[d00dz]

Alright here it goes...I built my first amp 2 days ago on a simple breadboard to check everything out at first. Everything worked, sounded great. Up to until yesterday were the right channel stopped working. I rebuilt the amp and rebuilt it again...triple checked the input/output wires to the jacks. Did the continuity testing everywere possible....matched all of the resistors perfectly for both channels. I'm using the OPA2132PA from Digi-Key. I'm using one rechargable battery but it worked when the amp worked and i've also recharged it numerous times to see if that is the problem.

Here are the values on the circuit:
Battery : One Ni-MH (Energizer, 150mAH) = 7.26v

Output from the "power supply" : V+ = 3.72v, V- = -3.69v

Values from virtual ground to opamp(negative at ground, positive at amp):
1: 0v
2: 6.46v
3: 3.86v
4:-3.47v
5: -13.9mV
6:-3.4mV
7: 0v
8: -7.34v

These values were taken from Tangents Op-Amp tester site:
http://tangentsoft.net/elec/opamp-tester.html

I've read numerous web sites into simple troubleshooting and the most recent posting with the PIMETA problem with left channel only. But don't understand.

Any help and troubleshooting in simple terms would help, becuase i dunno what DC offset voltage etc. is....

Thanks

 

[aeriyn]

Did you have the headphone plugged all the way in? =P

That was robzy's problem with his PIMETA.

 

[n_maher]

I'm just a noob like yourself but when I had problems with my CMoy it was very helpful when I posted pictures of the amp itself. Another member was able to spot my problem w/in a matter of minutes.

Not saying yours is that easy, but you might give it a shot if you can.

Now based on my limited experience and the chronology of your problem I'd suspect the jack or the cable your using. Have you tested to make sure that something isn't internally wrong with it? You should be able to hook your mini/mini to it and test resistance on the +/-/g. You didn't say that you'd already done that and it's my best guess.

Good luck and don't let it get you down.

Nate

 

[d00dz]

It's not the battery (i used a 9v wall adapter)
It's not the jacks, since i flipped the left and right input and then only the right side worked.
I used a different source (D-NE900) same problem.
And i used a different mini-mini cable...

You think the opamp fried or something? How do i check if the opamp is dead with a multimeter?

And i don't have a digital camera, sorry

 

[eipromb]

I've had that problem with a Chu Moy before, it turned out that I had soldered the gnd and right channel wires the wrong way on the input and output.

 

[gsferrari]

Why dont you just swap op-amps?

Post pics of the board and everything...more pics and better detail will make it easier to debug. Seeing that you dont have a digital camera -

Hard to tell without pics. From where I am and with what info I have on hand :-

* Bad Op-Amp
* Loose Ground Wire
* check input/output jacks especially the ground connections
* check connections on the pot - change the pot - bad pots can also be a problem.

 

[d00dz]

Quote:

Originally Posted by gsferrari Why dont you just swap op-amps? Post pics of the board and everything...more pics and better detail will make it easier to debug. Seeing that you dont have a digital camera - Hard to tell without pics. From where I am and with what info I have on hand :- * Bad Op-Amp * Loose Ground Wire * check input/output jacks especially the ground connections * check connections on the pot - change the pot - bad pots can also be a problem.

I don't have another opamp (I only ordered one off of Digi-Key), so how do i check through the multimeter if the opamp is shot? I'm using the OPA2312PA.

I've rebult the circuit many times, since it is on a breadboard.

I've checked and double checked the input jacks....ommitted the jacks completely using alligator clips, so the jacks aren't at fault.

After the problem i've taken off the pot thinking it was that, but it wasn't, so i've ommitted the pot, switch, and R5 from the circuit...

 

[robzy]

Quote:

Originally Posted by aeriyn Did you have the headphone plugged all the way in? =P That was robzy's problem with his PIMETA.

Lol, that was half my problem, as the problem existed earlier, but i didnt realise it was fixed as my headphones werent all the way in.

Rob.

 

[d00dz]

I think i have tracked down the problem, both of my 220uF Caps don't work and only because i put one of them in the wrong way (negative side from battery had same orientation as positive side)...I guess i never noticed from tangents .pdf file since the + and - are so small.
So hopefully buying new caps will work.

 

[d00dz]

Never mind the caps aren't the problem....I went and bought a pair of 220uF caps and installed them but I still get the same problem. (My multimeter can't read radial caps or something? It can read the 100uF caps fine). I've rebuilt the cMoy for the fourth time now....however i do hear VERY quiet music comming from the other side...

 

[gsferrari]

Op-Amp

Have you tried another one in its place yet? I think you should start there...

 

[d00dz]

Yeah, that's the problem, I don't have another opamp to see if it is the problem...I went to an electronics surplus store but they had nothing resembling OPA2*** so i didn't buy any.

Is there any way to determine if the opamp is at fault using my multimeter...such as DC offset (whatever that means)?

Thanks for you help

 

[gsferrari]

you can check op amp. do you have a bread board?

Set it up - give it input - measure output - check the gain

you will need a dual power supply and another supply for the input.

Cheers!

 

[Earwax]

Have you tried tangent's troubleshooting page? http://www.tangentsoft.net/audio/trouble.html Especially the part about tracing the audio signal through the amp.

Also, those voltages in the first post, is that still what you're getting? Pins 4 & 8 should be the supply voltage. at + & - half of the battery voltage.