cdm4 mechanical problem - disc rubs, not spinning freely (solved, mods report)
Hi,
I did a thorough search on diyaudio but couldn't find anything concrete, so I'm asking for a little help or suggestions:
Just got a well looking Grundig CD3000 (cdm4 with tda1543, planning some nice mods here when I get it working), which doesn't read discs for a low price. Tested it and turns out that the laser appears to be fine, fortunately, but it rather seems to have a mechanical problem: the disc starts to spin but seems to rub against the base of the transport or the platter, I'm not sure, so it gives up with ERR. I decided to test further by inserting a piece of paper underneath the cd onto the disc platter - now, disc would rub less and start to spin up to right speed, making less rubbing noise, but still not reading. I figured the focus distance would not be perfect due to the paper, so I slightly pressed on top of the clamp and now the player was able to read TOC and started to read a track with heavy skipping. Still some rubbing sound, which would explain the skipping.
So, does anyone have an idea what might be the problem? If it was a CDM1 I'd say that the disc platter had lowered on the shaft due to wear, but I don't think this can happen to cdm4, also the paper test seems to prove the opposite, as it only starts reading when pressed down (so it can't be lower than original, as I haven't touched any trimpots).
Could it be damaged or worn clamp? I've heard about some bearing but I can't seem to find it. Could the transport base not get low enough when loading the disc and be rubbing against the cd? a very well working tray loading mechanism (often these infamous gear breaks) speaks against this, but I don't know.
I have two other working cdm4 based players here, so I might start to compare them bit by bit to the defective cdm4 and try to find out what's going on, but I though maybe this is a common problem and someone could give me some hints, sparing me some time.
Thanks in advance.
P.S.: I've repaired a couple of CDM2 transports so I've got general knowledge about repairing philips swing arm mechanism, but didn't repair any cdm4 yet.
Hi,
I did a thorough search on diyaudio but couldn't find anything concrete, so I'm asking for a little help or suggestions:
Just got a well looking Grundig CD3000 (cdm4 with tda1543, planning some nice mods here when I get it working), which doesn't read discs for a low price. Tested it and turns out that the laser appears to be fine, fortunately, but it rather seems to have a mechanical problem: the disc starts to spin but seems to rub against the base of the transport or the platter, I'm not sure, so it gives up with ERR. I decided to test further by inserting a piece of paper underneath the cd onto the disc platter - now, disc would rub less and start to spin up to right speed, making less rubbing noise, but still not reading. I figured the focus distance would not be perfect due to the paper, so I slightly pressed on top of the clamp and now the player was able to read TOC and started to read a track with heavy skipping. Still some rubbing sound, which would explain the skipping.
So, does anyone have an idea what might be the problem? If it was a CDM1 I'd say that the disc platter had lowered on the shaft due to wear, but I don't think this can happen to cdm4, also the paper test seems to prove the opposite, as it only starts reading when pressed down (so it can't be lower than original, as I haven't touched any trimpots).
Could it be damaged or worn clamp? I've heard about some bearing but I can't seem to find it. Could the transport base not get low enough when loading the disc and be rubbing against the cd? a very well working tray loading mechanism (often these infamous gear breaks) speaks against this, but I don't know.
I have two other working cdm4 based players here, so I might start to compare them bit by bit to the defective cdm4 and try to find out what's going on, but I though maybe this is a common problem and someone could give me some hints, sparing me some time.
Thanks in advance.
P.S.: I've repaired a couple of CDM2 transports so I've got general knowledge about repairing philips swing arm mechanism, but didn't repair any cdm4 yet.
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Poynton: thanks for the information, will be helpful, I'm sure. And yes, I'll definitely swap mechanisms if I can't find out what's happening.
freebee: yes, I'm sure, the CD is touching the deck, it's pretty obvious, not the laser/focus. The laser seems to be fine, as far as I can test (with the paper trick I managed to get it to read TOC and play with failures, but that's because the disc was still rubbing a little and distance was changed due to the paper sheet, so I assume laser is fine).
In the meanwhile I found this thread (CDM4/19 skips), I'll check if that might be the problem.
freebee: yes, I'm sure, the CD is touching the deck, it's pretty obvious, not the laser/focus. The laser seems to be fine, as far as I can test (with the paper trick I managed to get it to read TOC and play with failures, but that's because the disc was still rubbing a little and distance was changed due to the paper sheet, so I assume laser is fine).
