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I tried to build a CMOY myself but I failed.. Anybody could help with trouble shooting?

  1. Korbear
    First, here comes my reference...
    http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=cmoy2_prj.htm
     
    I'm completely a beginner. I want to build a amp for my SR80, I've been searched a lot and ordered the matiarials online. After I got those, I build it immediately. However, after I finished...
     
    My Cmoy doesn't work right. When I set it up, I can ONLY hear a little base.. nothing else. As I adjust the potentiometer  to higher resistance, the sound goes crazy. It's all loud noise, no music. After I adjust futher, it went totally quiet.[​IMG]
     
    I've been very careful not to make mistakes when I was making it. I'm pretty sure there's no problem with soldering (altho I'm not an expert, I've been measured with a multimeter and there's no short cuts) The opamp was supported with normal voltage as well. The wire(22 gauge, way too thick, what gauge could be ideal for CMOY project?) and electrical tape that I used have no problem. So I am thinking maybe my design has problems ( I didn't make many changes compare with the original design). Also I might used my parts in the wrong way.
     
    I would be so appreciated and happy if anyone can trouble shoot it for me. I'm so stucked with it right now! So help me please! [​IMG]
     
     
     
    My design: (input and output are both grounded, not on the design tho[​IMG])
    IMGP2675.jpg
     
    Other pics that might help
     
    IMGP2673.jpg
     
    IMGP2674.jpg
     
    IMGP2676.jpg
     
    IMGP2668.jpg
     
     
    PS: There's no R5 on my amp. The potentiometer I used in my project was Panasonic EVJ-C20 10 kΩ.
     
    Thanks a lot!!!
     
  2. b0klau
    did you make sure the you inserted the opamp the right way? the side of the opamp with pin 1 (denoted with a dot) goes on the notch side of the ic socket. You could have shorted the opamp by inserting it the wrong way. 
     
  3. Korbear


    Quote:

    I double checked the direction of my opamp, there's nothing wrong with it. thanks for notice! If someone can make sure the design is right, i'll probably desolder everything and use thinner wire to do it again. Like I said, I've been reaaaaly careful when I was making it, because it's my first time making portable amp. That's why I believe the design has problem. I don't wanna waste my time redo it with a wrong design. So.. anyone could tell that the design is right (or not) I'll be appreciated![​IMG]
     
  4. sprocket87
    I'm new to this too but I'm getting ready to build my first Cmoy and your schematic looks right to me. But again, I'm no expert.
     
    Did you test this on a breadboard before soldering the PCB? Would be good to test it that way to verify the design works before soldering it.
     
    Maybe you could narrow it down. When you check voltage going into the op-amp were you reading 4.5V on each rail like you expect? If not then the problem is in the PSU somewhere, it would seem. 
     
  5. civilmonkey
    carefully carefully check for solder bridges (where the solder might accidently overflow onto another pcb pad), yup, check the v+ and v- going to the op amp, , and check tangentsoft.net for the CMOY article and trouble shooting tips.
     
    besides being a bit of a pain to work with, nothing wrong specifically with 22 gauge. 
     
    what op amp are you using?  some require a minimum gain to be sample so you could check that.
     
    op amps can fry too, say if you shorted something while testing with a multi meter, put it in backwards, had a solder bridge in the wrong place.
     
     
  6. Korbear
    Sprocket87: it's sweet to hear the design is right.. lol.. I didn't test it before soldering. But, how can you test it without solder it first? The thing I used was breadboard not a pcb, can't keep the wire in the right position. Is there really a way to test before soldering? I mean, i've never heard of it...
     
    Civilmonkey: The solder bridges look ugly I know but there's no short cut. Because it's the first thing that I've worried about and I've checked twice. The opamp I used was opa2132(TI). It's a high performance opamp it could work with a terrible votage supply. Actually, working with the 22 gauge is extremely painful to me. It's horrible.. but I don't have a better gauge. I can hold one single wire and lift up the whole thing. It's way to strong, almost hurt my hand when I tried to bend it. (Now I use the edge of my desk) What is the ideal gauge could be, if don't mind me asking?
     
    Im thankful for your help! both of you.[​IMG]
     
  7. sprocket87

    No, you used perfboard not breadboard. Breadboard is a bigger plastic board full of rows of holes that are connected together. So youd have two columns of say 5 holes each that are electrically connected underneath the plastic. Then you stick in your components and connect them to each other based on the schematic. You can also use wire jumpers and alligator clips to connect distant components together.

    Nothing has to be soldered which is why it's great for prototyping.

    Did you gets chance to ccheck the voltage going into the opamp with a meter?
     
  8. sprocket87
  9. Pars Contributor

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