very intreasting problem~

[takashi]

dear all,

i am facing a probrem, very intreaseing!
i have make a pcb using dir1703 and pcm1738, when i finish, i hook up the power and listen. it is fine! but after 1-2 mins, the pcm1738 began to die... and then i replace another, it happen again.

finally i give up, and then i jet some cleaning solvent to it, it work again, but when the cleaning solvent dry, it did not work again...
and then i jet cleaning solvent again....

😕 😕 😕 😕

 

[cowanrg]

sounds to me like the ultimate audiophile amp! one listen and you have to buy a new one. 😉

 

[Dave]

If the PCM1738 is in an SSOP package you may want to double check the solder joints. Also be careful not to over heat the thing.

 

[raindog]

i agree with dave, it sounds like a soldering problem; i know it sounds like a lot of work but if you can't determine the faulty soldering joint(s) by view or by aplying gentle pressure on them you may have to do all the soldering all over again
good luck

 

[takashi]

i have tried adding presure, and solder many times, and i use DMM to check connection.
and the ICs are not hot, so it will not be overheat.
still confuse......

 

[Netlist]

Hi takashi
What happens to the power supply when the chip starts dying?
Do the voltages remain stable?

/Hugo

 

[jan.didden]

interesting

Sounds like an overtemp problem to me. Using the cleaning solvent also has the effect of cooling it. Did you check the supply voltages? Not using 5V where 3.3V is expected?

Jan Didden

 

[Konrad]

Check surrounding circuits for occilation. The solvent makes the circuit to "stabilice" and when drying it becoms unstabile.

 

[Dave]

Maybe a thermal cut out in a regulator.

 

[IanHarvey]

dear all,

i finish, i hook up the power and listen. it is fine! but after 1-2 mins, the pcm1738 began to die...

Can you describe 'began to die' in more detail?

The sound gradually disappeared? Did it just get quieter, did it become more distorted? When it had "died", what did you hear?

Does the problem clear itself if you leave it turned off for an hour, or is replacing the pcm1738 the only way to fix the problem?

If the problem clears after leaving it off for a bit, try leaving it in the freezer for 30 minutes, then retrying the test. If it lasts for longer before 'dying' you almost certainly have a heat-related problem, and getting a can of freezer spray is the next step...

Cheers
IH

 

[takashi]

when it began die, it 's sound level become small and then have sound , "sasasasa..."
but behind the noise , the music still playing
after i jet the clearning solvent, it work nornal suddenly!!!😱

and i have tried replace the IC a lot of time...

and i touch the ic, not hot! cooler than normal temp of op-amp

so i am still finding out the reason , very interesting

 

[IanHarvey]

when it began die, it 's sound level become small and then have sound , "sasasasa..."

and i touch the ic, not hot! cooler than normal temp of op-amp

Do you have an op-amp for buffering the DAC's output? Is this getting noticeably warmer than room temperature? If so, it may be oscillating - there may be many causes of this (poor or incorrect power supply decoupling, bad layout, or even the wrong choice of op-amp).

Do you have a circuit diagram for this DAC?

Cheers
IH

 

[tiroth]

You can always give everthing a good blast of cold-spray and see which parts melt off the frost first. It is a good bet that one of them is beyond its absolute maximum ratings.

It does sound like the problem is not in the DAC, but in a reg or opamp.