Please help troubleshoot my ACA mini. It powers up, no smoke. I used my MP3 player with volume on max and I can barely hear sound coming out of amp. I mean the sound is very faint and can barely hear anything. These are the voltages for the left and right channels. All the pots are turned all the way counter clockwise. All the pots can't adjust any of the voltages no matter where the pots are turned to.
Left: VO to ground: 11.87V, VB to ground: 23.8V, VO to VB: 11.93V.
Right: VO to ground: 11.84V, VB to ground: 23.8V, VO to VB 11.97V.
I have no idea what's going on. What steps should I take to troubleshoot and diagnose?
Left: VO to ground: 11.87V, VB to ground: 23.8V, VO to VB: 11.93V.
Right: VO to ground: 11.84V, VB to ground: 23.8V, VO to VB 11.97V.
I have no idea what's going on. What steps should I take to troubleshoot and diagnose?
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take a look at active part are in the righ place ? maybe you mix the jfet ?
Q1 need to be the 170
Q2 the 74
Q4 the 520
Q5 the 9520
All caps negative -- look at the center of the pcb ? (only the super Farad C6 is reversed)
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@twoengine
It sounds like your not far away from having a working amp...having the proper reading from VO to ground. It seems your not following the proper biasing procedure as clearly spelled out under "Adjustment" in Nelson's original article located in post #1 of this thread. Don't go williy-nilly turning those pots until you understand the process.
This video might help:
It sounds like your not far away from having a working amp...having the proper reading from VO to ground. It seems your not following the proper biasing procedure as clearly spelled out under "Adjustment" in Nelson's original article located in post #1 of this thread. Don't go williy-nilly turning those pots until you understand the process.
This video might help:
Thanks for your help Nicoch and Kevin. Getting closer. I understand the VO and VB adjustment based on the pic and video.
This is where things stand now. Music is louder but very distorted.
VO is at 11.5V on both channels. I can only measure VB with only one probe on either the VB or pad next to it. If either probes touch VB and pad next to it at the same time voltage goes to zero. Also, VB is constantly changing fast anywhere from .15V to .35V. It's not a steady voltage like VO.
Please advise what to try next to get VB to test correctly with both probes on VB and pad next to it and have a steady voltage readout.
This is where things stand now. Music is louder but very distorted.
VO is at 11.5V on both channels. I can only measure VB with only one probe on either the VB or pad next to it. If either probes touch VB and pad next to it at the same time voltage goes to zero. Also, VB is constantly changing fast anywhere from .15V to .35V. It's not a steady voltage like VO.
Please advise what to try next to get VB to test correctly with both probes on VB and pad next to it and have a steady voltage readout.
Like the Mighty One says...post some pictures.even if I'm using my eyes on max, I can barely see anything on pictures you posted
It's standard procedure around here, if you ask for help you need to post pictures so we can see what you're working on.