Hi.
I am asking for a push in the right direction. My Naim CD1 has stopped sending out any audio (both channels) everything else work ok.
I have done some measurements:
No output ( 0 volt ) from the DAC (TDA1541A S1) pin 6 and 25
Power looks good. Pin 28 +5V, Pin 26 -5V and pin 15 -15V
Clock looks good. BCK 5.6MHz and SCK also 5.6MHz
LE/WS toggle every 16 clocks
There is data activity on pin 3
So I have replaced the DAC with a new one (Seller said it was new and unused so I payed big $$$$) but the replacement did not bring any audio out from the DAC.
So now I am a bit locked up. Can someone give me a hint on what to do next ?
Thanks in advance
/Jens
I am asking for a push in the right direction. My Naim CD1 has stopped sending out any audio (both channels) everything else work ok.
I have done some measurements:
No output ( 0 volt ) from the DAC (TDA1541A S1) pin 6 and 25
Power looks good. Pin 28 +5V, Pin 26 -5V and pin 15 -15V
Clock looks good. BCK 5.6MHz and SCK also 5.6MHz
LE/WS toggle every 16 clocks
There is data activity on pin 3
So I have replaced the DAC with a new one (Seller said it was new and unused so I payed big $$$$) but the replacement did not bring any audio out from the DAC.
So now I am a bit locked up. Can someone give me a hint on what to do next ?
Thanks in advance
/Jens
It's never the big chip 🙂
The data sheets shows this to be current output DAC. That means that the output on pins 6 and 25 isn't visible on a scope as it will be fed into a virtual earth amp (opamp). So you need to trace where pins 6 and 25 go (almost certainly to an inverting input pin on an opamp) and you need to scope the output pin of that opamp to see if any audio is present.
The data sheets shows this to be current output DAC. That means that the output on pins 6 and 25 isn't visible on a scope as it will be fed into a virtual earth amp (opamp). So you need to trace where pins 6 and 25 go (almost certainly to an inverting input pin on an opamp) and you need to scope the output pin of that opamp to see if any audio is present.
Boky:
Naim CD1 dosn't seem to have a S/PDIF output, so I don't think there is any analog mute !!! I may be wrong.
Mooly:
Good point. I have not seen that. The outputs are easy to trace. I will make some measurements and return.
Thanks to both of you.
/Jens
Naim CD1 dosn't seem to have a S/PDIF output, so I don't think there is any analog mute !!! I may be wrong.
Mooly:
Good point. I have not seen that. The outputs are easy to trace. I will make some measurements and return.
Thanks to both of you.
/Jens
I hope it wasn't an S1 double crown TDA1541A you removed? Might be wise reinstating it if you trace the problem to elsewhere.
I would suspect the Opamps... DAC output is practically zero if the I/V opamp works corectly - you should see voltage at the output pin of the first OpAmp.
Yes is was the S1 double crown.
Have done some more measurements:
Output from DAC goes to pin 2 of a opamp (OP42)
Power on OP42 looks ok (+17.6V and -17.6V)
No AC output on pin 6 (checked with scope when CD is playing/spinning) there is about 3-4V DC, same on both channels.
Output from first opamp goes via a Reed-relay to the next opamp (also a OP42), but the relay is not activated (open). Both relays (right and left channel) seems to be controlled by the DEEM signal, via a couple of transistors, from the SAA7310GP controller, the DEEM signal (pin 41) is always LOW
Any suggestions ?
/JJ
Have done some more measurements:
Output from DAC goes to pin 2 of a opamp (OP42)
Power on OP42 looks ok (+17.6V and -17.6V)
No AC output on pin 6 (checked with scope when CD is playing/spinning) there is about 3-4V DC, same on both channels.
Output from first opamp goes via a Reed-relay to the next opamp (also a OP42), but the relay is not activated (open). Both relays (right and left channel) seems to be controlled by the DEEM signal, via a couple of transistors, from the SAA7310GP controller, the DEEM signal (pin 41) is always LOW
Any suggestions ?
/JJ
Yes, that's exactly right. That first reed-relay is the CD deemphasis circuit, activated by a flag from SAA7220. It is normally -open, and only switches the extra RC components into circuit when HF demph is required. So your check shows it is probably ok.
This relay never breaks the continuity between the IV stage and next opamp.
Afterthought: check all the polystyrene caps have not gone 'short circuit'. A moments carelessness with the iron will melt them (perhaps when replacing the dac, and that will hold the audio signal to ground since there's an RC filter after each of the first two opamps in the output circuit (as part of 3rd order Sallen-Key filter design)
This relay never breaks the continuity between the IV stage and next opamp.
Afterthought: check all the polystyrene caps have not gone 'short circuit'. A moments carelessness with the iron will melt them (perhaps when replacing the dac, and that will hold the audio signal to ground since there's an RC filter after each of the first two opamps in the output circuit (as part of 3rd order Sallen-Key filter design)
Thanks Martin.
All poly-caps checked, no shorts.
No signal after first opamp, on both left and right channel.