In the meanwhile I found this thread (CDM4/19 skips), I'll check if that might be the problem.
Well, been doing some tests and some progress. This is what I found out so far:
- it's not the clamp ball bearing problem (exchanged the clamp with other players I have, also tried playing CD without clamp fixed with blue tac).
- gap between platter and deck is more or less identical to the other cdm-4s which I got and are working is about 1 mmm as Poynton said), still, when the tray is inserted, the disc is clearly scraping against it, you can even feel it when turning the clamped cd with your hands. This seems to be a problem related to the tray, I will compare with one of the cdm4s, which is a cheapo Philips which I got only as a donor for the laser mechanism to have a spare laser for my Marantz CD40, so I could eventually take its tray and adapt it to the Grundig, if the tray turns out to be damaged. But that's not all for now, more follows:
- with the tray taken out, cd is not touching the deck and spins freely, player immediately reads TOC (every time) (I fixed the CD with bostix, blue tack, whatever you call it).
BUT:
- player will read first track almost fine (maybe a couple of skips later), will jump to all tracks (pressed good condition CD), but from second track on it will skip more and more, as you approach further tracks, clearly you hear the laser whining, even on first track, I know that's clear indication that something is wrong.
- another thing I noted, I'm not sure it's normal: the swing arm doesn't rest about its middle position, it rests close to the platter (so at TOC position), is that normal? Both other cdm4s have the swing arm somewhere in the middle (one close to centre, the other perfectly in the middle of its travel), could that mean that there's a problem with the swing arm? But then I've google cdm-4 images and some do rest close to centre position. Swing arm moves freely.
- Now, as I have another player which is only donor for working cdm-4, I took that working unit out and installed the cdm-4 from the Grundig. It passes all service positions, radial swing arm moves well, focus is found immediately, laser seems to be fine (compared image through digital camera, red dot seems similar to red dot in other known good cdm-4's), but focus actions makes "squeak" sound, this would be what I hear when it's playing (that whining/squealing), I guess that's the focus coil/springs? Can this be fixed? Does this cause skipping after first track? In the donor player, maybe due to being a cheapo one, even first track tends to skip (which it doesn't in Grundig).
- There's another strange thing, I noticed a crackling sound, like coming from the spindle motor. Also, when I turn the motor by hand, it seems not to rotate totally smooth. Could it really be the motor? Would that also explain why the disc was rubbing against the tray? But then again, the gap of the platter seems practically identical to the other cdms! Or, could the tray really have been damaged, rubbing against cd and having maybe the prior owner operated the player with the cd rubbing against the tray, if it was still reading, could this have damaged the spindle motor bearing? Would a damaged spindle motor bearing cause skipping that gets worse towards the end of the disc? I remember disc speed gets slower towards the end.
So, now I'm going to try something quite adventurous to be able to rule out the spindle motor: I'm going to take apart the swing arm and laser part of the "suspicious" cdm4 and also on one of the known good cdm4 players I have (I'll obviously try not to damage that player... so this is a bit risky) and swap them, so that I can test the laser and swing arm and also rule out that the spindle motor would be the cause. Let's see, I'll report back.
A question for who's got more experience than me:
can you see from a eye pattern on the scope if a laser is good or not?
In case the spindle motor experiment turns out impossible or doesn't solve anything. I mean, as I can get it to play track 1 almost free of skips, I could scope the eye pattern, but I don't really know how to interpret it (I know it should be crisp, clear and quite high in amplitude, but how high?).
- it's not the clamp ball bearing problem (exchanged the clamp with other players I have, also tried playing CD without clamp fixed with blue tac).
- gap between platter and deck is more or less identical to the other cdm-4s which I got and are working is about 1 mmm as Poynton said), still, when the tray is inserted, the disc is clearly scraping against it, you can even feel it when turning the clamped cd with your hands. This seems to be a problem related to the tray, I will compare with one of the cdm4s, which is a cheapo Philips which I got only as a donor for the laser mechanism to have a spare laser for my Marantz CD40, so I could eventually take its tray and adapt it to the Grundig, if the tray turns out to be damaged. But that's not all for now, more follows:
- with the tray taken out, cd is not touching the deck and spins freely, player immediately reads TOC (every time) (I fixed the CD with bostix, blue tack, whatever you call it).
