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Drofo  
#1 Posted : Sunday, December 18, 2011 9:27:18 AM(UTC)
Drofo

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Hi,
After months of satisfying sound from my DAC, I returned home to find no sound output.
The DAC has been generally powered at all times with no problem.
Case is well ventilated so no heat issues.
Both mute and lock lights were illuminated at all times.
When viewed, all tridents were lit and and the LED's on the dac were illuminated.

The voltages were fine and within range.
The LED on the MUX receiver was not illuminated, but would briefly flash on power up or down.
Bypassing the MUX receiver directly into the DAC yielded no change.

Any suggestions on the next step would be appreciated.

Regards,

Drofo

Edited by user Monday, December 19, 2011 10:15:54 AM(UTC)  | Reason: Not specified

Drofo  
#2 Posted : Tuesday, January 10, 2012 12:51:14 PM(UTC)
Drofo

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Hello all,
I posted this later last year.
Despite numerous views, so far no one has suggested where to start with this.
I am still wishing that anyone who might have some knowledge on troubleshooting this problem might be able /willing to get me started.
I have emailed both Brian and Russ privately, but so far have received no response.

I rally would like to get this working again, but as my knowledge is limited, am concerned about doing anything that may make the sit worse.
Failing this would anyone be interested in buying the working parts?

Thanks,
Drofo.
glt  
#3 Posted : Tuesday, January 10, 2012 1:20:50 PM(UTC)
glt

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Voltages on the AVCC board ok?
Lock LED is on when music is playing?
Russ White  
#4 Posted : Tuesday, January 10, 2012 1:56:41 PM(UTC)
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It sounds as if one possibility (of many) is that one or more of the digital inputs may be damaged (ESD possibly?) Try using SPDIF directly into the SPDIF terminal with the comparator switch on.

Edited by user Tuesday, January 10, 2012 4:43:57 PM(UTC)  | Reason: Not specified

alazira  
#5 Posted : Tuesday, January 10, 2012 3:46:29 PM(UTC)
alazira

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Drofo wrote:

Both mute and lock lights were illuminated at all times.


So are you saying the these lights are on at the same time?
Brian Donegan  
#6 Posted : Tuesday, January 10, 2012 3:53:30 PM(UTC)
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It sounds like a problem with your source.

If the MUX Lock led is not lighting, then it is not getting a lock.

If the Buffalo has both Lock and Mute lit, it indicates it is receiving an all-zero S/PDIF signal. If you disconnect the S/PDIF from the Buffalo and power it up (MUX also not conencted), you shoudl see Mute led only. Then attach the SPDIF while it is powered up, and you should see the Lock led light as well.

What source are you using?
Drofo  
#7 Posted : Wednesday, January 11, 2012 2:34:52 PM(UTC)
Drofo

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First, thank you glt, Russ, alazira and Brian for the help and suggestions. This is an excellent DAC, and without it I miss the attack and liveliness in music.

The DAC has worked flawlessly since build until this incident. When I moved in September,the DAC became prone to ground bounce at this location, but not at previous location. This while troublesome, did not affect the operation.
Placed X cap across AC inputs, but did not change.

Digital and low level sources are fed from a filtered AC supply.
Normally digital sources are powered on at all times.
Only on this one occasion returned home to find no signal from DAC.

To answer the questions:
Voltages:

Placid 1 feeds MUX = 5.5v
Placid 2 Feeds Buffalo II + 5.5v
Placid BP to Legato = - 14.5 , +14.6

Current measured at Placid BP .056, .058
AVCC voltages ok.

When initially powered on, both lock and mute light illuminated.
2 sources are in use:
First is a Squeezebox, the second is a CD player. Both work properly through SPDIF into an older DAC, so they are not suspect.

On Buffalo II selecting either output with MUX, the lock and mute lights remain illuminated.
Bypassing MUX directly into SPDIF on Buffalo II does not have any effect.
Also disconnecting and reconnecting SPDIF, does not change MUTE/ LOCK light.

DAC remains silent through all above changes.
DAC was prone to ground bounce at this location, but not at previous location. Placed X cap across AC inputs, but did not change.
Unsure if that would cause any damage.

Thank you.

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Russ White  
#8 Posted : Wednesday, January 11, 2012 4:10:26 PM(UTC)
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Have you check the trident voltages? Double check solder joints around the tridents.
Drofo  
#9 Posted : Thursday, January 12, 2012 1:29:05 PM(UTC)
Drofo

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Hi Russ,

You have it right. he 3.3v Tridents both read correctly at 3.29 and 3.31
The 1.2V trident reads nothing at all.
The solder joints are all good.

Funny I thought they would be fine since they were illuminated.
Is there anything else that I should look for, before I replace the trident?
Is there anything that would cause this or is it just freak failure?

Thanks much for your help.

Drofo.

alazira  
#10 Posted : Thursday, January 12, 2012 1:57:00 PM(UTC)
alazira

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Drofo wrote:
Hi Russ,

You have it right. he 3.3v Tridents both read correctly at 3.29 and 3.31
The 1.2V trident reads nothing at all.
The solder joints are all good.

Funny I thought they would be fine since they were illuminated.
Is there anything else that I should look for, before I replace the trident?
Is there anything that would cause this or is it just freak failure?

Thanks much for your help.

Drofo.



This exact same thing happened to me. A 1.2V trident failed but I did not know because the LED's remained lit (cost me hours of troubleshooting as I assumed they were functioning). These run at a much higher current than the 3.3V so perhaps they are more prone to failure?
Russ White  
#11 Posted : Thursday, January 12, 2012 2:51:42 PM(UTC)
Russ White

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They run hottest and are the most prone to fail if supplied with too much voltage. You might try replacing the transistors (usually Q2 is culprit). Also just be sure that R4 is well soldered.

Occasionally the op-amp will fail, but this is more rare.
Drofo  
#12 Posted : Saturday, January 14, 2012 6:28:16 PM(UTC)
Drofo

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Thanks Russ,

I will replace Q2 this week and see how it goes.
As is it, I have already ordered a replacement 1.2v Trident, just in case.

Regards,

Drofo
Drofo  
#13 Posted : Saturday, March 31, 2012 7:08:24 AM(UTC)
Drofo

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Problem solved.
Turns out the 1.2v Trident was the culprit. When it was replaced everything returned to normal.

Thanks for all the assistance.

Regards.
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