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Old 16th August 2011, 02:14 PM   #1
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Default Fried a Sony CXD9521Q?

Hello,

from time to time I fry something...

I was experimenting with various caps used in C378, C379 (CXD9521Q DAC digital decoupling, socketed) when, inserting a pair of Panasonic FM taken from my parts drawer, I've seen some little sparkles...

Damn, they were still charged! :O

Obiously the player was turned off but when I've powered it on no sound at all, completely mute...

I've taken some measurements and all seems fine, according to the Service Manual, except one on the DAC chip (see attached image).

It seems probable that the DAC is gone but if all other measures are correct how much hope there is it's the only one fried?

I'm correct saying that the wrong measured voltage is an indicator of the fault of the chip?

Thanks in advance to everyone that will try to help me troubleshoot

PS

In the attachment in green the caps that made sparkles, in blue the good measures, in red the wrong one
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File Type: jpg Sony.jpg (228.8 KB, 31 views)
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Last edited by ClaveFremen; 16th August 2011 at 02:19 PM.
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Old 19th August 2011, 11:45 PM   #2
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I would say the DAC IC is damaged if you saw sparks soldering in new caps and things are now silent The caps have 22 ohm resistors to the regulators, so most of the voltage spike probably went to the DAC IC. Did you do any other mods at the same time?
Checking pin voltages with a multimeter, it is hard to know if an IC is bad. An oscilloscope is a bit better, but there are thousands of transistors inside.
C379 is for DVDD (3.3V) and C378 for DVDD (5V?). Note the pin voltages are listed UNDER the pin. Pin 45 is 5V, not pin 46 which (Rch) should match pin 59 (Lch) at 2.5V and you getting 2.25V on pin 46 does not say much.

I would see if IC302 is running hot and use a scope to look at signals on the pins. The voltage reg IC312 is ok? Or just change the DAC IC.
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Old 20th August 2011, 02:18 AM   #3
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Hi prairiemystic,

first of all thanks for the answer

Quote:
Originally Posted by prairiemystic View Post
I would say the DAC IC is damaged if you saw sparks soldering in new caps and things are now silent The caps have 22 ohm resistors to the regulators, so most of the voltage spike probably went to the DAC IC. Did you do any other mods at the same time?
I do agree (and hope... )

No, I didn't other mods, I was testing several caps in those two positions thanks to sockets.

Quote:
Originally Posted by prairiemystic View Post
Checking pin voltages with a multimeter, it is hard to know if an IC is bad. An oscilloscope is a bit better, but there are thousands of transistors inside.
Sadly I don't have (yet) an oscilloscope...

Quote:
Originally Posted by prairiemystic View Post
C379 is for DVDD (3.3V) and C378 for DVDD (5V?). Note the pin voltages are listed UNDER the pin. Pin 45 is 5V, not pin 46 which (Rch) should match pin 59 (Lch) at 2.5V and you getting 2.25V on pin 46 does not say much.
I've measured voltage on decoupling caps (both the elco and the ceramic) so I'm pretty sure I've taken the right measure.

Quote:
Originally Posted by prairiemystic View Post
I would see if IC302 is running hot and use a scope to look at signals on the pins. The voltage reg IC312 is ok? Or just change the DAC IC.
Yes, IC312 seems good, all voltages are right.

I've searched the web for IC302 and it's not cheap and also I'm not sure abot the digital filter and I don't have yet an oscilloscope so I've brought it to a Sony Service Center two days ago...
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