Cherokee battery box repair

writes:


So far there's one vote for aluminum, one for stainless, and one for tin, eh?

No titantium or fiberglas?


Speaking of that, anyone figured out the purpose of the diode and resistor
back there on that vintage PA-28? As near as I can tell from the schematic, it allows
the alternator to slowly charge a completely dead battery with the master off.
Then will allow the alternator/partially charged battery to close the master and
charge it properly. Of course all this would require the alternator to self-excite...
something I didn't think they were typically set up to do. Thoughts?

If the soft core of the armature retains some flux, it may well self excite.

--
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

John Kunkel wrote:
: I was thinking of the collapsing field around the master contactor solenoid.

The way it's configured, it wouldn't do that either.

-Cory


--

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

I'll respond to my own post and a few others with the results.

- I believe my version of the Service Manual wasn't quite so descriptive on the
"Alternator source power circuit" label... it was pretty vaguge.

- I wasn't sure how sensitive the external regulator was to low bus voltages...
whether or not it would self-excite. The only self-exciting alternators I've played
with are the standard Delco GM (GM-10 or something?) that would be hung off a '78
pickup or equiv.

- It certainly seems like the box is tin, so one would think that if it were clean
enough regular Pb/Sn solder would stick. I was unsuccessful last night, but about the
only soldering I do is electrical in nature, so I didn't have any acid-based flux.
The Rosin core beaded up and wouldn't stick, as expected. A buddy of mine had a
rod of "magic solder" from when he did his box. Looked like a stick welding
rod with florescent orange flux. Took a hot-ass flame to melt it, but when it did it
bonded the copper/tin together nicely.

-Cory

--

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

If it is for the external connection, then it is there to prevent the
external power from activating the master or external power solenoid
from energizing if the external source polarity is reversed.
Michelle

wrote:

Another good idea, but the schematic has rather clearly shown the
diode/connector setup for the external connection, but has it shown as "optional."
This diode/resistor is in addition to that.

nrp wrote:
: I don't know Cherokee electrics, but does it maybe offer a way to (very
: slowly) charge the battery thru the external service plug?

: My Cessna 172M has a funny diode-resistor circuit like that in the
: battery circuit in which that's the only reason I can see for it. It
: is not described in the POH or even the service manual. Otherwise with
: a completely dead battery, if I used the ground service plug to start
: it, there still wouldn't be anything in the battery to initialize the
: alternator.

: Flyback diodes don't usually have a resistor in series with them.

OK, David. As a matter of fact, the Battery Box in my Seneca is made of
fiberglass. No titanium, though.
"David Lesher" wrote in message
...
writes:


So far there's one vote for aluminum, one for stainless, and one for
tin, eh?

No titantium or fiberglas?


Speaking of that, anyone figured out the purpose of the diode and
resistor
back there on that vintage PA-28? As near as I can tell from the
schematic, it allows
the alternator to slowly charge a completely dead battery with the master
off.
Then will allow the alternator/partially charged battery to close the
master and
charge it properly. Of course all this would require the alternator to
self-excite...
something I didn't think they were typically set up to do. Thoughts?

If the soft core of the armature retains some flux, it may well self
excite.

--
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