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Cambridge Audio CD3...

Discussion in 'd.i.y.' started by Dowser, May 8, 2017.

  1. Dowser

    Dowser Learning to bodge again..

    What is better than one TDA1541A DAC chip? Four, of course :)

    Many years ago I stupidly sold a CA C/P 75 pre/power combo before moving to Australia from England. I'd got it free after a huge burn up on one channel, many hours later of breaking away burnt PCB and rebuilding with hard wires, I had the first first real hifi I had heard (I had a Nad 3130 before that). I just assumed anything half decent above the quality of the Nad would sound similar...how wrong was I :)

    A few years after arriving in Oz, and becoming aware the combo was special, I have had my eyes open for a replcement combo from Stan Curtis, just to see if it lived up to the hype I personally placed on them. I also heard a two box Cambridge Audio CD player while in Oz (1995 to 1998), no idea of CD1 or CD2, but it sounded fantastic.

    Upon my return to CH in early 1999 I started a search for a CD3 (later one box player reputed with better reliability) - it finally came to fruition last week :) I bought a faulty one off a local auction site for far more than I should have (CHF 215) - it had a faulty display and only digital out worked.

    Checking rails, all was OK, putting a scope on output, all was OK - so I connected it up - worked for 5 mins and analogue out started breaking up and then disappeared. I stripped all connectors out to check components on board for anything obvious. Put it all back together and it has been playing nicely for over an hour now :)

    Initially pretty messy in the treble region, but has improved considerably since. The whole player (from 1998 or 1999 I guess) needs a proper service, loads of electrolytics and tants should be changed. Followed by a Flea and all the normal TDA mods...times four :)

    However, first I'd like to sort the display - it is numerical LED based and is flickering constantly, showing the correct track number every 3-8 seconds briefly before reverting to flickering. Pause and Repeat buttons also do not light their associated LED on front panel (pause works, have not tested repeat yet). Anyone come across similar? I will strip off the front panel later and replace all electrolytics, it must be isolated to the display/control circuitry somehow?

    Anyhoo - photos - upright boards hold the TDA1541As;
    [​IMG]

    The PCB at bottom right of this photo does not appear on any google image searches I perform - anyone seen it before? Somewhat dodgliy wired in, I wonder if it is aftermarket?
    [​IMG]

    Strange add-on PCB, and 4 lovely TDA1541A boards closer;
    [​IMG]

    With a decent CDM1 mech too :)
    [​IMG][/url]

    Thanks, Richard
     
  2. Mike P

    Mike P pfm Member

    Nice, I eagerly await a progress reports and full listening impressions!
     
  3. Dowser

    Dowser Learning to bodge again..

    I listened for some time last night, it got progressively better. it has something different to the normal 1541s I've heard - somehow fuller or bouncier.

    However, further analysis will have to wait until I have serviced it, and fixed display fault. Lots of caps to replace!

    Question on the axial smoothing caps - what are good replacements? I'll do a sympathetic restoration of this one I think, so axial so will stay axial.

    Thanks, Richard
     
  4. Darren

    Darren All Business

    Wonderful!! lusted after the CD1 for years. Failing that a CD2 or 3 like yours would have done very nicely. Lucky you. Hope it continues to please.
     
  5. martin clark

    martin clark pinko bodger

  6. James Evans

    James Evans Bedroom Bodger

    hificollective did have some 25v 4700uf axial caps but they're out of stock at the moment - may be worth getting in touch with them if that value works. They may be able to offer other sources as well.
     
  7. Dowser

    Dowser Learning to bodge again..

    I just spent CHF 103 on replacement caps from Farnell for the thing...it had better help :) 10k and 6k8 replacements for smoothers, plus a whole bunch of 47uf - all axial. CA used 16v parts on 15v rails! For the tants in PSU I have upped replacements to 25v.

    Seems the display unit itself is the fault after a bit of research, CA ran them a bit too hard apparently and most failed. I have a spare Philips CD150 in the cellar somewhere, hopefully same display unit, we'll see.

    That spare add-on board seems to be related to muting relays - manual I have only shows de-emphasis relay, my machine has 2 relays.
     
  8. Mike P

    Mike P pfm Member

    It sounds like you're sorted now but Farnell do have a reasonable selection of axial electrolytics in stock, particularly from Vishay and the Nichicon VX series.

    For the small radial electrolytics that do power supply decoupling of the +5v, -5v and -15v rails near the TDA1541 chips I used Rubycon ZLH 100uF 35v or 220uF 16v which are very good and will fit nicely. They're my favourite in this position when there's not enough room for a Silmic.

    My experience has been that parallel TDA1541 chips subjectively seems to give a more dynamic 'bigger' sound than a single chip but that a single chip can be smoother/more refined.

    Looking forward to the updates!
     
  9. Dowser

    Dowser Learning to bodge again..

    Thanks - yes, I chose Nichicon and Vishay for the main smoothers - not great I think, but then neither is what is in there from new :)

    I'm just going to recap it first, and then mod it depending on what I think. I'm a little concerned about that bigger sound thing that you mention, and that I preferred my Woodside overall to the un-serviced (and, of course, un-Flea'ed) CD3.