BUT:
- player will read first track almost fine (maybe a couple of skips later), will jump to all tracks (pressed good condition CD), but from second track on it will skip more and more, as you approach further tracks, clearly you hear the laser whining, even on first track, I know that's clear indication that something is wrong.
- another thing I noted, I'm not sure it's normal: the swing arm doesn't rest about its middle position, it rests close to the platter (so at TOC position), is that normal? Both other cdm4s have the swing arm somewhere in the middle (one close to centre, the other perfectly in the middle of its travel), could that mean that there's a problem with the swing arm? But then I've google cdm-4 images and some do rest close to centre position. Swing arm moves freely.
- Now, as I have another player which is only donor for working cdm-4, I took that working unit out and installed the cdm-4 from the Grundig. It passes all service positions, radial swing arm moves well, focus is found immediately, laser seems to be fine (compared image through digital camera, red dot seems similar to red dot in other known good cdm-4's), but focus actions makes "squeak" sound, this would be what I hear when it's playing (that whining/squealing), I guess that's the focus coil/springs? Can this be fixed? Does this cause skipping after first track? In the donor player, maybe due to being a cheapo one, even first track tends to skip (which it doesn't in Grundig).
- There's another strange thing, I noticed a crackling sound, like coming from the spindle motor. Also, when I turn the motor by hand, it seems not to rotate totally smooth. Could it really be the motor? Would that also explain why the disc was rubbing against the tray? But then again, the gap of the platter seems practically identical to the other cdms! Or, could the tray really have been damaged, rubbing against cd and having maybe the prior owner operated the player with the cd rubbing against the tray, if it was still reading, could this have damaged the spindle motor bearing? Would a damaged spindle motor bearing cause skipping that gets worse towards the end of the disc? I remember disc speed gets slower towards the end.
So, now I'm going to try something quite adventurous to be able to rule out the spindle motor: I'm going to take apart the swing arm and laser part of the "suspicious" cdm4 and also on one of the known good cdm4 players I have (I'll obviously try not to damage that player... so this is a bit risky) and swap them, so that I can test the laser and swing arm and also rule out that the spindle motor would be the cause. Let's see, I'll report back.
A question for who's got more experience than me:
can you see from a eye pattern on the scope if a laser is good or not?
In case the spindle motor experiment turns out impossible or doesn't solve anything. I mean, as I can get it to play track 1 almost free of skips, I could scope the eye pattern, but I don't really know how to interpret it (I know it should be crisp, clear and quite high in amplitude, but how high?).
If it is catching on the deck, then the probable answer is that the drawer is not closing quite fully.
This means that the deck does not raise to the correct position.
Have you tried pushing the tray in?
Another possible cause of the noise is the focus and tracking mechanism working overtime.
The cause could be the infamous 33uF blue axial caps.
Look close to the cdm ribbon cable.
Replace with the SAME value not bigger as some are critical for time constants.
Andy
This means that the deck does not raise to the correct position.
Have you tried pushing the tray in?
Another possible cause of the noise is the focus and tracking mechanism working overtime.
The cause could be the infamous 33uF blue axial caps.
Look close to the cdm ribbon cable.
Replace with the SAME value not bigger as some are critical for time constants.
Andy
Thank you Andy for your suggestion in relation to the tray, I will check that out, but in case it has no solution, I have the spare tray from the other cheapo player.
Now, to the cdm which was misbehaving. First of all: seems that I managed to fix it !!! And yes, laser is absolutely fine, plays with no skips at all the whole disc. Haven't done thorough testing, though. Still some very faint whining noise close to disc end, though, but seems non-critical. What I did:
- I did the "RAFOC" swap (this is how the laser/swing arm element is called, right?) between known good and suspicious one, to be able to exclude the spindle motor.
It confirmed my worst fears: the spindle motor is fine, the problem was in the laser/swing arm. I carefully examined the known good one and the other and detected a problem I already had once with a CDM2: on the metal sheets that connect the lens to the focus coil (two parallel metal spring sheets) there has to be a tiny plastic sheet with a strange form, I will post photos later when I get more time. On this player, exactly like happened on the CDM2 (but there it happened in front of me and fell on my desk), the plastic thingie had fallen off (and in this case, vanished!), and not only one, both! It seems Philips used some not very good glue in those earlier CDMs, as the working CDMs I got here a bit newer and still have the plastic thingies well glued on.
