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Buffalo Problem. Fine on bench, however problem with SPDIF causing volt fluctuations
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Hello, With no SPDIF connection, everything is fine.
When I plug in the SPDIF from the CD player, I get a voltage fluctuation every second which causes the dimming of D1 on the regulator and a voltage from the reg sags from 5.4volts to 4.6volts, up and down every second. The D1 on the voltage regulator on the plug in module of the Buffalo goes from 3.3v to 2.8 volts, up and down very second. The output from my IV converter gives +2 v ac on these spikes.
Any Ideas?
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Are you using placid? If so it sounds like your CCS current is not high enough. Edited by user Monday, October 10, 2011 10:23:32 AM(UTC)
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Rank: Member
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Russ,
Yes I am using a Placid. I checked that the shunted current measured 0.06v or 60ma across the test resistor after the placid was hooked to the Buffalo. I will go back through the CCS and double check the total current. Originally the Placid voltages came out like expected in the initial test setup with I put it together.
It is like trying to start a car with a weak battery.
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OK, The current from the Placid was too low. Adjusted, that fixed the power issue. Also, I had forgotten to take out the standard controller 8 pin chip when I hooked up the Volumite. That fixed the pumping. HOWEVER, I now notice that the right channel out of the Buffalo is silent.
The left channel is fine and sounds great. When I hook up both of my IV converters to the Left channel I get glorious two speaker mono.In testing, I unhooked the Volumite and used the standard on-board controller chip and the right channel still gone. And using the Volumite, the right channel is gone. Don't know if this is related. I get a great lock immediately, however the Mute LED never lights. The very first time I powered it up, the Mute lit, but nothing since then. All other LEDs light nice and steady. I get 3.3 volts on both of the tiny little "out" pins of the included plug in voltage reg (AVCC) that plugs into the Buffalo. When I put my meter on the right channel +/- out the readings are nothing compared to the L channel. Any more Ideas? Thanks Chris O Edited by user Monday, October 10, 2011 8:02:51 PM(UTC)
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Rank: Administration
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Joined: 10/24/2006(UTC)
Posts: 3,979
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It might be time to post some pictures. Sounds like something is loose. Maybe the connection between the DAC and the output stage?
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Most of the power supply is in a different chassis.
I have the Placid, Buffalo and two of Welborne Labs "Cato" I/V converters.
I don't think the problem is related to the Connections or the I/V converters because they both work fine hooked up to the left channel.
I am using both the + and the - out into the I/V converter and when I measure the values of those points on the Buffalo itself, both are the same and non-existent voltage readings.
I am an experienced builder.
Do you have a photo-up load feature or does the image need to be hosted first?
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Rank: Administration
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Click the attach button on the top right on your existing post.
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Rank: Administration
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ChrisO wrote:both are the same and non-existent voltage readings. What? Can you be more specific?
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When I have the unit hooked up being fed with S/PDIF signal, I measured the AC voltage between + and ground as well as - and ground on both of the Buffalo II's channel outputs. The left side showed AC voltage (signal output) the right side did not.
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Rank: Administration
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This is with out without the output stage connected? Measure it with no output stage. Make sure the AVCC module is making good contact on both sides.
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Hey Russ, Today at lunch I did the measurements with no I/V stage connected. With S/PDIF hooked up and locked the peak hold AC measurements were Left Channel (+) 0.5 VAC ( -) 0.5 VAC Right Channel (+) 0.0 VAC ( -) 0.0 VAC I reseated the AVCC. Is there a point on the Buffalo board were I can verify the 3.3v from the AVCC is getting to where it needs to be? ChrisO attached the following image(s):  Buffalo II.jpg (39kb) downloaded 124 time(s).You cannot view/download attachments. Try to login or register.
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Rank: Administration
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I would check(carefully) across C6 and/or C7.
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What are you using for firmware? I know you mentioned volumite, but is that still what you are using? Is the result any different with the on-board firmware? Edited by user Tuesday, October 11, 2011 12:12:46 PM(UTC)
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The first test I did was with the on-board firmware in place and no Volumite. I then took out the on-board firmware chip and hooked up the Volumite; the Volumite changes the volume like it should. In both cases, the right channel is silent. I will (carefully) check the voltage on the caps you mentioned. Edited by user Tuesday, October 11, 2011 12:47:57 PM(UTC)
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Rank: Administration
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Excellent just double checking.
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Russ, Thanks so much for taking the time to go through this with me. I measured the AVCC outs and both are just over 3.5volts and the same. I managed to carefully get a probe back to C7 and the voltage was 0.87 volts. Thanks, Chris O ChrisO attached the following image(s): IMG_3941.JPG (136kb) downloaded 88 time(s).You cannot view/download attachments. Try to login or register.
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
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Ok that indicates that there are at least the following possibilities: 1) a bad connection at the right AVCC output. (especially if the AVCC output is not sagging at all (not .87V)) 2) a short or damaged analog section of the DAC. (but only of the right AVCC output is also at .87V. Double check the solder joints and the ferrite under the AVCC module. Edited by user Tuesday, October 11, 2011 7:24:43 PM(UTC)
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YOU GOT IT! THANKS RUSS. :d/
On the bottom side, the four solder joints of the AVCC header all looked good, but one was obviously not as good as the others. Ahh headers. The 3.5 volts became 0.87 volts going to L4. A quick re-hit and all is well!
It has been so long since I have had a bad solder joint I grew overconfident. Thanks for helping me.
Chris O
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Rank: Administration
Groups: Administration, Customer
Joined: 10/24/2006(UTC)
Posts: 3,979
Location: Nashville, TN
Thanks: 25 times
Was thanked: 89 time(s) in 83 post(s)
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Very glad to help. Enjoy your DAC. :)
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Buffalo Problem. Fine on bench, however problem with SPDIF causing volt fluctuations
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