Well, I thought everything was going well. Now, there is distortion galore coming through the right channel. Meanwhile, the left channel is okay, just overpowered by this static grunge in the other channel that just came up. It is also worth mentioning that the grunge decreases a bit when I push the gain switch in between gain settings, meaning that at gain 0, the grunge is much more bearable but still quite present.
I made sure there were none of the common problems occurring like a voltage issue (double tested this, referring to both the "Initial DIY Testing" and "Step-By-Step DC" Voltages sections), the audio signal opamps (either of those three switched between positions gives the same result), and cold solder joints. My very layman, very noobish guess is it's U2, the power comparator, NJM2903D, sending transients into the power management circuitry, just based on a quirky process of elimination and a very wild, very uneducated guess.
At any rate, I am not measuring more than 4 mV DC offset, so I am at a total lost at what to do now. Once I get home tonight from a super easy exam, I will make a simple switcheroo with an extra NJM2903D and hope that does the trick. Until then, guys!
I made sure there were none of the common problems occurring like a voltage issue (double tested this, referring to both the "Initial DIY Testing" and "Step-By-Step DC" Voltages sections), the audio signal opamps (either of those three switched between positions gives the same result), and cold solder joints. My very layman, very noobish guess is it's U2, the power comparator, NJM2903D, sending transients into the power management circuitry, just based on a quirky process of elimination and a very wild, very uneducated guess.
At any rate, I am not measuring more than 4 mV DC offset, so I am at a total lost at what to do now. Once I get home tonight from a super easy exam, I will make a simple switcheroo with an extra NJM2903D and hope that does the trick. Until then, guys!
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That sounds like the gain switch problem. The left front leg of the switch case can make contact with a via near R21, causing right channel distortion. You can bend the leg slightly, or cut it shorter with diagonal cutters.
If it was a defective NJM2903D, the distortion would in all likelihood be heard in both channels.
If it was a defective NJM2903D, the distortion would in all likelihood be heard in both channels.
I'm reasonably confident the problem is not with U2, or any of the power supply section. Reason being is all the opamps, U1, U3, U4 all share the same power rail, so if there was a power supply problem it would effect them all. The fact your left channel is fine rules that out IMO.
The noise changing in relation to gain level is interesting, and implys to me the problem is either the input to the main opamp U1 (2068) or the opamp itself / solder connections. So yeah, what he said ^
And does the distortion level change with the volume control?
The noise changing in relation to gain level is interesting, and implys to me the problem is either the input to the main opamp U1 (2068) or the opamp itself / solder connections. So yeah, what he said ^
And does the distortion level change with the volume control?
Thank you, sofaspud! That is it. I should have re-read the comments section on the O2 details page. That leg is smack dab on the via. Why is that even there? Besides for parts compatibility and IO expandibility, it is practically in the very same spot as P2's leg. This is undoubtedly the best amplifier I have heard (I owned a premade O2 before and demoed too many $1K+ amps), and it has this silly via hanging out directly below it. I am surprised it did not make contact earlier.
So that visually looked like it could be the problem when it really wasn't at.
I played around with the insertion of the U1 opamp-it works if the opamp is just barely inserted. The pins are not connecting properly-the solder points are fine, but something is getting loose or disconnected in the socket whenever an opamp is inserted. In time, I will probably order a new opamp socket, along with new gain resistors and another switch, which I mistakenly cut and removed for testing. For now, it works-albeit as just a really nice buffer circuit.
I played around with the insertion of the U1 opamp-it works if the opamp is just barely inserted. The pins are not connecting properly-the solder points are fine, but something is getting loose or disconnected in the socket whenever an opamp is inserted. In time, I will probably order a new opamp socket, along with new gain resistors and another switch, which I mistakenly cut and removed for testing. For now, it works-albeit as just a really nice buffer circuit.
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O2 amp troubleshooting
Hey Guys, I just built a version of this amp based on the JDSLabs kit. I'm having an issue in that when I turn it on the LED lights up fine but I can't detect any current in the battery terminals using the DMM. Sorry if this question has already been asked but I can't seem to find anyone else with a similar problem.
