Bugle 2 Faint/Dead Channel - diyAudio
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Old 1st October 2014, 02:35 AM   #1
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Join Date: Sep 2013
Default Bugle 2 Faint/Dead Channel

Hey everyone,
So I built my Bugle 2 over the weekend, pretty stock except for using the TO-99 version of the LM4562 opamps. Anyway, I plugged the unit into my system yesterday and was getting no sound over the right channel. I'm a novice and this is my first diy build so I went back and cleaned up my work a little bit, there were a few cold and starved joints. I plugged it back in after that and I can hear a faint tinny sounding remnant of music coming through the right channel now, almost like it isn't being amplified or equalized at all. When I unplug the working channel a signal at that same level comes through on both speakers. I've tested the channel for continuity and it looks fine. I've tested the voltages across that channel and they seem to be within the proper range. I've tested the voltage legs of the op amps and they look good, as well as testing the op amps input and output pins on that channel for continuity (and I swapped them out with the dip8 opamps just to be sure). No luck. Any ideas? Jim suggested a solder bridge might be the source, but I've looked the board over multiple times and can't find anything.
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Old 1st October 2014, 07:44 AM   #2
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Actually I think this should be in the analog source forum...
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Old 2nd October 2014, 07:35 AM   #3
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I know this is probably an unsafe way to test this, but I've discovered by pressing my finger on the solder side of the pcb that there is no feedback noise when I touch the rca jack pin, when I touch the resistor at r1r, when I touch the input loading resistor at r2r, but when I touch r3r (a 1.3k ohm resistor) I get a feedback noise. I took the resistor out and tested it and the resistance looked fine (around 1.29k ohms). I've already tried replacing the resistor at r2r but I haven't tested the resistance of either one I've had at that position (I'll do that tomorrow just to make sure I haven't put in two doa resistors in a row, but it seems unlikely). Anyone have any other ideas on what I should try next? Could it be a pcb defect?
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Old 2nd October 2014, 07:38 AM   #4
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I've also tried swapping out the film caps from channel to channel with no change. Tomorrow I will try swapping the electrolytic caps and see if that makes any difference. I'm convinced that the result of my caveman testing must mean something though and that the problem is somewhere between r2r and r3r.
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Old 2nd October 2014, 12:56 PM   #5
ittien is offline ittien  Viet Nam
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Join Date: Aug 2011
Though if you can take a picture clear enough so people can help out if any wrong resistor. I just built and it work.
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Old 2nd October 2014, 08:24 PM   #6
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Click the image to open in full size.
I'm pretty sure the resistors are all in the correct positions but anyone feel free to have a look. The ones at r2 are 61.9k for custom impedance loading.
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