I remembered from the CDM2 that it wouldn't read well with a lot of skips and whining noise when the plastic was off, once I glued the thingie on, the player went back to normal.
So, I figured I'd have to improvise. I got myself a thin plastic sheet from some packaging (it's more or less rigid and transparent, which is good so to be able to draw its shape from above), I figured it could have more or less the right weight (still not sure if that's to balance the metal springs or to stop the from oscillating??) and so I cut the shape out and then, dismanteling the upper lens to get access, glued them to the metal sheets with a tiny drop of superglue.
I took the opportunity to clean the inner lens.
Then put it all together (taking the opportunity to lube the small metal balls of the swing arm on both sides with a bit of special grease) and then I tested and YES, it works!
Really quick track changes, no skipping noticed, great music coming out headphones and plays until end of disc, a CD-R was also well played. No whining until more than half of the disc, from then it starts to appear, but only softly, I think it's non-critical, must be due to my improvised plastic thingies not having exactly the right shape and weight.
I will post photos later and also report from exhaustive tests (also report if I can fix the tray problem or use the spare tray), and then, if the player hopefully remains working great, I'll look into mods (this one is a nice opportunity for me, as I've not modded a TDA1543 yet, only TDA1541, and this one does not have that infamous Mitsubishi filters like some other 1543 based players, it used SAA7220.)
Now, to the cdm which was misbehaving. First of all: seems that I managed to fix it !!! And yes, laser is absolutely fine, plays with no skips at all the whole disc. Haven't done thorough testing, though. Still some very faint whining noise close to disc end, though, but seems non-critical. What I did:
- I did the "RAFOC" swap (this is how the laser/swing arm element is called, right?) between known good and suspicious one, to be able to exclude the spindle motor.
It confirmed my worst fears: the spindle motor is fine, the problem was in the laser/swing arm. I carefully examined the known good one and the other and detected a problem I already had once with a CDM2: on the metal sheets that connect the lens to the focus coil (two parallel metal spring sheets) there has to be a tiny plastic sheet with a strange form, I will post photos later when I get more time. On this player, exactly like happened on the CDM2 (but there it happened in front of me and fell on my desk), the plastic thingie had fallen off (and in this case, vanished!), and not only one, both! It seems Philips used some not very good glue in those earlier CDMs, as the working CDMs I got here a bit newer and still have the plastic thingies well glued on.
I remembered from the CDM2 that it wouldn't read well with a lot of skips and whining noise when the plastic was off, once I glued the thingie on, the player went back to normal.
So, I figured I'd have to improvise. I got myself a thin plastic sheet from some packaging (it's more or less rigid and transparent, which is good so to be able to draw its shape from above), I figured it could have more or less the right weight (still not sure if that's to balance the metal springs or to stop the from oscillating??) and so I cut the shape out and then, dismanteling the upper lens to get access, glued them to the metal sheets with a tiny drop of superglue.
I took the opportunity to clean the inner lens.
Then put it all together (taking the opportunity to lube the small metal balls of the swing arm on both sides with a bit of special grease) and then I tested and YES, it works!
Really quick track changes, no skipping noticed, great music coming out headphones and plays until end of disc, a CD-R was also well played. No whining until more than half of the disc, from then it starts to appear, but only softly, I think it's non-critical, must be due to my improvised plastic thingies not having exactly the right shape and weight.
I will post photos later and also report from exhaustive tests (also report if I can fix the tray problem or use the spare tray), and then, if the player hopefully remains working great, I'll look into mods (this one is a nice opportunity for me, as I've not modded a TDA1543 yet, only TDA1541, and this one does not have that infamous Mitsubishi filters like some other 1543 based players, it used SAA7220.)
