While recapping this Crosley:
http://www.nostalgiaair.org/PagesByModel/566/M0003566.pdf

I noticed the tone control pot R-44 wiper had no connection ever soldered to it.... yet the schematic indicates that the wiper MUST be connected to ground in order to work. ...however the tone pot is working perfectly fine.
HOW can this be I ask myself??

...and the other components r-15, c34 are properly connected at one end of the pot and C-25 is connected correctly at the other end... but the wiper has nothing connected to it!!
I couldn't believe this or understand how this i working!!
So...I un-soldered everything from the pot and ohm-tested the wiper to each end... all is ok!!
What a puzzle!

How could the pot be controlling that circuit with the wiper floating in the air..with NO wires connected to it???

THEN..... after almost believing in magic... I remembered having seen this once before last year sometime...SURE ENOUGH... solved.

The pot is actually made with the wiper electrically common to the body and mounting hardware!!!!

... so the fact that the pot was mounted to the chassis (ground)... there was no need for a wire.!!

AAARrrrrrrrgggh !??
Why would any manufacturer EVER do this?

I think you should start a weekly post called the adventures of Pete. You do bring out many case histories that are helpful to others. Thank you.

anon

:While recapping this Crosley:
:http://www.nostalgiaair.org/PagesByModel/566/M0003566.pdf
:
:I noticed the tone control pot R-44 wiper had no connection ever soldered to it.... yet the schematic indicates that the wiper MUST be connected to ground in order to work. ...however the tone pot is working perfectly fine.
:HOW can this be I ask myself??
:
: ...and the other components r-15, c34 are properly connected at one end of the pot and C-25 is connected correctly at the other end... but the wiper has nothing connected to it!!
:I couldn't believe this or understand how this i working!!
:So...I un-soldered everything from the pot and ohm-tested the wiper to each end... all is ok!!
:What a puzzle!
:
:How could the pot be controlling that circuit with the wiper floating in the air..with NO wires connected to it???
:
:THEN..... after almost believing in magic... I remembered having seen this once before last year sometime...SURE ENOUGH... solved.
:
:The pot is actually made with the wiper electrically common to the body and mounting hardware!!!!
:
:... so the fact that the pot was mounted to the chassis (ground)... there was no need for a wire.!!
:
:AAARrrrrrrrgggh !??
:Why would any manufacturer EVER do this?
:
:
:
:
:

Well, if there is a way to make potentiometers with a body connection that's simple and inexpensive (just a little extra metal to a stamped piece), they'll probably do it because it saves a wire, which saves time and labor and money.

Thomas

Then why also bother to create a perfectly normal-looking and yet not to be needed wiper connector on the top with the other two connectors??

.. seems like the pot should look somewhat differently than a normal pot if it is built differently.
.. it certainly cannot be used for other "normal" potentiometer uses that do not require a grounded wiper!!!
How is one supposed to know which pot is and which pot is not case grounded to the wiper... geeze o'mighty.

Looks normal but is not?..

that's like marrying a woman and finding out she's a man... oops... right?

it anin't fair I say... lol

:Then why also bother to create a perfectly normal-looking and yet not to be needed wiper connector on the top with the other two connectors??
:
:.. seems like the pot should look somewhat differently than a normal pot if it is built differently.
:.. it certainly cannot be used for other "normal" potentiometer uses that do not require a grounded wiper!!!
:How is one supposed to know which pot is and which pot is not case grounded to the wiper... geeze o'mighty.
:
:Looks normal but is not?..
:
:that's like marrying a woman and finding out she's a man... oops... right?
:
:it anin't fair I say... lol
:
:
Peter,

I suppose manufacturers can be considered a whole nother critter. Have to save money anywhere they can in production. If the short wire to connect the wiper of the pot to chassis cost say 1/10 cent and 100,000 sets were produced, could add up to a good bit of pocket change. Eliminating a minute or two in wiring the set could could add up in cost savings.

Radiodoc

I fully understand the cost savings.
.. all I'm saying is that if it is different functionally internally it should somehow indicate that.

Yeah, I don't know why they don't remove the wiper, then. I suppose the pot could still be used with the wiper if the shaft was insulated from the chassis. Could also be, though, that the ring that the wiper contacts is a standard ring, like they all are, with a terminal attached. It may have cost them more money to make a stamper that would make the ring without the terminal. The price might have been more than the money they would have saved by not including the terminal. So.....they make one ring with a terminal, and another little gizmo that will connect this to the shaft if necessary. Too bad they don't indicate on the control whether the wiper is grounded or not, but you can find out quickly enough with your ohm meter.

I first encountered such a thing on my Philco 60. I could not understand why the low end of the volume control wasn't connected to the chassis.....and yet it still worked. Well, the low end IS connected to the chassis, but not via the terminal. It has an internal connection.

Thomas