Hard to say based on that although I still wouldn't automatically suspect the pickup at this point. Not if its all steady and OK when playing. Does the amplitude look correct? Typically 1.2 to 1.5v pp is a general figure for most players.
Depending on what is adjustable it might be worth going through the set up procedure and seeing if anything is on a knife edge. Normally a good player has loads of leeway in any of the servo adjustments.
It might also be worth confirming the PLL is correctly adjusted but refer to the manual and you would need a frequency counter to check.
Depending on what is adjustable it might be worth going through the set up procedure and seeing if anything is on a knife edge. Normally a good player has loads of leeway in any of the servo adjustments.
It might also be worth confirming the PLL is correctly adjusted but refer to the manual and you would need a frequency counter to check.
The amplitude looks correct once it settles down but it's very difficult to get it into that state and it seems to be deteriorating.
The service manual shows five pots that need to be adjusted as part of the setup procedure but it references an akai test disc to do this. The player has to be put into various test modes using the disc to do this. I tried a normal music CD but the disc starts to run at crazy speeds, so I don't think I can do it that way.
I can borrow a frequency counter from work to check the PLL but I do recall setting this before. Without the akai test disc I'm not sure I'll be able to make the other adjustments though.
One other thing that is happening is I must wait for the disc to stop spinning before I press eject or the tray comes out with a rapid spinning disc still on it.
I'm starting to wonder if this player really has had it's day now. After all the previous work with reflowing boards and new parts, it's still only worked for a few months with very light use.
The service manual shows five pots that need to be adjusted as part of the setup procedure but it references an akai test disc to do this. The player has to be put into various test modes using the disc to do this. I tried a normal music CD but the disc starts to run at crazy speeds, so I don't think I can do it that way.
I can borrow a frequency counter from work to check the PLL but I do recall setting this before. Without the akai test disc I'm not sure I'll be able to make the other adjustments though.
One other thing that is happening is I must wait for the disc to stop spinning before I press eject or the tray comes out with a rapid spinning disc still on it.
I'm starting to wonder if this player really has had it's day now. After all the previous work with reflowing boards and new parts, it's still only worked for a few months with very light use.
I finally got it to start playing again by going from track to track. My scope can measure frequency and the PLL is locked at 7.35kHz as shown in the manual which is one win.
If I skip a track it starts misbehaving again and the PLL starts jumping around in frequency but I think this is an effect of the fault rather than the cause?
If I skip a track it starts misbehaving again and the PLL starts jumping around in frequency but I think this is an effect of the fault rather than the cause?
The PLL should normally be free running close to the correct frequency. The 7.8kHz isn't the raw PLL which typically runs at something like 4.3218Mhz Not all players have an an adjustment but many do.
There isn't anything RF signal wise on a typical test disc that is different to a standard Red Book pressed CD. They are just discs made to a very high and defined spec for things like reflectivity and runout and so on but as far as RF goes any representative music disc should be fine.
There isn't anything RF signal wise on a typical test disc that is different to a standard Red Book pressed CD. They are just discs made to a very high and defined spec for things like reflectivity and runout and so on but as far as RF goes any representative music disc should be fine.
If it does that from just normal play mode when the RF is stable then it does suggest something else might be going on
Given the huge amount of time and effort already spent on this unit for relatively little use in return, I'm finding difficult to find enthusiasm for any further work on it.
Intermittent faults are always the worst and the way this one is constructed makes it very difficult to work on. I think I'll call time on it for now until I can find some further inspiration.
Intermittent faults are always the worst and the way this one is constructed makes it very difficult to work on. I think I'll call time on it for now until I can find some further inspiration.
Been there and done that before
Either scrap the unit... whack it, dismantle it, bin and then its out of mind with no going back, or approach it with a 'doesn't matter' attitude and try whatever you want. Increase the laser power by a decent amount to raise the RF by say 10 or 15% and give the unit another setup. If its driving you nutz then just call time on it.
Its not often I say that but sometimes its the best option and you can concentrate on other stuff.
I've also been here before with other devices. I'm not quite at the point where I'm ready to whack it and bin it, although I know how satisfying that can be for a brief moment!
I tried tweaking each pot 10% or so each way to see if it made any difference with the 'doesn't matter' now attitude but with no improvement.