So, while doing tests, this turned out to need much tweaking still, probably due to my "plastic thingie replica" not being perfect in balance/weight. But I did it. That's what was happening: the player was reading happily and well all and every disc, even scratched and old cdrs in bad shape, but depending on the quality of the disc (suppose it all has to do with balancing/precision), it would start to progressively whine more and more (and start to skip, I found out that a very little whining would be compensated by error correction) towards the end of discs, but from a certain amount of minutes onwards. First, it would do this starting from +-65 minutes on. I then found out that changing pressure on the disc centre would change things (for worse if more pressure), so I did bad things to the clamp spring, making it more soft, and yes, this did the trick (took me some tries, I didn't want to ruin it, although I do have a spare one), I also changed the inner part of the tray using the one from the el cheapo donor player, this fixed the problem with the tray, no more disc rubbing. I also discovered that the clamp from the cheapo player would result in less whining/skips than the one it came with, I don't know why, maybe it was in better (or worse?) shape. Maybe that ball bearing pit story. One more thing, very strange btw, I had to use only two screws diagonally in cross to fix the cdm to the deck, leaving the other two screws out, if I would put all four, it would start whining/skipping much earlier in most discs. Btw, I got the idea from one of the working cdm-4 players I have, it only has two screws fitted diagonally, and I think it has never been opened! Why's that? Design flaw?
In the end, I also exchanged the springs that support the cdm, using the ones from the cheapo player.
Obviously I also did the normal things (exchange that infamous blue Philips cap, verify laser adjustment and focus adjustment). Wrapping it up: it's almost perfect. It reads very well in terms of different types of discs/scratched discs, very quick toc recognition and track changes and it does read all discs of 74 minutes correctly through the end without whining or skips. Regarding 80 minutes discs it is still a bit picky: pressed discs are read until the end if they are in good shape, maybe starting to whine a little on the last track, but no skips. CD-Rs seem to be little more difficult (but I found out it depends on brand/age), some 80 minute ones it starts whining in the middle of the disc (this only happens with one specific brand, maybe the discs are defective, they are old), normally only starts having some trouble and sometimes starts to skip on some cd-rs starting from 77-78 minutes onwards. But I found a couple which flawlessly played until minute 80, so for me that's enough, it's fixed, it plays better than many other players thanks to the cdm and its laser which is in good shape, mechanically it's not as perfect as new, but well, it does have 33 years, right?
So, I'm happy as I saved another cdm from going towards the "spare parts bin".
Next thing, with time and no hurries, will be partial recap (power supply and a couple others, this player is a pain to mod due to difficult access, unless you take the whole PCB out) and some interesting mods which hopefully will improve the sound and let me appreciate the differences between tda1541 and 1543. It already sounds quite nice, btw.
Then I'm probably going to sell it (provided that it still passes all normal tests and continues to behave well, I'll make sure to play a lot of discs, so to be sure that the repair is really a lasting one, sometimes there are nasty surprises).
Photos:
1 - the RAFOC of the problematic cdm (missing the plastic thingies)
2- detail of the RAFOC of the good cdm-4, where you can see the edge of one of the plastic thingies (look close to the metal spring sheet), I didn't dismantle it, because I didn't want to risk the good cdm and also didn't want to waste time.
3 - one of the home made plastic thingies is now glued on.
4 - the top sheet still has no plastic thingie glued on (but you can see the glue residues! so this another way of knowing, if you find a cdm that's not working (but I guess they all use these plastic things, so if it's not there, it's broke).
5 - now with home made plastic sheet glued on.
Uff. This wasn't easy, I think a watch repair guy would feel at home doing this.
Hopefully this repair experience is going to help other people, as the damn plastic thingies seem to fall off quite often after some decades... this is the second CDM I come across with this, and they aren't even from the same model (one was CDM2, this is CDM4).
Also, another conclusion I was already aware of (but can't be said enough): the laser is the most unlikely part to fail in these CDMs, they are really good. So, please, please, keep these screwdrivers away from the laser adjustment pot!!! Save the lasers, they aren't made anymore (except for chinese copies).... If you have a CDM which is not working and you've given up and are just thinking about scrapping it, DON'T, send it to me lol, just kidding
In the end, I also exchanged the springs that support the cdm, using the ones from the cheapo player.