The failure occured suddenly. One day the player was ok, and the next day it dosn't work, and has not worked since.
Is it possible to find a circuit diagram anywhere on the Internet ?
I really don't know what to do 🙁
/JJ
All poly-caps checked, no shorts.
No signal after first opamp, on both left and right channel.
The failure occured suddenly. One day the player was ok, and the next day it dosn't work, and has not worked since.
Is it possible to find a circuit diagram anywhere on the Internet ?
I really don't know what to do 🙁
/JJ
Pulled the TDA1541 out.
Injected a 1KHz 0.1Vpp signal at the DAC pin 6 and 25 on the PCB. That gave me a very nice 1KHz to be measured at the output connector
So the failure must be between the drive and the DAC...... I think
Any suggestions ? Things to try ?
/Jens
Injected a 1KHz 0.1Vpp signal at the DAC pin 6 and 25 on the PCB. That gave me a very nice 1KHz to be measured at the output connector
So the failure must be between the drive and the DAC...... I think
Any suggestions ? Things to try ?
/Jens
First step has to be a circuit and making a list of the chip set. Many Philips players will be very similar such as (perhaps 🙂) the CD630. What you are looking for are players that use the same chip set.
Philips CD630 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
List of players that use the TDA 1541,
List of players with 1541 [Archive] - pink fish media
I would begin by going round every pin on the TDA1541 (with CD playing) and check with a scope as well as DVM. Every pin, even if it's ground check it.
As a matter of course (and it almost certainly isn't this) I always check and confirm the RF (eye pattern) is of correct amplitude. Have had player that would read the TOC and spin up and the display updates but no audio due to low RF (low laser emission).
You have to cover all bases when faultfinding... don't assume a single thing is correct until measured and proved OK.
Philips CD630 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine
List of players that use the TDA 1541,
List of players with 1541 [Archive] - pink fish media
I would begin by going round every pin on the TDA1541 (with CD playing) and check with a scope as well as DVM. Every pin, even if it's ground check it.
As a matter of course (and it almost certainly isn't this) I always check and confirm the RF (eye pattern) is of correct amplitude. Have had player that would read the TOC and spin up and the display updates but no audio due to low RF (low laser emission).
You have to cover all bases when faultfinding... don't assume a single thing is correct until measured and proved OK.
Chipset is:
Controller: Motorola ZC99685
Decoder: Philips SAA7310GP with RAM MN4264P-15
Filter: Philips SAA7220P/B
DAC: Philips TDA1541A S1
Mooly:
Is the RF signal, you mention, and the HFI pin 32 on SAA7310GP the same ?
What amplitude is ok ?
Boky:
I don't have any ext. DAC Where do I find this S/PDIF signal ?
Thanks.
/JJ
Controller: Motorola ZC99685
Decoder: Philips SAA7310GP with RAM MN4264P-15
Filter: Philips SAA7220P/B
DAC: Philips TDA1541A S1
Mooly:
Is the RF signal, you mention, and the HFI pin 32 on SAA7310GP the same ?
What amplitude is ok ?
Boky:
I don't have any ext. DAC Where do I find this S/PDIF signal ?
Thanks.
/JJ
I have a +2 volt DC on pin 32 (HFI) of the SAA7310 decoder.
When playing a CD (Christmas songs ) there is a 1.2 Vpp AC signal
Is that ok ?
/JJ
When playing a CD (Christmas songs ) there is a 1.2 Vpp AC signal
Is that ok ?
/JJ
Once the RF has been processed and gone through a "data slicer" all you see is digital "hash". Scoping it can't tell you it is correct or not but the fact that the servos lock, the disc runs at the right speed and the display advances correctly mean that it almost certainly is.
It would help to see the full circuit of it all. RAM is notorious for playing up but usually gives rise to crackling as here,
http://www.diyaudio.com/forums/digital-source/171326-cd-player-distortion-laser.html
Can't say I've ever had it cause no audio... worth a measure around though by looking at all the data sheets and going round all the IC's
It would help to see the full circuit of it all. RAM is notorious for playing up but usually gives rise to crackling as here,
http://www.diyaudio.com/forums/digital-source/171326-cd-player-distortion-laser.html
Can't say I've ever had it cause no audio... worth a measure around though by looking at all the data sheets and going round all the IC's
check out also this thread:
http://www.diyaudio.com/forums/digi...d1-cd-1-cds-only-impaired-skip-operation.html
http://www.diyaudio.com/forums/digi...d1-cd-1-cds-only-impaired-skip-operation.html
On pins 3 & 4 of the 1541, with a scope & disc playing a music track, you should see a square wave of varying frequency. On pins 1 & 2, I believe, you should see a fixed frequency square wave, i.e., that you can get your scope to trigger onto & make nice, regular wave accross the screen. If these all seem ok, then one of the three supply lines must be amiss. You need +5v on pin 28, -5v on 26 & -15v on 15. If you don't have the right signals coming in, then you may have a bad signal processor chip, or a fault in the interconnecting lines in between.
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