Plinius CD-101 repair

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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?

An externally hosted image should be here but it was not working when we last tested it.


An externally hosted image should be here but it was not working when we last tested it.

 
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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.
 
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.
 
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.
 
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.

An externally hosted image should be here but it was not working when we last tested it.
 
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.
 
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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.

An externally hosted image should be here but it was not working when we last tested it.

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.
 
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.

An externally hosted image should be here but it was not working when we last tested it.
 
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? I don't know what this servo function is for...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.

First: Do NOT mount a known good chip in the trouble location. You most likely would only destroy it too.

Second: Post a schematic of the circuit in question if you have one.

Third: I don't believe that an empty pad-17 should show any voltage. The PCM1704 features an internal servo amplifier that likely outputs the level of voltage you've measured on a good device. There should be an capacitor decoupling pad-17 to the -5V supply (see attached photo). If there's -5V volts on pad-17 without the chip mounted, it seems this decoupling capacitor is likely shorted and is blowing the servo amplifier. Replace this capacitor and re-check the voltage reading on pad-17. If it now shows no voltage, I think you've solved the problem and can solder a new PCM1704 in place.
 

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Airhead, I've thought about this a little more, and I shouldn't be surprised if that pad-17 capacitor is not faulty afterall. Without a DAC chip soldered in place, one end of the servo decoupling capacitor is tied to -5V but the other end is floating. Most electrolytic caps. exhibit some small amount of leakage current, probably enough to allow the -5V supply voltage to show through to the floating end at pad-17 when measured with a voltmeter. So, even after changing that cap., I suspect that you may find yourself still with the trouble.
 
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?
I am also interested for an answer.
Additional I want to know, from where I can order an optical pickup (laser unit) for the used ASUS cd rom transport
model "CD-S520B2" (CD-ROM drive).
Thank you for advices.

A test review is here:
https://webcache.googleusercontent....01/plinius-cd-101/+&cd=14&hl=de&ct=clnk&gl=de
and inside images are here:
https://www.head-case.org/forums/topic/4277-plinius-cd-101-internal-pics-specs/

For special questions about the PCM1704 ask there:
http://www.hoer-wege.de/dacup1704cmf.htm
hifiwerkstatt@ewe.net
 
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Airhead, I've thought about this a little more, and I shouldn't be surprised if that pad-17 capacitor is not faulty afterall. Without a DAC chip soldered in place, one end of the servo decoupling capacitor is tied to -5V but the other end is floating. Most electrolytic caps. exhibit some small amount of leakage current, probably enough to allow the -5V supply voltage to show through to the floating end at pad-17 when measured with a voltmeter. So, even after changing that cap., I suspect that you may find yourself still with the trouble.

You could gain some indication of what to expect, by measuring the voltage on empty pad-12 and pad-19. Both of those pads also feature an electrolytic cap. tied to -5V at one end and floating at at the other end. If both empty pads show -5V, like empty pad-17 does, all those caps are probably okay.
 
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You could gain some indication of what to expect, by measuring the voltage on empty pad-12 and pad-19. Both of those pads also feature an electrolytic cap. tied to -5V at one end and floating at at the other end. If both empty pads show -5V, like empty pad-17 does, all those caps are probably okay.

I replaced only C110 and C111 as I had them in hand (and respective caps on other channel) with fresh quality electrolytics. Voltage measurements are now:

Left channel, empty pads:
Pin 12: 0V
Pin 17: -5.0V
Pin 19: -5.0V


Right channel, chip on pads, voltages are fluctuating little:
Pin 12: -3.18V
Pin 17: -2.5V
Pin 19: -2.3V


I presume that servo amplifier is working? But I wonder why pin 12 on empty pad is 0V... Should I now put known good chip on the pads? I will immediately switch off it gets hot. Then I will know if the replacement PCM1704's from eBay are fake or not.
 
...I presume that servo amplifier is working?
My presumption as well.

But I wonder why pin 12 on empty pad is 0V... Should I now put known good chip on the pads? I will immediately switch off it gets hot. Then I will know if the replacement PCM1704's from eBay are fake or not.

I just noticed that the other end of the decoupling cap. associated with pad-12 is connected to ground, not to the -5V supply as are those other caps. So, it should read 0V, My error for suggesting to measure it.

Soldering a known good chip in place would answer the question of whether you've been sold defective or fake parts, but could result in the destruction of the known good device. I would first try replacing the known good PCM1704 in the working channel with one of the replacement PCM1704s you obtained online. If the working channel still works, then you know that the replacement devices are not the problem without having risked the destruction of the known good device.

Try not to heat the device pins and the PCB pads too much. You want to minimize the chance of thermal damage. Believe me, the more you fiddle around with soldering and desoldering the more likely you will suffer frustrating thermal damage. Be extra careful with the PCB pads, as they like to lift away from the PCB when heated too much. A damaged device is likely more easily replaced than is a damaged PCB.
 
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Soldering a known good chip in place would answer the question of whether you've been sold defective or fake parts, but could result in the destruction of the known good device. I would first try replacing the known good PCM1704 in the working channel with one of the replacement PCM1704s you obtained online. If the working channel still works, then you know that the replacement devices are not the problem without having risked the destruction of the known good device.

Try not to heat the device pins and the PCB pads too much. You want to minimize the chance of thermal damage. Believe me, the more you fiddle around with soldering and desoldering the more likely you will suffer frustrating thermal damage. Be extra careful with the PCB pads, as they like to lift away from the PCB when heated too much. A damaged device is likely more easily replaced than is a damaged PCB.

I will do that next week. We have professional hot air soldering rework station where I work: FINEPLACER micro rs - Hot Air SMD Rework Station
 
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