    I suspect this is getting to the age where it is worth more un-modified...however, it also seems rude not to throw a Flea into it, and a few of the other normal mods. I'm also interested to see whether there is a better option than the current op-amp output stages - need to investigate some more, but it seems the OP of each DAC is summed - if that is the case it should have 4 times the current of a single TDA chip, not sure whether that opens new opportunities yet :)

    Richard
     
  10. Mike P

    Mike P pfm Member

    I think you're right about it being worth more as a fully functional and serviced player than a modded one, should you ever decide to sell it. I'd be inclined to service it first so that you can evaluate it properly before doing anything irreversible.
     
  11. sam_cat

    sam_cat C'est Crounchifique!

    The Fleas are on their way, and I had a couple of spare Teddyreg PCBs that I have included too. :)
     
  12. mark121211

    mark121211 pfm Member

    If I remember correctly (and I sold my CD3 a long time ago) the CD3 DACs are not paralleled. The board that sits in front has a handful of logic IC's that shift the bits.
     
  13. Dowser

    Dowser Learning to bodge again..

    Thank you :)

    Yes, but the actual DAC L & R audio outputs are paralleled I think - via the op-amps as stock, and I know a Lampizized one is also done by joining all the outputs together before feeding it into the valve stage.

    I do some research closer to the time, first I refresh it and see how it performs stock. Why did you sell yours?

    Richard
     
  14. mark121211

    mark121211 pfm Member

    The L&R audio outputs from the 4 DAC's are mixed together.

    I sold mine mainly because I gave up on CD's. Streaming is so much better :)
     
  15. Dowser

    Dowser Learning to bodge again..

    Pulled the spare CDP out over the weekend - damn, it's a CD450 though and not 150 as I thought, which uses a slightly different display module (9 pins rather than 12);

    [​IMG]

    Sorry for poor focus. It does have a nice working CDM1 metal mech though, plus TDA1541 (non A) and SAA7220s sitting in IC holders...it goes back into storage :)

    Caps have arrived (and those boards - many thanks Sam!), so I'll set about recapping it.

    Richard
     
  16. Dowser

    Dowser Learning to bodge again..

  17. Dowser

    Dowser Learning to bodge again..

    I started the recap last night - only about a third of the way through. I forgot the Philips PCB strapped under the CDM1 mech - I had stock for all but a 1uF bipolar, which I have left in place. Can't remember which of these caps causes problems? The Philips axial 33uF had it's wrapper fall off when I removed it.

    Also, does anyone know in this PCB in the CDM1 mech has any electrolytics on it? I'm not familiar with the CDM1 really;
    [​IMG]

    This was the Philips 33uF position;
    [​IMG]

    And the old cap;
    [​IMG]

    New Vishay 47uF axial, versus original Samwha;
    [​IMG]

    Recapped servo control board (double sided and high quality...slow work!);
    [​IMG]

    I swapped all of these for Schottkys too;
    [​IMG]

    A pile of bits :) Need to finish the PSU and audio boards, then the display.
    [​IMG]

    Also, thinking about my display problem. The display on/off switch also does not work, so maybe my issue is not with the display unit itself, as switching off the display would be handled by the general control processor I assume. Will inspect it carefully while apart, and am recapping those boards too, so we'll see.

    Richard
     
  18. Dowser

    Dowser Learning to bodge again..

    Finished PSU and audio boards this evening, and put OP caps (5uF SiderealKap) on stand-offs to make swapping them easier. Photos;
    [​IMG]

    Just need to replace 3 caps on the 4x DAC boards now - 100uF are used for +/- 5v rails, and 10uF for -15v to the TDA. I have Panasonic FC 100uF 35v I could use in all positions - is OK? This is just a recap at this stage - additional decoupling will come later. Existing Samwha caps;
    [​IMG]

    And another question on the output caps - they're 5uF currently with, I think (it's a 6 band resitor used in this thing!), a 1k resistor to ground - what values can I safely change the OP cap with - I have wet tants at 10uF, Mullards and lots of others at 1uF (and maybe a couple of Mullards at 2.2uF) - will any any of these values be OK? Circuit and photos below:
    R11 & 12 are the resistors to ground after the caps;
    [​IMG]

    Circuit;
    [​IMG]

    6 band resistor - I think this is 1K?! :)
    [​IMG]

    Many thanks, Richard
     
  19. Mike P

    Mike P pfm Member

    My opinion is that sensibly, you won't be able to do any better than the original output coupling caps, they're ideal for the job.

    100uF FC's will be just dandy for all three voltage supplies on the TDA1541 chips, I've used up to 470uF FC's in the past with good results although I consider 100uF on the +5v, -5v and -15v supplies to be my 'standard' set up.
     
  20. Dowser

    Dowser Learning to bodge again..

    Thanks Mike, I start with the 100uf, they're a little bigger than stock but will still fit in original positions I think - forgot, I still need to recap display and control PCBs...ho-humm, about 4 hours invested so far :)
     

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