[cms5423]

Hey guys, I just finished soldering everything on, and wired everything up, and the amp isnt working. When I turn the pot on (it has a built in switch), the LED lights up, but I get no output. I attached two pics of my amp, and was wondering if someone could hop on AIM and help me out. My screen name is cmspearman02. Thanks so much

 

[Pars]

You don't appear to have anything in for R5... you need the jumpers or a small (47 ohm) resistor there, otherwise the feedback loop isn't completed, and no sound. Jumper them.

 

[cms5423]

oh wow, thanks soooo much!

 

[cms5423]

Ok, so everything is working now, except through my right channel, the audio is very muffled when compared to the left audio channel. Could this be my interconnect? Or what else could cause just one channel to be extra quiet, but still be clear? Thanks

 

[Pars]

Take a close (as in magnified) look at solder joints. Reflow any that look suspect (add a touch of solder). Also look for any bridges (solder bridging pads that should not be connected). I did not take a close look at the pics that you posted (they are a bit far away and not really clear enough to see anything in detail though).

 

[cms5423]

all the joints look ok, and I made sure to remove any bridges. What else could be a source of muffled audio out of one audio channel? Could it be a grounding thing? Or a burnt component such as a capacitor?

 

[Pars]

I would really doubt a component failure. Use a DMM and ohm it out, comparing the good channel to the bad. Pull the opamp and measure each pin of the socket to ground, as well as to the adjacent pins. L channel should match R channel. If not, figure out why and fix it. Check the jacks and solder connections on them as well.

 

[cms5423]

Ok, well everything is definitely soldered fine. The odd thing is that when i connect the left channel lead from the mini jack input to the pot, to the right channel audio output lead on the pot that sends the audio from the pot to the cmoy, it works fine. Wouldn't this mean that there is a problem from sending the audio from the mini input jack to the pot?

 

[Pars]

You are saying that if you take the L channel lead from the input jack to the pot, and touch it to the R channel pot to amp lead that the right channel works fine? This seems to identify the input jack to the pot as the culprit on the R channel?

What if you took the R channel lead from the input jack to the pot and did the same thing (to the L channel)?

 

[cms5423]

hmm, now i can't get the right channel to work at all again. What should I look for to identify a bad joint that I should reflow? Because there definitely aren't any bridges

 

[tangent]

Put a short mini-to-mini extension cable in the output jack, and measure resistance from each of the three contacts on the other end of the cable to the point in the circuit they should attach to. You should get nearly 0 ohms for all of them. If so, repeat for the input jack. Your symptom could be a damaged jack.

 

[cms5423]

Ok, the jacks are definitely working, it's something on board, but there are definitely no solder bridges, so it must be either a resistor, capacitor, the pot, or a bad solder joint. How could I identify a bad solder joint? Is there a chance the pot could be broken for only the right audio channel? What kind of problem would lead to audio going through the channel, just being muffled. Because that is the problem, the audio through the right audio channel is working, it's just super muffled.

 

[Gvvt]

It took me a couple of days to finally find a bad solder joint on one of the power supply resistors. It looked fine, but I found that if I pushed lightly on the resistor, I could see the stub of the lead moving where it stuck up above the solder. Keep checking; you'll probably find whatever it is.

 

[cms5423]

Wow, I can't thank you enough for all your help guys! Turns out, like most mistakes, it was so obvious. I had my one wire going from pot to the cmoy board soldered in a hole that was one row above where it should have been.

 

[cms5423]

One more quick question though. It sounds fantastic, except some high notes are hissy, what could cause that? Thanks again