded back in 1996, AC
20-62C, which is now AC 20-62D. The current version says in the definition
of "Acceptable Parts": "(2) Parts produced by an owner or operator for
maintaining or altering their own product and which are shown to conform to
FAA-approved data." So how can an owner's home-made dimmer circuit can be
installed without any approved data?

You have cited the "Chief Counsel" on several occasions. Do you mean, by
any chance, the "Assistant Chief Counsel for Regulation letter dated Aug. 5,
1993 " referred to in http://www.awp.faa.gov/new/fsdo/ans_jan2_98.htm? I
would like to see that letter, if you know anywhere that it is published.
Unless it is publicly available, it would be hard for someone to cite it as
an authority.



"Jim Weir" wrote in message
...

I've been answering this same exact question for thirty-three years
exactly the
same way, and I'm not going to go into the song and dance here again. You
can
google the answer if you like, or you can download Applications Note 1
(the one
I wrote back in 1972 as amended through last year) from
www.rstengineering.com
if you want the long answer.

Or, I can reproduce it here if you all would like some flame bait.

Jim


"Dan Thompson"
shared these priceless pearls of wisdom:

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

Ya know, this has all been great fun, but a huge time sink. I'll take the
thread up again next weekend, but I won't waste valuable engineering time with
folks who have an honest difference of opinion. Opinion, mine as well as yours,
are like assholes...everybody has one and most of them stink.

See ya after hours...

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

I don't have an opinion. I just want to learn. Come back and cast some
more pearls ....

Meanwhile, I did find out a couple more semi-official FAA opinions:

http://www.faa.gov/avr/afs/news/arch...2002/Parts.htm

http://150cessna.tripod.com/obrienonownermadeparts.html

Again, the gist seems to be that owner made parts have to be based on
approved data of some kind. The owner can't just roll his own, no matter
how much better it is, without a field approval.

"Jim Weir" wrote in message
...
Ya know, this has all been great fun, but a huge time sink. I'll take the
thread up again next weekend, but I won't waste valuable engineering time
with
folks who have an honest difference of opinion. Opinion, mine as well as
yours,
are like assholes...everybody has one and most of them stink.

See ya after hours...

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

Ray Andraka wrote:

Err, that transistor is there so that the rheostat doesn't double as a space
heater. It is there for a very good reason, although today there are better
ways to dim rather than a pass transistor. For that price, you could have
installed one of the pulse width modulated dimmers and done away with the old
fashioned piper circuit. Would have required a 337, but then it would be the
last time you'd ever have to deal with it. You might have even been able to
get separate dimmer circuits for instrument and overhead lights out of the
deal.

Be a bit carefull with PWM dimmers., if they get placed near the avionics
you might have problems with RFI .

Have a look at the circuitry for the alternator-fail annunciator
on the Piper Arrow. It wastes 4 watts just to keep a globe off.
(I'd always wondered why the comm-panel switches were always hot)