[sdiy] Blown LF13741 and suitable replacement?

[Ingo Debus]

> Am 01.02.2026 um 04:09 schrieb Michael E Caloroso via Synth-diy <synth-diy at synth-diy.org>:
> 
> I would be MUCH more concerned with the 102VAC potential between shield and ground before replacing that opamp.  Or even operating tha rogue device, that is a lethal electric shock waiting to happen!!

That’s most probably the Y capacitors in the speaker’s power supply. Remember, a modern voltmeter has a very high impedance, so you’ll measure some high voltage between live and ground even with a quite low capacitance in series with the voltmeter. If the DMM can measure AC current, measure the current from the audio cable to mains ground (same as when you measured the voltage, but DMM in AC current measure mode). I’m willing to bet that the current is so low that there’s nothing to worry about (but if it’s not so low, you should indeed not use that power supply anymore).

I just picked randomly one of the class II SMPS wall warts here and measured both AC voltage and current from its output to mains ground. Voltage is 80 volts but the current is only 0.06 mA.

Probably this leakage current wasn’t the reason for the fried opamp at all.

Ingo
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