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CMOY sounds extremely faint on both channels

post #1 of 9
12/10/09 at 3:07pm
Thread Starter 
Hi guys,

I've been following Tangent's CMOY tutorial, and am currently at the stage where I'm supposed to be testing the amp circuit, before I hookup the panel connectors like the pot/jacks/etc.

Because I don't have enough alligator clips, I've gone ahead to hookup one stereo mini jack to the circuit for testing purposes. Also, because I ordered 470uf caps with axial style leads by mistake, the circuit board is rather cramped and I need to take extra care to ensure that component leads aren't crossed.

My problem: I can hear very very faint sound in both the left and right earbud when I try to test this circuit. I have the source volume turned up to max. I have included photos of the front and back of my CMOY, and would appreciate it if you guys could take a look and advise me on how I should proceed with troubleshooting.

Thanks!
LL
LL
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post #2 of 9
12/11/09 at 3:35am
im a noob and still buidling mine when i get free time inbetween work, but my guess is the gain? which type of resisters did u use in the r4 and r3 position



Tweaks is what im basing my conclusion on, what type of headphones are you using? I lack alligator clips at the moment so my test will be the final test, heh
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post #3 of 9
12/11/09 at 3:53am
nihraguk,

Not sure where you are located, but if you can purchase some liquid flux and reflow the solder joints, you may have better success. Tangent has great tutorials on soldering techniques Tangent Tutorials . Some of the joints in the pic are "cold" solder joints. These joints may look fine but may not be conducting. See if that helps.

The flux can be put in a flux bottle (has a small needle on it) to put very sparingly amount at the solder joint. You will be surprised how well the solder flows.
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post #4 of 9
12/11/09 at 4:31am
Not to derail the thread but can lemon juice be used instead of flux? I've been reading this on a couple sites...
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post #5 of 9
12/11/09 at 1:54pm
I wouldn't try it when Flux is cheap and easily available in most areas.

Gain shouldn't be a problem. This sounds more indicative of bad joints - they need to be reflowed. No offense but they're pretty messy, and probably the cause (or one of the causes) of your problem here. For instance, joints on the same strip of copper should all flow together nicely to form a shiny, nicely rounded joint. The joint should not have a rough surface.

I second the suggestion for Tangent's tutorials, they're great.

It's also a possibility the opamp is damaged, but I'd fix the joint first as they're the more likely cause.
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post #6 of 9
12/11/09 at 2:12pm
Thread Starter 
Quote:
Originally Posted by Juaquin View Post
I wouldn't try it when Flux is cheap and easily available in most areas.

Gain shouldn't be a problem. This sounds more indicative of bad joints - they need to be reflowed. No offense but they're pretty messy, and probably the cause (or one of the causes) of your problem here. For instance, joints on the same strip of copper should all flow together nicely to form a shiny, nicely rounded joint. The joint should not have a rough surface.

I second the suggestion for Tangent's tutorials, they're great.

It's also a possibility the opamp is damaged, but I'd fix the joint first as they're the more likely cause.
I wasn't aware that joints on the same strip of copper should be congealed together to form a single joint... will get cracking on that now. Tried to build a CMOY on a stripboard instead, hoping that giving the components more space would help me to troubleshoot any problems; alas, now I have only one channel working. Posted my pictures/issues here for help: http://www.head-fi.org/forums/f6/cmo...ml#post6226261
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post #7 of 9
12/11/09 at 11:03pm
wait the entire strip should be connected together? i thought u just needed to get the contact secure with the copper around it, and the copper path does the rest...hmmz should be interesting to see what happens with mine then as well
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post #8 of 9
12/12/09 at 12:09am
Quote:
Originally Posted by igotyofire View Post
wait the entire strip should be connected together? i thought u just needed to get the contact secure with the copper around it, and the copper path does the rest...hmmz should be interesting to see what happens with mine then as well
You can use the pad alone, but if your there it wont hurt in small runs like the cmoy to flow them together. Makes a larger stronger joint. Will use more solder, but better than chasing cold solder joints later on.
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post #9 of 9
12/12/09 at 4:55am
Yes, technically individual points is fine. My point was that if you truly gave it enough heat and solder, they would all melt together - that's always how it happens for me. If they don't run together it probably means you didn't apply enough heat for long enough and the solder didn't wick properly. For reference, see Tangent's tutorial, specifically this picture: http://tangentsoft.net/audio/cmoy-tu...-underside.jpg
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