My Objective 2 Will Not Turn On

[jschristian44]

I tried to test my Objective 2 today which I completed and it would not turn on. When I removed the power cable once the red light turned on for a second but I cannot get it to turn on at all anymore. Please help! I have a multimeter but don't know how to troubleshoot this being my first amp, thanks!

[ethanolson]

Are you familiar with the troubleshooting guide? It's here: NwAvGuy: O2 Details

I'd also suggest a read of the section just prior, called "Initial DIY Testing."

[sofaspud]

Is this a "stock" build? What power supply are you using? Have you successfully performed any of the tests laid out by NwAvGuy in his O2 build blog? Check if you have DC both in-to and out-of the regulators with the amp turned off but power supply connected.

[billyk]

Can you post the voltage and resistance readings from the guide, that will be a good place to start.

[jschristian44]

Well I have a multimeter but I did not do any of those tests yet. Would those tests usually tell me what is wrong and then I can fix that part? Thank you!

The ones listed here right:

o2%2520resistances%2520no%2520power%255B3%255D.png (image)

I know where to put the red/black into the multimeter right now but that is all. Where do I set the Dial to on it to get readings for this chart? I have this multimeter:

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Thank you!

[billyk]

Ok great, that is the diagram you will need. For the meter, you will be using the ohm scale, the one on the lower left quadrant of the meter dial. You will use different ranges depending on what you will be measuring. Use a range that will be in the range of what you want to measure; for example the 100k or the 40k resistors would use the 200k range and the 270k would need to use the next range up, the 2M range. Place the probes, one on each end of the resistor you are testing and jot down the reading.

Before you start, check the board thoroughly for solder bridges and cold joints, use a magnifier, I find that helps to focus and see things you may miss otherwise.

Good luck!

Oh and I just thought, are the battery polarities correct? That's an easy mistake to make, I know I do it all the time

[jschristian44]

There is one thing called the Star Ground or something and it said to solder that bridge so I did. I don't understand it but it had metal on the bottom and I just filled it in considering they'd touch anyways. I didn't put batteries in this one, just plugged it in. Hopefully I can find out what is wrong!

[jschristian44]

Okay so I tested it and everything looked pretty fine. The only thing I can think of it being is the OPAMP legs. Two of them are pretty bad. One is bent badly which can be fixed but one is broke in half. I figured as long as it touches the metal prong on the side in the socket I got for them it should be alright. That is on all four amps, a total of 2 are pretty bad. But I made sure they touched the metal so it should be alright. As for the testing, the only one that seemed off was one that should have read 3.30 but read 3.96 on the 2M Ohm setting. That was a little too off for me I think as all the others were very well in the range they needed to be. That was for R25. I don't think that would explain it not turning on at all though. There is a bridge for the C9 and C8 points underneath that I filled in with solder. Was this correct or not? Thanks! Picture is attached so you can see measurements and their setting I used for it.

[agdr]

Originally Posted by jschristian44

The only thing I can think of it being is the OPAMP legs. Two of them are pretty bad. One is bent badly which can be fixed but one is broke in half. I figured as long as it touches the metal prong on the side in the socket I got for them it should be alright.

jschristian44 - no, the op amp legs do have to go down into the sockets. You will need to replace any of those op amps where the legs have broken off and won't go into the socket.

A tip here. The manufacturers bend the op amp legs out to be slightly wider than the sockets so they work properly in automatic insertion machines, for factory assembly. For DIY use you need to put the op amp on it's side with the pins down flat on a table, and then turn the op amp body to very slightly bend all the pins a few degrees so they are more up-and-down, so they fit well into the op amp sockets. Then do it again for the pins on the other side of the op amp. And if you don't have an anti-static mat (op amp are very static sensitive to handling) just lay out a sheet of tin foil and do the bending on that to prevent static damage. Use a test clip to clip between the foil and something like your watch to equalize potential (voltage) before handling the op amp, or at the least just keep one hand touching the foil while you mess with the op amp with the other hand, on the foil.

Here is a test to try. The op amps don't even have to be in the sockets for this one. Turn off the O2 power switch and take the voltage measurements I wrote up here for another fellow

The Objective2 (O2) Headphone Amp DIY Project

That will tell if your power supply is OK. To measure that put your black test probe wire in the middle "com" hole on your meter and the red test probe wire goes in the hole to the right of that, the Volt/Ohm/mA hole. Then turn your meter dial to "20" in the upper left area, the DC volts section. That will give you meter readings up to 20 volts DC.

Once we all know if your power supplies are OK the folks here can help you from there. And... get some new op amps on order!

[agdr]

jschristian44 - one more thing. You actually may want to hold off on ordering those new op amps until you find out why your LED isn't coming on. You may need to get a LED, too, or some other parts. There have been a couple of cases of bad LEDs. If you get +12V and -12V from that test in the link I posted, then when you turn the O2 power switch on (don't plug in any headphones until you get this part fixed) your LED should light, even if none of the op amps are installed. If it doesn't then the folks here can help you with more troubleshooting. The LED may be bad or there may be something else wrong.

I'm going to crawl back under my rock. Good luck!