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Joined: 10/19/2012(UTC) Posts: 4  Location: Northamptonshire
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Hi there,
My elderly Buffalo II is not well. While adjusting the I/V stage Avcc/2 voltage feed somehow the Avcc input went low resistance to earth and the Avcc reg voltage was current limited and dropped to 0.9 volts on that left side. The left input without Avcc reg fitted measures at 26 ohms (measured on a 3v meter). The Avcc input on the Right side (also with regs removed) measures at circa 120K ohms. Unless there is something between the Avcc input and the ESS9018 other than L5 which measures OK, I suspect this means the Ess9018 left hand Avcc input is damaged and thus unrepairable. Without a circuit diagram further diagnosis is not possible so I wonder if you could tell me if this is repairable or if this Buffalo II is now toast.
BTW the right channel works without fault if its Avcc alone is fed 3.4 volts.
Grateful for any assistance
John
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There are nothing but decoupling caps in parallel with the AVCC outputs.
Those are pretty easy to trace with a DMM.
If none of them are shorted then it has to be the DAC chip itself. :(
It would be very strange for one of the caps to fail.
For the DAC, it could have been some ESD or perhaps a brief short or over-voltage? Its tough to say from here.
Very sorry for the bad luck.
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Rank: Member
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Joined: 10/19/2012(UTC) Posts: 4 Location: Northamptonshire
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Thanks Russ, I have already lifted each of the caps to confirm that none of them are responsible, and as you say, all that is left if the ESS9018 chip itself. Probably caused by electrostatic discharge from my Avcc /2 feed as you suggest. Are you able to supply replacement ESS9018's as I'm able to remove and reflow a new one in place - there's nothing wrong with the rest of the board AFAICT.
Grateful for your help
John
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Rank: Member
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Joined: 10/19/2012(UTC) Posts: 4 Location: Northamptonshire
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Just to conclude this thread with the news that I was able to source and fit a replacement ESS9108 chip myself within three days via the very helpful ESS agents in the UK, a company called Ismosys. They were a very customer focussed bunch. I haven't switched on yet but I' confident that any remaining fault will be down to my SMD soldering skills rather linited as they are. This was my first SMD soldering job and was not for the faint hearted, though not rocket science either. Thanks to Brian and Russ for their help. John Edited by user Friday, March 1, 2013 5:30:27 PM(UTC)
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Rank: Member
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Sorry to hear about your troubles John. I hope you managed to restore the DAC. The IvyIII and Placids you sold me are working away nicely in my dual-mono setup. 
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Rank: Member
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Joined: 10/19/2012(UTC) Posts: 4 Location: Northamptonshire
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Thanks Kes, glad to hear the Ivy and Placid are performing well. I'm powering it all up again tomorrow so fingers crossed. Anyone want a single channel ESS9018 DAC chip with short pins?
John
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