[sdiy] Non-DIY, but looking for repair advice...

[MrHarry]

re: Idly curious
No. The meter is supplying the current that is reading the resistance, but anything that is still connected is still in the circuit.  If the meter voltage is high enough
it may even read some semiconductor junctions connected (that's why "diode" scales exist on multimeters) and the resistance you read can be different when you reverse the probe polarity.
Also, if there are capacitors (especially electrolytics) they will make the meter reading increase or decrease as the capacitor is charging.

Removing the part is the right advice.  If it is a two-lead device you can lift just one end of it (floating in midair) then you can read it.

Harry


-----Original Message-----
From: John <synth-diy at synth-diy.org>
To: David <dixon at mail.ubc.ca>
Cc: synth-diy <synth-diy at synth-diy.org>
Date: Monday, 28 October 2024 11:18 PM EDT
Subject: Re: [sdiy] Non-DIY, but looking for repair advice...


On Mon, 28 Oct 2024 19:58:54 -0700
David G Dixon <dixon at mail.ubc.ca> wrote:

> Hey John, my advice would be to carefully remove the offending
> trimpot from the board and then measure it.  Since it is connected to
> other things on the PCB, you really don't know what the actual
> impedance between any two legs should be, because the trimpot could
> be in parallel with other impedances on the board.
> 
> If it still reads wacky after you have desoldered it, then you were
> right. If it reads around 100k, then you still have some digging to
> do.

Hm, makes sense. (Idly curious, though, as I'm very much a novice at
low-level electronics - does that apply even if the power's off? The
only current flowing then should be between the two leads of my meter
on the two legs of the pot, correct?)
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