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Plinius CD-101 repair
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Old 9th February 2017, 04:19 PM   #1
Airhead is offline Airhead  Finland
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Default Plinius CD-101 repair

I have two CD-101's from friends for repair and both have dead Burr-Brown's PCM 1704 DAC chips in left channel. Plinius tech recommended to replace PCM 1704 and I did so but new chip gets too hot to touch in few seconds after power is on. It was easy to replace as DAC circuit is on the separate PCB plugged on the motherboard. All voltages on test points are as they should. Any idea what causes that exessive heat? I fear that the new chips fries too if I keep the player on long time enough. Strange that both players have same fault, could this be common failure on CD-101?

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Last edited by Airhead; 14th February 2017 at 06:24 PM.
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Old 14th February 2017, 06:24 PM   #2
Airhead is offline Airhead  Finland
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Does anyone have idea about this?
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Old 21st February 2017, 03:22 AM   #3
Ken Newton is offline Ken Newton  United States
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This sounds a bit puzzling. If all supply voltages are correct, there may be a supply short to one of the DAC's non-supply pins. I suggest powering up the board without the DAC chip mounted and measure for a supply voltage on one of the pads that shouldn't be.

Another possibility is that you are soldering the chip in a reversed orientation, which may be destroying the chip as soon as power is applied. While that is probably unlikely, I have seen it done before. Double verify the correct orientation of the DAC chip's pin-1 location on the board.
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Old 21st February 2017, 05:54 PM   #4
Airhead is offline Airhead  Finland
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Originally Posted by Ken Newton View Post
This sounds a bit puzzling. If all supply voltages are correct, there may be a supply short to one of the DAC's non-supply pins. I suggest powering up the board without the DAC chip mounted and measure for a supply voltage on one of the pads that shouldn't be.

Another possibility is that you are soldering the chip in a reversed orientation, which may be destroying the chip as soon as power is applied. While that is probably unlikely, I have seen it done before. Double verify the correct orientation of the DAC chip's pin-1 location on the board.
Thank you for suggestions. I will desolder chip and measure voltages from pads. Chip should be correctly oriented, as on lower picture attached in first post, the chip is replaced with new one.
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Old 21st February 2017, 09:14 PM   #5
Ken Newton is offline Ken Newton  United States
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Also, be certain that you have the daughter board correctly oriented when connecting it in to the motherboard. If the DAC chips are becoming too hot to touch within seconds it seems to me that they are likely getting destroyed by an incorrect or improper voltage being applied to one or more pins.

The PCM1704 has been out of production for years, so legitimate stocks are shrinking. Were the replacement devices obtained from a reputable source? If not, it's possible you may have been scammed in to buying defective, or even fake, devices.
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Old 22nd February 2017, 02:25 PM   #6
Airhead is offline Airhead  Finland
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Originally Posted by Ken Newton View Post
Also, be certain that you have the daughter board correctly oriented when connecting it in to the motherboard. If the DAC chips are becoming too hot to touch within seconds it seems to me that they are likely getting destroyed by an incorrect or improper voltage being applied to one or more pins.

The PCM1704 has been out of production for years, so legitimate stocks are shrinking. Were the replacement devices obtained from a reputable source? If not, it's possible you may have been scammed in to buying defective, or even fake, devices.
They were bought from eBay, Hong Kong seller: 1P IC BURR-BROWN/BB SOP-20 PCM1704U PCM1704 | eBay

Please have look at the photo, above is orginal chip, below is replacement.

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Old 22nd February 2017, 03:58 PM   #7
Ken Newton is offline Ken Newton  United States
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Originally Posted by Airhead View Post
They were bought from eBay, Hong Kong seller: 1P IC BURR-BROWN/BB SOP-20 PCM1704U PCM1704 | eBay

Please have look at the photo, above is orginal chip, below is replacement.
I'm not familiar enough with PCM1704 device code marking to offer any opinion on whether genuine or fake. Sellers of fake devices are reasonably skilled at making them appear genuine via the code marking. Even should the markings indicate a genuine part, that doesn't verify whether or not these are failed devices being sold as good.

Also, I know absolutely nothing about the vendor you've purchased them from. Perhaps, someone else here has an relevant experience to offer. I do know that it appears genuine good PCM1704 stocks are fast dwindling.

Last edited by Ken Newton; 22nd February 2017 at 04:11 PM.
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Old 22nd February 2017, 04:34 PM   #8
basi is offline basi  Croatia
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Quote:
Originally Posted by Airhead View Post
They were bought from eBay, Hong Kong seller: 1P IC BURR-BROWN/BB SOP-20 PCM1704U PCM1704 | eBay

Please have look at the photo, above is orginal chip, below is replacement.

Click the image to open in full size.
Do you see letter J on the right side of the orginal chip.Well that is grade rank.They should be or letter J or K or the dots. J-grade is one white dot
K-grade is two white dot.

And now look the bottom chip.
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Old 22nd February 2017, 05:04 PM   #9
Airhead is offline Airhead  Finland
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Maybe chips should have been purchased from more reputable seller... Who knows, they may be fake.

I measured voltages in pads without chip in place and compared to working channel's respecting pins. All are same except one diffirence, pin 17 (Servo DC). Good channel have -2,23V and not working channel have -5,0V on pin 17. Maybe it's because chip is not in place? Idon't know what this servo function is for.
Datasheet with application schematic: PCM1704 pdf, PCM1704 description, PCM1704 datasheets, PCM1704 view ::: ALLDATASHEET :::

I have also option to remove known good PCM 1704 from other player and put it on the faulty channel into this player what I'm working on, as I have two CD-101's that have same fault, on same channel (strange). Hopefully I don't end with another fried chip.

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Old 22nd February 2017, 05:08 PM   #10
Airhead is offline Airhead  Finland
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Originally Posted by basi View Post
Do you see letter J on the right side of the orginal chip.Well that is grade rank.They should be or letter J or K or the dots. J-grade is one white dot
K-grade is two white dot.

And now look the bottom chip.
Yeah, I see that. But does it make much diffirence if pinout is same? It should work anyway? Noise or distortion may be little worse in new chip?
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