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Hello,
I just FINALLY finished my Sympatico and was doing some testing before inserting it into the rest of my system. When checking for DC at the speaker terminals I found the left channel had 2uV but the right channel had 14.5V! I grounded the inputs and the left channel rose to 4mV but the right was even higher at 29.7V!
I bought bare boards and soldered everything myself so I double and triple checked for any solder bridges or bad joints. I didn't find anything that worried me but I did reflow the connections for the LM4780. Checked the DC again and got the same results. That high of a DC voltage leads me to believe that something is very wrong. I left the amp powered on for 3 or 4 minutes and nothing on the right channel amp was even warm.
Has anyone seen something like this or can somebody point me in the direction that I need to look?
Thanks in advance,
Ty
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Check the feedback loop from the LM4780 to the OPA1632. Make sure those comps are fully soldered and correct.
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Thanks Brian, I'll take a look
I'm guessing that you mean caps not comps though, correct?
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I ended up just replacing C1 and C2. Checked again and still at 14.5V DC at the output. Is it possible that my LM4780 is bad?
Thanks
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Rank: Administration
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Originally Posted by: TKO956  Thanks Brian, I'll take a look
I'm guessing that you mean caps not comps though, correct? I meant comp(onents). Resistors and capacitors. It is possible that the LM chip is bad, but just as likely there is another bad component. Can you post a picture?
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I ended up reflowing everything on the board and the DC is now jumping around between 7V and 10V. It does look like something just has a bad solder joint. I'll hit everything again later today when I have time. I did check all of the resistor values and they are correct. I attached the picture. Please let me know if you see anything obvious other than the solder bridge between R1 and R11. I figured that it wasn't that big of a deal since they are attached by a trace anyway. Thanks.  amp1.jpg (106kb) downloaded 8 time(s).Edited by user Thursday, May 2, 2019 6:03:34 PM(UTC)
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Rank: Member
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Reflowed all the components again and the DC on the right channel is now 9mV. Thanks for the help, Brian. Edited by moderator Monday, May 6, 2019 5:14:36 PM(UTC)
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