Danelectro Backtalk, low volume issue

Started by Dimitree, August 12, 2023, 09:02:18 AM

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Dimitree

hi everyone,
I have a Danelectro Backtalk reissue that yesterday stopped to work properly: the output volume is now really really low, almost inaudible.
To understand the problem, I traced the circuit, and this is the schematic of the analog part.
I don't have the values for the capacitor since this pedal is using SMD parts.
I checked with an oscilloscope (1Vpp sine wave, 880Hz) and I found out that right after C1, the signal becomes as low as 15mVpp. On the output of the first opamp, the signal gets boosted to about 60mV.
Supply voltages are fine, 4.8V on the opamp pin 8 and 2.4V on the virtual ground rail.
Do you think C1 is the issue? or the signal is supposed to be lowered that much there, and the culprit could be elsewhere? Since this is SMD, before desoldering and swapping parts, I'd like to make sure about what could be the issue.
thanks!




MrStab

#1
Edit: if signal is reduced where you describe, then culprits are possibly C1 or R3 going open-circuit(ish), R2 shorting or op-amp being damaged to some degree.
Recovered guitar player.
Electronics manufacturer.

duck_arse

it's unlikely that opamp will be happy with 4V8 supply. is it a 9V powered pedal?
" I will say no more "

Dimitree

I replaced C1 with a 330nF capacitor and everything is fine again, thank you

duck_arse

Quote from: idy on August 12, 2023, 04:44:59 PM
People here die of sadness when they don't see voltages for all Qs posted every time things change. It is a custom here among the natives, we show each other our voltages as greetings.

what are those voltages now, to keep Idy happy?
" I will say no more "