Hey Guys, I just built a version of this amp based on the JDSLabs kit. I'm having an issue in that when I turn it on the LED lights up fine but I can't detect any current in the battery terminals using the DMM. Sorry if this question has already been asked but I can't seem to find anyone else with a similar problem.
Sorry, I wrote that in a hurry. Currently my amps LED lights up fine but when I measure the battery terminals (+ on bt1 and - on bt2) I get barely any voltage at all whether or not the AC adapter is in place. I was just wondering where to start testing or what the problem may be.
Correction, I get barely any voltage whether or not the SWITCH is in or out.
It sounds like a measurement error. Your DMM is set for DC volts?
Remove the batteries and measure each by itself. Put them back in and measure across + on bt1 and - on bt2 again.
Well the thing is I don't even have the battery terminals soldered in. I never intend to use batteries and I just left them out. The amp doesn't seem to work even with everything else soldered in and I can't seem to figure out why.
I haven't changed anything, as I said in my first post I've plugged in my AC adapter and the LED lit up when I would turn it on. In my second post I claryified that I was measuring the battery terminals as NWAguy reccommends here (under Initial Testing) and I don't get any voltage from AC or DC. Right now my O2 has everything but the battery terminals in it because I have no need for them (and I have an ODAC which fits nicely in there). My problem is that, when all the opamps are installed, I don't hear any sound and I believe that those two are related in some way.
Hopefully that sorts out any problems with understanding what my problem is.
OK.
Leave the O2 off for now, and use the good ground reference at BT1- for all these DC voltage readings. Measure the DC voltage at the positive lead of C2 and the negative lead of C3. Measure pin 1 of U5, then pin 3. Measure pin 2 of U6, then measure pin 3. Then each side of D1 & D5.
Post your results so we can verify that the power supply is operating correctly.
Leave the O2 off for now, and use the good ground reference at BT1- for all these DC voltage readings. Measure the DC voltage at the positive lead of C2 and the negative lead of C3. Measure pin 1 of U5, then pin 3. Measure pin 2 of U6, then measure pin 3. Then each side of D1 & D5.
Post your results so we can verify that the power supply is operating correctly.
Those aren't MOSFETs. Those are voltage regulators in a similar package as the real MOSFETs at Q1 and Q2.
If you look at the voltage regulators from the front, where the part number is printed, the pins are numbered 1-2-3 left to right.
The D1 & D5 voltages are not correct, so do leave the O2 turned off until we find what's wrong with the power supply.
If you look at the voltage regulators from the front, where the part number is printed, the pins are numbered 1-2-3 left to right.
The D1 & D5 voltages are not correct, so do leave the O2 turned off until we find what's wrong with the power supply.
There's the problem (hopefully the only one).
The inputs are fine, but you should have +12 and -12 volts at the outputs, not ~6 volts.
Give the board a good visual inspection - make sure the 7812 is correctly at U5, the 7912 at U6, there are no solder shorts, etc. Use the ohmmeter function of your DMM to make sure things are connected where they should be.
If everything checks good, it's likely one or both regulators are bad and need to be replaced.
If you read the past few days' posts in this thread, you'll see another builder also had a power supply problem. It turned out to be the 7912 negative voltage regulator. I mention this especially because when he was doing these voltage checks, there was no voltage drop across D1 & D5, just as you've found. It makes me suspicious of your 7912 regulator, but it's a good idea to look and see if you can find a problem visually before starting to desolder parts.
The inputs are fine, but you should have +12 and -12 volts at the outputs, not ~6 volts.
Give the board a good visual inspection - make sure the 7812 is correctly at U5, the 7912 at U6, there are no solder shorts, etc. Use the ohmmeter function of your DMM to make sure things are connected where they should be.
If everything checks good, it's likely one or both regulators are bad and need to be replaced.
If you read the past few days' posts in this thread, you'll see another builder also had a power supply problem. It turned out to be the 7912 negative voltage regulator. I mention this especially because when he was doing these voltage checks, there was no voltage drop across D1 & D5, just as you've found. It makes me suspicious of your 7912 regulator, but it's a good idea to look and see if you can find a problem visually before starting to desolder parts.