I'll probably put it to one side for now until I get a rainy winter weekend when there's nothing on tv and I have more spare time.
I tried tweaking each pot 10% or so each way to see if it made any difference with the 'doesn't matter' now attitude but with no improvement.
I'll probably put it to one side for now until I get a rainy winter weekend when there's nothing on tv and I have more spare time.
@andyb1712
I think the problem still lies with the sense coil on the sled. The fact that the machine still plays well when it somehow does, and that when it does you have good RF waveform indicates the laser is good, the focus servo is good, the CLV servo is good. The questionable part is then the tracking servo, which the linear drive sled is big part of, which we have a failing sense coil within. When you fast-forward or skip a sound track or seek a sound track, you're asking the tracking servo to perform a much more dynamic task than would during normal playback. These seem to be the moment the operation would fail from your description, and a symptom consistent with the above suspicion.
The shorting wire mod that seemed to have "worked" did not fix anything, other than fooling the micro-controller into not seeing a failing sense coil and, consequently not performing its safe-guard duty refusing loading the disc. The performance of the linear sled drive system might have been borderline yet could keep the machine going for a while, and when the sense coil deteriorated further, we have a non-usable machine eventually.
If you happen to become strong-willed enough and want to get to the bottom of it, I guess there is no way around that sense coil. Replacing it, or rewinding it would be the only way to go I'm afraid.
I would set it aside, turn the page and move on. You have had all your music collections on HDD you have nothing to lose. I used mine for perhaps less than 20 hours in the past 10 years and did not miss it at all ...well except the very nimble playback controls.
I think the problem still lies with the sense coil on the sled. The fact that the machine still plays well when it somehow does, and that when it does you have good RF waveform indicates the laser is good, the focus servo is good, the CLV servo is good. The questionable part is then the tracking servo, which the linear drive sled is big part of, which we have a failing sense coil within. When you fast-forward or skip a sound track or seek a sound track, you're asking the tracking servo to perform a much more dynamic task than would during normal playback. These seem to be the moment the operation would fail from your description, and a symptom consistent with the above suspicion.
The shorting wire mod that seemed to have "worked" did not fix anything, other than fooling the micro-controller into not seeing a failing sense coil and, consequently not performing its safe-guard duty refusing loading the disc. The performance of the linear sled drive system might have been borderline yet could keep the machine going for a while, and when the sense coil deteriorated further, we have a non-usable machine eventually.
If you happen to become strong-willed enough and want to get to the bottom of it, I guess there is no way around that sense coil. Replacing it, or rewinding it
would be the only way to go I'm afraid.I would set it aside, turn the page and move on. You have had all your music collections on HDD you have nothing to lose. I used mine for perhaps less than 20 hours in the past 10 years and did not miss it at all ...well except the very nimble playback controls.
Thanks for the detailed reply on this one. What you say makes sense because the original problem was never really fixed. It was a work around and it may well be the coil has deteriorated further resulting in further problems.
Rewinding the coil may not be such an impossible task... the place I work has coil winding facilities but it will depend if they have fine enough wire for this particular job. It's something I can look into.
As you say, my music collection is mostly digitized now for convenience. so the CD player doesn't see much use now but it is still a nice piece of kit when working. If it's repairable I will probably try again but for now it's put to one side.
Rewinding the coil may not be such an impossible task... the place I work has coil winding facilities but it will depend if they have fine enough wire for this particular job. It's something I can look into.
As you say, my music collection is mostly digitized now for convenience. so the CD player doesn't see much use now but it is still a nice piece of kit when working. If it's repairable I will probably try again but for now it's put to one side.
In case it ever becomes useful, this chart may help make a reasonable guess about the wire size by using the ohms/gram column. As the wire is extremely thin and there can be a substantial length of it, measuring the total weight is probably more practical than measuring the total length.
It would take a fairly precise electronic scale to weigh out the magnet wire unwound from the bobbin. The scale I make espresso with has resolution of 0.01g and it's inexpensive. Or, take the unwound wire to a jeweler.
