Uploaded November 2024 | Updated September 2026, 1 week ago
Pioneer QX-747 “Pop” after turn on Fix
OK,
My challenge hopefully is your gain. Purchased a QX-747 for like nothing recently and cleaned it up. All four channels perform like a champ.
Except that when you turn it on within the first few minutes, there’s a loud “pop” and then the protection circuit kicks in, the audio goes mute, and then it comes back and you’re good for several hours. Until the next time you turn it on.
Search the Internet and went through multiple threads. While I’m sure this whole thing needs a recap and alignment outside of a regular amp DC offset and bias, I want to get this awful pop fixed.
Originally thought it would’ve been one of those really low microfarad blue drop capacitors in the tone circuit.
Nope, it’s one of the Sanyo D313 voltage regulators in the power supply.
Purchased a couple off of eBay and after a few days traveling from China, they arrived and I installed them tonight.
Receiver is working like a charm, and there’s no pop.  My bench top speakers also thanked me for the lack of a punch in the eye.
This is a quick throw together video, hope this works for you if this is your issue. I have reason to believe that this might be the same issue for other models that are non-quad from the 1974 era. 
Pioneer QX-747 “Pop” after turn on Fix
OK,
My challenge hopefully is your gain. Purchased a QX-747 for like nothing recently and cleaned it up. All four channels perform like a champ.
Except that when you turn it on within the first few minutes, there’s a loud “pop” and then the protection circuit kicks in, the audio goes mute, and then it comes back and you’re good for several hours. Until the next time you turn it on.
Search the Internet and went through multiple threads. While I’m sure this whole thing needs a recap and alignment outside of a regular amp DC offset and bias, I want to get this awful pop fixed.
Originally thought it would’ve been one of those really low microfarad blue drop capacitors in the tone circuit.
Nope, it’s one of the Sanyo D313 voltage regulators in the power supply.
Purchased a couple off of eBay and after a few days traveling from China, they arrived and I installed them tonight.
Receiver is working like a charm, and there’s no pop.  My bench top speakers also thanked me for the lack of a punch in the eye.
This is a quick throw together video, hope this works for you if this is your issue. I have reason to believe that this might be the same issue for other models that are non-quad from the 1974 era. 