Obviously I also did the normal things (exchange that infamous blue Philips cap, verify laser adjustment and focus adjustment). Wrapping it up: it's almost perfect. It reads very well in terms of different types of discs/scratched discs, very quick toc recognition and track changes and it does read all discs of 74 minutes correctly through the end without whining or skips. Regarding 80 minutes discs it is still a bit picky: pressed discs are read until the end if they are in good shape, maybe starting to whine a little on the last track, but no skips. CD-Rs seem to be little more difficult (but I found out it depends on brand/age), some 80 minute ones it starts whining in the middle of the disc (this only happens with one specific brand, maybe the discs are defective, they are old), normally only starts having some trouble and sometimes starts to skip on some cd-rs starting from 77-78 minutes onwards. But I found a couple which flawlessly played until minute 80, so for me that's enough, it's fixed, it plays better than many other players thanks to the cdm and its laser which is in good shape, mechanically it's not as perfect as new, but well, it does have 33 years, right?
So, I'm happy as I saved another cdm from going towards the "spare parts bin".
Next thing, with time and no hurries, will be partial recap (power supply and a couple others, this player is a pain to mod due to difficult access, unless you take the whole PCB out) and some interesting mods which hopefully will improve the sound and let me appreciate the differences between tda1541 and 1543. It already sounds quite nice, btw.
Then I'm probably going to sell it (provided that it still passes all normal tests and continues to behave well, I'll make sure to play a lot of discs, so to be sure that the repair is really a lasting one, sometimes there are nasty surprises).
Photos:
1 - the RAFOC of the problematic cdm (missing the plastic thingies)
2- detail of the RAFOC of the good cdm-4, where you can see the edge of one of the plastic thingies (look close to the metal spring sheet), I didn't dismantle it, because I didn't want to risk the good cdm and also didn't want to waste time.
3 - one of the home made plastic thingies is now glued on.
4 - the top sheet still has no plastic thingie glued on (but you can see the glue residues! so this another way of knowing, if you find a cdm that's not working (but I guess they all use these plastic things, so if it's not there, it's broke).
5 - now with home made plastic sheet glued on.
Uff. This wasn't easy, I think a watch repair guy would feel at home doing this.
Hopefully this repair experience is going to help other people, as the damn plastic thingies seem to fall off quite often after some decades... this is the second CDM I come across with this, and they aren't even from the same model (one was CDM2, this is CDM4).
Also, another conclusion I was already aware of (but can't be said enough): the laser is the most unlikely part to fail in these CDMs, they are really good. So, please, please, keep these screwdrivers away from the laser adjustment pot!!! Save the lasers, they aren't made anymore (except for chinese copies).... If you have a CDM which is not working and you've given up and are just thinking about scrapping it, DON'T, send it to me lol, just kidding
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Well, this player is ready to go to a new caring owner. I'd really like to keep it, but I already have one beloved player (Marantz CD40 heavily modded) and am working on a new project as a second player (restoring Cambridge Audio D500SE with a new DAC) and still have to sell the second player I used before (Technics MASH)...
Below are some photos of what I did with it.
I made it Non-Oversampling, did a full recap, taking care to increase capacity of power supply filter caps (the analog supply +-15V I installed a couple of big 4700uF caps which I had lying around, they are the only not new caps but are still good (I tested them) so to filter it optimally. I added separate 7805 regulator dedicated only for TDA1543. I changed the output opamps for LM4562 and reduced the -3db point of the filter stage to avoid some of the HF stuff which gets added by NOS.
I also added a regulated +-9V supply around LM317/337 for CD mechanism and servos, etc, so I directly cut the +-10V rails where they come from the rectifier diodes and fed them with regulated clean +-9V supply. Last but not least I did a full new adjustment of laser current (now perfectly between 48 and 53 mV depending on disc) and focus offset. The latter turned out to be a large challenge (more on this later).
I had to discard the idea of adjusting focus offset to 400mV as in service manual instructions, because I figured that if the focus coils are not perfectly balanced due to my plastic thingies improvisation not being perfect, it might need a different focus offset. So, I tested different trimmer positions for the focus offset with quite a lot of CDs for several hours and also loading/starting and stopping to play them a lot of times (many I tried like 10 times in a row), as it has that strange behavior of sometimes rejecting to start playing a certain CD-R now and then (only to accept to play it immediately after hitting play again...) and also I had these two CD-Rs with 80 minutes which started to skip close to the end of the disc. This made it possible to settle on a sweet spot which seems to give best results. Far away from the 400mV. And yes, I did try a few different caps for the infamous blue philips axial laser filter cap, settled for a Nichicon 47uF, I didn't really noticed a difference here.