It would take a fairly precise electronic scale to weigh out the magnet wire unwound from the bobbin. The scale I make espresso with has resolution of 0.01g and it's inexpensive. Or, take the unwound wire to a jeweler
.Just read through the topic. Hats off, gentlemen. I have a CD73 too wich has already been repaired with an open sense coil. I Just got it in this state, it is been told that only one turn of wire has been removed and the failure was there, so it was an easy fix. Yet we have to find out what deteriorates the wire, as it can happens anytime again and doing a rewire on it looks a bit painful job with a lot of words like most Rap stars are eager to tell.
On mine also the tr3 mod is done, but yet to find out if it is required or the sense coil repair may be enough in itself (didn't measure because fórum was offline yesterday evening). Player works, I must amit it has beautiful sound and quite an appealing appearance.
But will have to do some more work, just see what I have cleaned around the lens-and had to clean and relube sled shaft, clamp lock and so on.
On mine also the tr3 mod is done, but yet to find out if it is required or the sense coil repair may be enough in itself (didn't measure because fórum was offline yesterday evening). Player works, I must amit it has beautiful sound and quite an appealing appearance.
But will have to do some more work, just see what I have cleaned around the lens-and had to clean and relube sled shaft, clamp lock and so on.
Attachments
I have two points.
First, the LMI input that is fed by TR3 doesn't look like a safety solution at fiorst. In the SM it says linear motor moving direction and it is H when the sled moves inward. It is evident from the comparator IC10 too: its output changes to H when the voltage generated on the sensing coil is positive wich happens when it moves invard. That happens normally at every moment when the sledge moves to the beginning of the disc and can maybe used for detecting something, but i don't think it is a good protection against anything-since when sledge moves outwards, there is no any sign for the micom it does it with too high speed. From my view the necessity of LMI input remains a mystery.
For the wire fault on sensor coil, my first idea is the glue of the foil used for covering the coil itself and if it is really an issue, then we have luck, as not much wire is affected and that is found on the outer windings..
First, the LMI input that is fed by TR3 doesn't look like a safety solution at fiorst. In the SM it says linear motor moving direction and it is H when the sled moves inward. It is evident from the comparator IC10 too: its output changes to H when the voltage generated on the sensing coil is positive wich happens when it moves invard. That happens normally at every moment when the sledge moves to the beginning of the disc and can maybe used for detecting something, but i don't think it is a good protection against anything-since when sledge moves outwards, there is no any sign for the micom it does it with too high speed. From my view the necessity of LMI input remains a mystery.
For the wire fault on sensor coil, my first idea is the glue of the foil used for covering the coil itself and if it is really an issue, then we have luck, as not much wire is affected and that is found on the outer windings..
I read the most recent posts with great interest. I put my CD73 back into storage after it stopped working again. I haven't got around to looking at the sense coil again but if it is just a break in the wire in the first few turns, then it would seem a good time to take another look at it. If that is indeed the case, then removing a few turns doesn't seem like a bad idea to get it working.
Don't! such hairwire windings can be rewound too. I have a friend who is making pickup coils. I can ask him. There was a thread about possible wire diameter. And I also have to note that KSS272A has around the same resistance sense coil (3,5k measured), and it seems unaffected by the problem-I was able to separate and reconnect without any issue. So it looks like we still have possibilities, don't give up! Sound is very good from this player.
such hairwire windings can be rewound too. I have a friend who is making pickup coils. I can ask him. There was a thread about possible wire diameter. And I also have to note that KSS272A has around the same resistance sense coil (3,5k measured), and it seems unaffected by the problem-I was able to separate and reconnect without any issue. So it looks like we still have possibilities, don't give up! Sound is very good from this player.My attempts to locate the end of the wire to reconnect it failed over and over... the more I tried, the more damage I did. I have now removed all of the wire from the coil former so I can weigh it. This was previously suggested as a better way to determine the amount of wire required.
I have reassembled the player mech for now so no parts are lost but then the main on/off power switch failed too. I found a suitable donor from a scrap Onkyo amp, which I have fitted and works well.
There is some coil winding equipment where I work, so I will look into getting some suitable wire and see if I am able to do this. It certainly doesn't look like an easy task!
I have reassembled the player mech for now so no parts are lost but then the main on/off power switch failed too. I found a suitable donor from a scrap Onkyo amp, which I have fitted and works well.
There is some coil winding equipment where I work, so I will look into getting some suitable wire and see if I am able to do this. It certainly doesn't look like an easy task!