[analogorgans] Re: SOS "Expression Pedal not working"
- From: Charles Strack <voceumana@xxxxxxxxx>
- To: analogorgans@xxxxxxxxxxxxx
- Date: Mon, 7 May 2007 13:48:15 -0700 (PDT)
NO--it's probably NOT shorted. Pots have 3
connections: top of the resistor, bottom of the
resistor, and wiper; connect between either top or
bottom and the wiper, and you get a variable
resistance; connect between the top & bottom of the
resistor and you get no variation at all.
Rodgers used the pots to drive a lamp, which was
closely coupled to a light dependant resistor (CdS
Cell) under a black cover. If the lamp burns out, no
variation in volume, so perhaps you've just got a
burned out lamp.
Rodgers used a couple of different style covers and
lamps, but it should be on the output board. It's
probably a #19 or a #24CS lamp, but I don't have the
manual so I can't say for sure. 19's are easy to come
by, but 24CS's are hard to find. If it turns out to be
that one, let me know, as I have a few spares I could
part with.
Charlie Strack
--- bh <lexicon13@xxxxxxxxxxx> wrote:
> Hi Gerald,
>
> Thanks for your quick reply. I
> followed your instructions
> and removed the cardboard enclosure that surrounds
> the expression pedal
> to get to the pot.
>
>
> Illustrations of test connections
> made:
>
>
> (Potentiometer)
> / | \
> / | \
> white/brown solid solid
> wire brown black
>
> \ wire wire
> \ / ^
> \ or / |
> \ / |
> \ / |
> [red test lead] [black test lead]
> | /
> | /
> |______________/_____
>
> OHMS meter
> _____________________
>
>
>
> I clipped the OHMS meter's Test-leads with the
> Black-test-lead on the
> potentiometer's black terminal/wire and the
> Red-test-lead to solid brown
> terminal/wire; I was able to observe a resistance
> variance reading on
> the OHMS meter's scale when I operated the
> expressions pedal up and
> down.
>
> I then removed the OHMS meter's Red-test-lead and
> clipped it to the
> White/Brown striped potentiometer's terminal/wire;
> with this connection
> I was not able to observe any resistance variance
> reading on the OHMS
> meter while operating the expressions up and down.
>
> So then, it's safe to assume the potentiometer is
> shorted and I have to
> replace it?
>
> Barry
> PS: I check the potentiometer for openings to spray
> it with the
> electronic cleaner and there were none; it was
> hermetically sealed.
>
>
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