So, to the results. Firstly, it sounds great. Still a bit inferior to my Marantz (probably because that has a new clock fitted), but much better than before (more open, wider sound stage and more musical). (I won't go into the NOS/OS debate here. I've scoped the signals, I know they look strange stating from a few kHz, but to my ears it simply sounds much better in NOS than OS, I made my Marantz switchable between both but I don't bother, I always hear it in NOS). Sill want to do A/B testing because I'd like to get to know the particular differences between TDA1541 and 1543 (for now it seems the 1543 has a more powerful, warmer bass).
Second, it now reads much, much better than before. Don't know if due to new caps or due to the regulated supply. It reads TOC in about a second on most discs and track changes are lightning fast, even faster than on my well preserved Marantz or the Technics, which both use the same mechanism.
It also plays all pressed discs with over 74 minutes perfectly until the end, no whining, no skipping. No track change failures, either, not even on badly scratched CD-R.
It also plays all and every CD-R I throw at it, BUT: it still has the habit of refusing to start here and now, pretty much happens with 3/4 of all CD-Rs, none of the pressed CDs, though. When I say refuse, I mean it generally only happens once and it says Error when trying to play (TOC is read almost 100% of times, might have failed once). But then you hit Play again and most of the cases it plays immediately. Then there are some cases when it fails twice in a row to start and you have to repeat. But there are also cases where it starts to play immediately four times in a row, the same disc. And yes I had a couple of CD-Rs which it started to play flawlessly ten times in a row. So what's this? I don't know, but I think it's related to the repair I had to improvise (those two plastic thingies on the metal springs of the focus coil). As I said before, focus offset adjustment slightly improved things. But it doesn't bother me as it only happens now and then and is easily solved by pressing Play again, notice that the whole disc is then read flawlessly, track changes, everything. You can also put it into Pause and continue without trouble. And it ONLY happens with CD-Rs. I think it's related to the whining and skipping which still happens on a very few occasions and only on specific CD-Rs (not pressed CDs) after minute 77/78, more or less, which means I think the player looses focus due to the plastic thingies on the coil springs not being perfectly balanced. I think is also exatly the reason why it sometimes fails to start on a CD-R.
And yes, I checked eye pattern with scope, looks beautiful, no clipping and enough amplitude (1,2Vpp), so laser is fine.
That's it, just wanted to share the results. Some more testing and some A/B tests for me to know the TDA1543 before it's gone to some else's home.
I'd love to hear some opinions. (I know the way I've added the power regulators and the p2p-soldering and all is not the prettiest, but let me tell you, the inside of this player is NOT the best terrain for the happy modder... almost nothing fits there properly... if I wanted to do to this player what I did to my Marantz, it would be impossible.
Below are some photos of what I did with it.
I made it Non-Oversampling, did a full recap, taking care to increase capacity of power supply filter caps (the analog supply +-15V I installed a couple of big 4700uF caps which I had lying around, they are the only not new caps but are still good (I tested them) so to filter it optimally. I added separate 7805 regulator dedicated only for TDA1543. I changed the output opamps for LM4562 and reduced the -3db point of the filter stage to avoid some of the HF stuff which gets added by NOS.
I also added a regulated +-9V supply around LM317/337 for CD mechanism and servos, etc, so I directly cut the +-10V rails where they come from the rectifier diodes and fed them with regulated clean +-9V supply. Last but not least I did a full new adjustment of laser current (now perfectly between 48 and 53 mV depending on disc) and focus offset. The latter turned out to be a large challenge (more on this later).
I had to discard the idea of adjusting focus offset to 400mV as in service manual instructions, because I figured that if the focus coils are not perfectly balanced due to my plastic thingies improvisation not being perfect, it might need a different focus offset. So, I tested different trimmer positions for the focus offset with quite a lot of CDs for several hours and also loading/starting and stopping to play them a lot of times (many I tried like 10 times in a row), as it has that strange behavior of sometimes rejecting to start playing a certain CD-R now and then (only to accept to play it immediately after hitting play again...) and also I had these two CD-Rs with 80 minutes which started to skip close to the end of the disc. This made it possible to settle on a sweet spot which seems to give best results. Far away from the 400mV. And yes, I did try a few different caps for the infamous blue philips axial laser filter cap, settled for a Nichicon 47uF, I didn't really noticed a difference here.
