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Cambridge Audio CD3...

Hi Massimo,

Is it the current limiting resistor for the NSM4202A display module?

In my CD2 the current limiting resistors were 2R2 but it is a known problem that the CD2 runs the displays a bit too bright causing them to fail prematurely. Because of this when I rebuilt my CD2 I used 3R3 which is the value that Philips use in their own players.

If the original got too hot I'd be tempted to fit a 1/2 watt component and mount it raised above the board to aid airflow/cooling.
 
Sorry Massimo - i only have what was on hifiengine, so also no values. If you can trace it someone can probably suggest a replacement value - does the resistor feed the drawer motor or a switch? First should be to understand why the resistor blew.

Or post a picture of the resistor?
 
It feeds the open/close switch. Sometimes it works, sometimes not.. When I power on the cd player it work and opens the drawer. Most of the time it doesn't close it. If I Turn off the player and turn it on again, it will close. The switch seems to work, anyway. The resistor burnt when I forced the drawer
 
R25 is actually part of the drawer motor drive circuit, and protects the motor drive transistors from the negative rail...but there my knowledge runs out I'm afraid, and no idea what a replacement value should be. But I would also be checking Q8-Q11 to ensure none of them are short circuit as well.

The CD2 uses the same drawer motor drive circuit, and the resistor is listed as R47 on the main PCB in the CD2, but the limited Cambridge Audio schematics and board layouts don't help unless I have a CD2 in front of me...and I don't I'm afraid.

I'd be looking for a Philips machine that uses the same version CDM laser and drawer mechanism, and then finding the service manual for that...there the resistors value will be listed on the schematic :)

Good luck!
 
Dowser said:
Tracing it all out (with help from the basic manual on HiFi Engine), the WS, DA and CL all seem to be there from the 7220. They go to that shift register PCB in front of the DAC boards. CL goes to shift register and all 4 DAC boards in a daisy chain. The WS and DA lines go unmodified to the first DAC board, but for the other 3 DAC boards they go to a SN74LS166N chip, and the output of that to the DAC boards.

The original WS and DA signals are much higher amplitude than the outputs from the shift registers (3.5v vs 2v pk-pk), and do not look remotely similar to me. However, they were all the same except one - the DA output for DAC PCB 4, which was 1v pk-pk and a complete mess.
[...]

I could probably swap the register chips around assuming it is only one logic gate that is faulty, and each DAC uses a different output. But the chips are only a £1 each, so I am going to order 6 new ones.

Some more photos
Shift Register PCB (after redoing solder joints);
34652863491_bd97acfbfb_c.jpg

33976265163_6587a2eeee_c.jpg
Click to expand...
Looks like a re-clocker. It's not in the crude HFE schematic.
You may be able to improve on the performance by replacing the 74LS166 with rare 74S166 (not LS).
 
Just to clarify: the outputs of the DACs are interleaved (hence the 16X oversampling, versus the usual 4X). Since they are current output they can be summed. The reason Stan did 16X was to use minimal filtering on the outputs.

The CD3 was a tidied up version of the CD2. Allegedly and inexplicably it didn’t sound as good as the CD2.
 
S-Man said:
Just to clarify: the outputs of the DACs are interleaved (hence the 16X oversampling, versus the usual 4X). Since they are current output they can be summed. The reason Stan did 16X was to use minimal filtering on the outputs.
Click to expand...
Was the CD3 really a 16x over-sampler? The CD2 has an addit. vertical board (green) full of eight 74 logic ICs. I assume this is 16 x board ??? The CD3 doesn't seem to have a similar board.
Below: CD2 from https://pinkfishmedia.net/forum/threads/any-cambridge-audio-cd2-owners-here.220115/
44189244285_26619d1144_c.jpg
 
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13mh13 said:
Was the CD3 really a 16x over-sampler? The CD2 has an addit. vertical board (green) full of eight 74 logic ICs. I assume this is 16 x board ??? The CD3 doesn't seem to have a similar board.
Click to expand...
Looking further into the 16x oversampling issue....
Hmmm ... both the CD2 and CD3 had the "16 x 16" label on the front. I think CD2 was from 1988 and CD3 from 1989. Yes?

S-Man said:
Just to clarify: the outputs of the DACs are interleaved (hence the 16X oversampling, versus the usual 4X). Since they are current output they can be summed. The reason Stan did 16X was to use minimal filtering on the outputs.
Click to expand...
I'm not buyin' it. What I see in the internal photos of both these units -- CD2 and CD3 --as well as that very crude and incomplete hand-drawn schematic (possibly by a service tech by laborious re-tracing) -- just does not "add up" to the 16x OS claim. At this time, the best that best that Japanese could do was 8x (using NPC filters) -- and those were far better researched.
And in the CD3, that vertical 74ls logic board off the motherboard disappeared but CA still called it 16 x 16.
Methinks the four tda1541 dacs are arranged as follows:
LEFT CH: two parallel stacked tda1541
RIGHT CH: two parallel stacked tda1541
I will stand corrected if one can prove the 16x claim.

