Mini3: second time around and problems
May 7, 2009 at 5:38 PM Post #16 of 37
Ok, here you go:

DC offset
Set meter to 2000m DB Voltage and get the following:
Black probe on IG and red probe on OG = 0
Black probe on IG and red probe on OL = 0
Black probe on IG and red probe on OR = 0

DC offset
Set meter to 20 DB Voltage and get the following:
Black probe on IG and red probe on OG = 0
Black probe on IG and red probe on OL = 3.62
Black probe on IG and red probe on OR = 0
 
May 7, 2009 at 5:47 PM Post #17 of 37
Ah, so sorry about my bad advice. The AD8397 opamp is certainly fried. It explains the excessive current drawing and the audible clicks. I hope you weren't using any expensive headphones, that is what I'm worried about. 3.6V is a lot for a headphone.
 
May 7, 2009 at 5:52 PM Post #18 of 37
Nope... I know just a little to know not to use good headphones when in first use. I used crappy ones.

How do you know it is the AD8397 opamp and not the OPA690ID?

I'm guessing that the opamp must have been bad/defective... Any way of knowing if it was something that I did? I've done engough cmoy's to know how to solder and all. I know think it was excessive heat.
 
May 7, 2009 at 5:58 PM Post #19 of 37
Yeah I don't know how the ground opamp will deal with the extra voltage. On my M³ when I had significant offset on the ground channel, both channels of my headphone would be affected with massive bass loss. I don't understand how the 3-channel works yet.

If there are any joints that aren't soldered properly or bridging, you can reflow all of them. Reflow the AD8397 pins too. My M³'s problem I believe was due to a loose opamp.
 
May 7, 2009 at 6:05 PM Post #20 of 37
Quote:

How do you know it is the AD8397 opamp and not the OPA690ID?


The DC offset numbers you posted suggest the ground channel op-amp is functioning normally.

Quote:

DC offset
Set meter to 2000m DB Voltage and get the following:
Black probe on IG and red probe on OG = 0


 
May 7, 2009 at 6:11 PM Post #21 of 37
So testing IG & OG is testing DC offset for the OPA690ID?

IG & OL and IG & OR is testing DC offset for the AD8397?

I appologize foe the questions... I am trying to learn.

MisterX, does my testing show the the AD8397 opamp is crispy fried? Or is still possible that I have bad soldering going on? While I have reflowed everything else, I haven't touched the opamps.
 
May 7, 2009 at 6:22 PM Post #22 of 37
It can be possible that it's just bad soldering. Your AD8397 is basically half working. We should focus on the parts with the L (like R1L, L1L (the ferrite cylinder bead), etc). Focus on AD8397's pin 5, 6, and 7 as well.

Yes to your questions.
 
May 7, 2009 at 6:24 PM Post #23 of 37
Quote:

Originally Posted by ShinyFalcon /img/forum/go_quote.gif
It can be possible that it's just bad soldering. Your AD8397 is basically half working. We should focus on the parts with the L (like R1L, L1L (the ferrite cylinder bead), etc). Focus on AD8397's pin 5, 6, and 7 as well.


Is there a pin layout anywhere? I know where pin 1 is due to marking on top of the opamp.

I wanted to thank you for your time in helping me...


Edit: I found a pin layout. Pins 1-4 are one side and 5-8 are on the other. Pin 1 is the where the mark on top of the opamp is located.
 
May 7, 2009 at 6:30 PM Post #25 of 37
Yep.
The OPA690 is the ground channel op-amp.
The AD8397 is the left and right channel op-amp.
The DC offset check is a very rudimentary way to ensure each op-amp is functioning as intended.
Do you have a high rez photo of the top side of the board handy?
It is a little easier to asses the soldering when we can actually see it and if the photo is clear enough we can zoom way in and ensure there are no solder bridges or some other problem?
(it is a royal pain to replace that op-amp with all of the other stuff in the way so let's try to make sure the problem is not something else before you go there)
 
May 7, 2009 at 6:33 PM Post #27 of 37
Quote:

Originally Posted by MisterX /img/forum/go_quote.gif
Yep.
The OPA690 is the ground channel op-amp.
The AD8397 is the left and right channel op-amp.
The DC offset check is a very rudimentary way to ensure each op-amp is functioning as intended.
Do you have a high rez photo of the top side of the board handy?
It is a little easier to asses the soldering when we can actually see it and if the photo is clear enough we can zoom way in and ensure there are no solder bridges or some other problem?
(it is a royal pain to replace that op-amp with all of the other stuff in the way so let's try to make sure the problem is not something else before you go there)


Yes, I can see that (and I have read that) that it will be a pain to remove.

Give me a few minutes and I'll get some photos up.
 
You must log in or register to reply here.

Users who are viewing this thread

Total: 4 (members: 0, guests: 4)
Back
Top