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Hi I have a problem with my multichannel Buffalo III dac. It has just stopped working!!! It was working fine, but now it is dead. There is light in the LEDs on the 4 regulator modules, but there is no light in the LOCK LED. I have measured the voltages at the regulators and I’m a little puzzled at the values. My setup is: Placid HD PSU MiniDSP miniShark (I2S communication) Buffalo DAC III AVCC Dual Shunt Regulator Module Trident 3.3V Shunt Regulator Module Trident 1.2V Shunt Regulator Module 10uF caps at the 16 outputs. (removed when I did the measurements below) Voltage measurements: Placid HD PSU: output voltage: 5,24V. CCS Current set at 503 mA VDD_XO Trident 3.3V Shunt Regulator: input 5.24 V, output 3.31V DVCC Trident 3.3V Shunt Regulator: input 5.24 V, output 2.12V VDD 1.2V Shunt Regulator Module: input 5.24 V, output 0.15V AVCC Dual Shunt Regulator Module: input 5.24V, output at even output side: 2.27 V, output at odd output side: 0,12V, DVCC: 2.12V I hope some one can help with this. Regards Mikkel sismik11 attached the following image(s):  BIII.jpg (251kb) downloaded 27 time(s).You cannot view/download attachments. Try to login or register.
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Hi again
I did some more measurements. This time I measured the 4 small regulators, while not attached to the DAC. I applied 5,1V to the regulators and got the following results:
VDD_XO Trident 3.3V Shunt Regulator: input 5.1 V, output 3.35V (output while on DAC: 3.31V )
DVCC Trident 3.3V Shunt Regulator: input 5.1 V, output 3.4V (output while on DAC: 2.12V)
VDD 1.2V Shunt Regulator Module: input 5.1 V, output 1.5V (output while on DAC: 0.15V)
AVCC Dual Shunt Regulator Module: input 5.1V, output at even output side: 3.8V (while on DAC: 2.27 V), output at odd output side: 3.66V (while on DAC: 0.12V).
Looking at these measurements, I would say that the regulators are working, but DAC is defect.
Is it possible to return the DAC board for service or a replacement?
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When you are powering the DAC with Placid, how much current are you shunting?
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Not likely sismik11, I don't think so.
Measure mV DC across TP_shunt and TP_out. There you have the shunt current. What does the meter says ?
You should read at least 50mV.
I guess you mix up the shunt current with the CCS current.
CCS current = the total current "going in" the supply
Shunt current = the current that stays in the supply (and end up heating the sinks), when the "consumer" (The DAC) has taken it's amount.
I don't think 500mA is enough.
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Thank you AVR300. You were right. I mixed op the Shunt current and CCS current
My CCS current is 500mA
My Shunt current is 17 mA
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Give it a little more juice.
Aim for 50-100mA shunt.
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Hi
I turned the current up, till I got a 90mV read out across resistor R2A. This should be 90mA shunt current. Correct?
Unfortunately it had no effekt on the board and the output voltages of the small regulator were the same as I measured before (see 1st post)
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Originally Posted by: sismik11  Hi
I turned the current up, till I got a 90mV read out across resistor R2A. This should be 90mA shunt current. Correct?
Correct!
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Well it has now been about a month since the last post, and I still have not found a solution.
Can I return the DAC for service?
What is the procedure if I want to return it?
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I have tried to get some support. But I my guess you are very busy because I still have a broken DAC board. I know that I probably don’t have any warranty, but I need to know if the board is wasted and that I have to look for a new solution, or if I can get it fixed somehow.
I'm getting a little desperate here not having any music from my stereo.
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Sorry to hear that. Sounds similar to my problem, only I don't know how I fried my board. It was inside the chassis and playing beautifully. My best guess is some kind of electro static chock.
Anyway, I decided to buy a new board, and put in my order yesterday.
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Unfortunately neither Brian nor Myself are currently equipped to do repair work - but you could do repairs yourself with a hot air rework station..
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