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Plinius CD-101 repair
Plinius CD-101 repair
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Old 22nd February 2017, 06:25 PM   #11
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by Airhead View Post
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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Old 22nd February 2017, 06:52 PM   #12
Ken Newton is offline Ken Newton  United States
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If you decide to replace the decoupling capcitor connected to pad-17, I suggest replacing all similar such capacitors around the chip while you're at it. If one capacitor is bad, any others like it may also be bad or marginal.
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Old 22nd February 2017, 07:21 PM   #13
Airhead is offline Airhead  Finland
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Thank you, Ken. I will check/replace the caps on both channels on pin 17 and measure voltages again tomorrow. Here's schematic:

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Old 23rd February 2017, 05:22 AM   #14
Ken Newton is offline Ken Newton  United States
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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.
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Old 23rd February 2017, 12:29 PM   #15
tiefbassuebertr is offline tiefbassuebertr  Germany
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Quote:
Originally Posted by Airhead View Post
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.c...&ct=clnk&gl=de
and inside images are here:
https://www.head-case.org/forums/top...al-pics-specs/

For special questions about the PCM1704 ask there:
http://www.hoer-wege.de/dacup1704cmf.htm
hifiwerkstatt@ewe.net

Last edited by tiefbassuebertr; 23rd February 2017 at 12:41 PM.
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Old 23rd February 2017, 01:56 PM   #16
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by Ken Newton View Post
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.

Last edited by Ken Newton; 23rd February 2017 at 01:58 PM.
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Old 23rd February 2017, 05:16 PM   #17
Airhead is offline Airhead  Finland
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Quote:
Originally Posted by Ken Newton View Post
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.
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Old 23rd February 2017, 05:17 PM   #18
Airhead is offline Airhead  Finland
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Hello,tiefbassuebert!

Thanks for the links. Do you have same player with same issue?

Last edited by Airhead; 23rd February 2017 at 05:26 PM.
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Old 23rd February 2017, 08:33 PM   #19
Ken Newton is offline Ken Newton  United States
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Quote:
Originally Posted by Airhead View Post
...I presume that servo amplifier is working?
My presumption as well.

Quote:
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.

Last edited by Ken Newton; 23rd February 2017 at 08:50 PM.
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Old 24th February 2017, 01:57 AM   #20
Airhead is offline Airhead  Finland
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Quote:
Originally Posted by Ken Newton View Post
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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