So, to the results. Firstly, it sounds great. Still a bit inferior to my Marantz (probably because that has a new clock fitted), but much better than before (more open, wider sound stage and more musical). (I won't go into the NOS/OS debate here. I've scoped the signals, I know they look strange stating from a few kHz, but to my ears it simply sounds much better in NOS than OS, I made my Marantz switchable between both but I don't bother, I always hear it in NOS). Sill want to do A/B testing because I'd like to get to know the particular differences between TDA1541 and 1543 (for now it seems the 1543 has a more powerful, warmer bass).
Second, it now reads much, much better than before. Don't know if due to new caps or due to the regulated supply. It reads TOC in about a second on most discs and track changes are lightning fast, even faster than on my well preserved Marantz or the Technics, which both use the same mechanism.
It also plays all pressed discs with over 74 minutes perfectly until the end, no whining, no skipping. No track change failures, either, not even on badly scratched CD-R.
It also plays all and every CD-R I throw at it, BUT: it still has the habit of refusing to start here and now, pretty much happens with 3/4 of all CD-Rs, none of the pressed CDs, though. When I say refuse, I mean it generally only happens once and it says Error when trying to play (TOC is read almost 100% of times, might have failed once). But then you hit Play again and most of the cases it plays immediately. Then there are some cases when it fails twice in a row to start and you have to repeat. But there are also cases where it starts to play immediately four times in a row, the same disc. And yes I had a couple of CD-Rs which it started to play flawlessly ten times in a row. So what's this? I don't know, but I think it's related to the repair I had to improvise (those two plastic thingies on the metal springs of the focus coil). As I said before, focus offset adjustment slightly improved things. But it doesn't bother me as it only happens now and then and is easily solved by pressing Play again, notice that the whole disc is then read flawlessly, track changes, everything. You can also put it into Pause and continue without trouble. And it ONLY happens with CD-Rs. I think it's related to the whining and skipping which still happens on a very few occasions and only on specific CD-Rs (not pressed CDs) after minute 77/78, more or less, which means I think the player looses focus due to the plastic thingies on the coil springs not being perfectly balanced. I think is also exatly the reason why it sometimes fails to start on a CD-R.
And yes, I checked eye pattern with scope, looks beautiful, no clipping and enough amplitude (1,2Vpp), so laser is fine.
That's it, just wanted to share the results. Some more testing and some A/B tests for me to know the TDA1543 before it's gone to some else's home.
I'd love to hear some opinions. (I know the way I've added the power regulators and the p2p-soldering and all is not the prettiest, but let me tell you, the inside of this player is NOT the best terrain for the happy modder... almost nothing fits there properly... if I wanted to do to this player what I did to my Marantz, it would be impossible.
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Just wanted to add that I've been doing lots of tests with many different CD-Rs, starting ti play like each one ten times in a row and actually it fails to start playing much more rarely than I thought, in fact, most CD-Rs start to play all the time flawlessly, it's only a couple of specific CD-Rs, which fail to start like half of the time (though don't fail to start on the Marantz), they are all more than fifteen years old, so I think this is not really a problem at all, as all and every pressed CD I put in it is read always without problems and actually most CD-Rs, too. Really happy with this. Also, the sound is very, very interesting, I'm taking my time to listen to it and will do some comparison to my Marantz CD40 to try and spot the differences between the two TDAs (although not totally fair test, as opamps are different and the CD40 has a new clock, the Grundig doesn't, but still very interesting), so I won't be in a hurry to sell it. I'm liking it so much that I might even wait until finishing the Cambrigde to compare both and only then decide which one I keep as second player.
Thanks, but certainly I'm not a genius, I've got still a lot to learn.
The similarities to surgery have crossed my mind also, but I feel more it seems like eye surgery ahahah... as this is related to the laser... this is only scary when done for the first time, then you slowly get used to it
The similarities to surgery have crossed my mind also, but I feel more it seems like eye surgery ahahah... as this is related to the laser... this is only scary when done for the first time, then you slowly get used to it
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