REFS:

Cambridge Audio DAC3 & CD3M - 4x Philips TDA1541 - CDM1mkII - DutchAudioClassics.nl

DutchAudioClassics.nl - Cambridge Audio DAC3 & CD3M - 4x Philips TDA1541 - Philips CDM1mkII
dutchaudioclassics.nl dutchaudioclassics.nl

Cambridge Audio CD2 - 4x Philips TDA1541 - DutchAudioClassics.nl

DutchAudioClassics.nl - Cambridge Audio CD2 4x Philips TDA1541 review
dutchaudioclassics.nl dutchaudioclassics.nl
 
You could be right, I suppose the only way to know is to get inside one with a ‘scope and look at the clock timing for the DACs.

I don’t have one anymore.
 
The 1985 datasheet for the tda1541 notes max os rate is 4x.
The 1990 datasheet for the tda1541a notes max os rate is 8x.
I believe the CD2 was launched in 1988 when only the 1541 (non-a) was avail.
Maybe CD3 (1989??) also was (non-a) .
It's possible that DAC3, with "16x16" used tda1541a's.
If CA was to come out and claim, say, 16x -level "mathematical" performance -- similar to how D/A of early Philips 14-bit (with 4x) could achieve SINAD 16-bit ... well, this would be somewhat acceptable.
Multiple, parallel dacs (and with separate L/R dacs to boot) is good. As is 74-logic re-clocking .
While they were at it, CA should've invested in, say, discrete I/V or output state (and not op-amp based).
I see CA later switched their marketing language to something more ... ahem ... legal-friendly:
"DACMagic".
In any case, that front labeling is just plain UGLY ...
Cambridge-Audio-CD2-013.jpg
 
13mh13 said:
Looking further into the 16x oversampling issue....
Hmmm ... both the CD2 and CD3 had the "16 x 16" label on the front. I think CD2 was from 1988 and CD3 from 1989. Yes?


I'm not buyin' it. What I see in the internal photos of both these units -- CD2 and CD3 --as well as that very crude and incomplete hand-drawn schematic (possibly by a service tech by laborious re-tracing) -- just does not "add up" to the 16x OS claim. At this time, the best that best that Japanese could do was 8x (using NPC filters) -- and those were far better researched.
And in the CD3, that vertical 74ls logic board off the motherboard disappeared but CA still called it 16 x 16.
Methinks the four tda1541 dacs are arranged as follows:
LEFT CH: two parallel stacked tda1541
RIGHT CH: two parallel stacked tda1541
I will stand corrected if one can prove the 16x claim.

REFS:

Cambridge Audio DAC3 & CD3M - 4x Philips TDA1541 - CDM1mkII - DutchAudioClassics.nl

DutchAudioClassics.nl - Cambridge Audio DAC3 & CD3M - 4x Philips TDA1541 - Philips CDM1mkII
dutchaudioclassics.nl dutchaudioclassics.nl

Cambridge Audio CD2 - 4x Philips TDA1541 - DutchAudioClassics.nl

DutchAudioClassics.nl - Cambridge Audio CD2 4x Philips TDA1541 review
dutchaudioclassics.nl dutchaudioclassics.nl
Click to expand...
If you look at pictures of mine earlier in thread, you’ll see the logic board is there in CD3 too (in front of 4 DAC boards) - a faulty gate in one of the 74x chips was causing my issue.
 
I very nearly bought a CD3 back in 1989/1990, I thought it had the edge over the other CD players I tried. The demo machine struggled to load and play discs reliably probably because they chose to fit it with a sagging acrylic lid so that you could see the insides, which interfered with the mechanism.

Suitably impressed I bought something else but a family member did buy one and lovingly cared for it over many years of service despite it steadily failing along the way, the display and buttons being the main issues quite early on. It’s owner loving it for its charm calling it character :0)

I have Sony CDP esd model from that period and an earlier Philips CDP from 1985/86, both use the Philips TDA chips and both still work, although I did recap the Philips machine, the Galvo drive pcb seemed particularly hard on capacitors with the damper resistor/capacitor visibly under stress.

Thank you for persevering with your CDE, it has been interesting to see your remedial works,. It would be good to see a schematic.

I also hope that your work to revive the Naim players works out, it seems many give up on these which seems such a shame.
 
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