loud pop when turning pedals on/off - AKA - replacing capacitor on an active bass?

[polvo]

Sorry for a kind of cryptic subject line. I've been down a bit of a chatgpt rabbit hole trying to figure out what's going on here, but I don't know if I can trust what it's telling me. Think I need some human input on this one!

 

Problem: I get a loud pop when turning my pedals on or off. This is only on one particular bass. 

 

Likely cause (according to chatgpt): Output coupling capacitor is likely leaky or failing, causing DC leakage and popping. BUT My bass has nothing that looks like the replacement capacitor I found online (e.g. https://ebay.us/m/62aZgK). It's a Cort B4 Plus AS (wiring schematic here: https://www.cortguitars.com/wp-content/uploads/2024/07/cort-b4-plus-as-basses-schematic.pdf). 

 

My questions for the wise heads of basschat:

• Based on the tests I've done (listed below), is the capacitor likely the problem or is chatgpt hallucinating? If not, what else could I try?
• If I can't see a capacitor, does that mean it's likely build into the circuit board of the active electronics module? And if so, is that something I could realistically fix myself with basic soldering skills?

 

Tests I've done to identify the cause of the problem (summary by chatgpt):

• Measured DC voltage at output jack: ~1.75-2.0 V DC present with battery, 0 V without battery (confirms DC leakage).
• Battery voltage verified healthy.
• Output jack switching continuity: Functioning as expected, switches battery ground on connection.
• Push-pull active/passive switch continuity tested: Switch behaves correctly on both positions.
• Pickup resistance measured at circuit board inputs: Neck pickup ~3.25kΩ, bridge pickup ~9.2kΩ (normal ranges).
• Output coupling capacitor tested for DC leakage with multimeter: Resistance readings 0.3 MΩ and 0.046 MΩ, lower than ideal for a blocking capacitor, suggesting leakage.
• Battery connected vs disconnected test: DC leakage present only with battery connected, consistent with capacitor leakage causing DC to output.

Edited 2 hours ago by polvo