Having finally found a solution to the loading tray problem on my Akai CD-73, I now know it requires a replacement sense coil for the laser mechanism.
This uses the KSS-151A pickup and seems to be common in a number of Sony, Teac and Denon players as well as the Akai 73 and 93.
If anyone has a player with a dead pickup/mechanism that would like to sell the sense coil, please send me a message.
My player is working again with a modification to get around the problem but I have no idea if or when this coil will fail completely and it will stop working again.
This uses the KSS-151A pickup and seems to be common in a number of Sony, Teac and Denon players as well as the Akai 73 and 93.
If anyone has a player with a dead pickup/mechanism that would like to sell the sense coil, please send me a message.
My player is working again with a modification to get around the problem but I have no idea if or when this coil will fail completely and it will stop working again.
Hi Andy - I read the hard-trodden story of the ultimate workaround for the jiggy door problem with great interest, I had been in the same boat with my CD-93. Albeit, mine would read the TOC, but never play whatsoever, unless inclined / linear motor 'helped' by gravity.
Happily, with a lot of headscratching, many checks made after some daunting disassembly / reassembly to get to the back of both boards (!), and the info in your posts, I got back to some form of successful operation - door calmed, basic operation, but....
In my case, the laser is all fine too as is the linear motor, but my sensor coil was completely open circuit. It had the effect of screwing up the voltages around the drive and feedback circuit(s), and as far as I can tell was leading to insufficient drive out of the transistor pair which powers the sled. I guess it must be some sort of fail-safe to just cut power to the drive if the feedback circuit is suspect. Whilst I can't claim to fully comprehend the circuitry in and around the drive / sensor feedback (I truly wish I could!), introducing a resistor in the 23k - 27k range, in place of the (open) sensor coil, has brought back just enough drive for the sled to operate successfully. (I assume the sensor coil is constantly feeding back and influencing the drive voltage...so, at least moving away from open circuit has brought things partly back to life...)
But, as was indicated by respondents (far more expert than me!) in your topic, the linear drive needs correct feedback operation to work properly, otherwise as I am finding it overshoots on operations like track selection / skipping. It will however play all the way through a CD and function with the slow search forwards and backwards.
So, to restore my CD-93 to normal functioning and tame the uncontrolled / over accelerated sled motion - like you, I'm thinking I really need that sensor coil replacing too.
It's strange to see so many KSS-151A owners, searching far and wide for lasers, when what's wrong with these jiggy-door Akai's mostly seems to be sensor coils, but nobody seems to be clearing the salvaged mechs after ripping off the lasers!?
Did you ever find a sensor coil, and if so could you point me to someone that could help me out too?
Many thanks for the invaluable info in your recount, and any other pointers you could offer. 👍
Happily, with a lot of headscratching, many checks made after some daunting disassembly / reassembly to get to the back of both boards (!), and the info in your posts, I got back to some form of successful operation - door calmed, basic operation, but....
In my case, the laser is all fine too as is the linear motor, but my sensor coil was completely open circuit. It had the effect of screwing up the voltages around the drive and feedback circuit(s), and as far as I can tell was leading to insufficient drive out of the transistor pair which powers the sled. I guess it must be some sort of fail-safe to just cut power to the drive if the feedback circuit is suspect. Whilst I can't claim to fully comprehend the circuitry in and around the drive / sensor feedback (I truly wish I could!), introducing a resistor in the 23k - 27k range, in place of the (open) sensor coil, has brought back just enough drive for the sled to operate successfully. (I assume the sensor coil is constantly feeding back and influencing the drive voltage...so, at least moving away from open circuit has brought things partly back to life...)
But, as was indicated by respondents (far more expert than me!) in your topic, the linear drive needs correct feedback operation to work properly, otherwise as I am finding it overshoots on operations like track selection / skipping. It will however play all the way through a CD and function with the slow search forwards and backwards.
So, to restore my CD-93 to normal functioning and tame the uncontrolled / over accelerated sled motion - like you, I'm thinking I really need that sensor coil replacing too.
It's strange to see so many KSS-151A owners, searching far and wide for lasers, when what's wrong with these jiggy-door Akai's mostly seems to be sensor coils, but nobody seems to be clearing the salvaged mechs after ripping off the lasers!?
Did you ever find a sensor coil, and if so could you point me to someone that could help me out too?
Many thanks for the invaluable info in your recount, and any other pointers you could offer. 👍
Congratulations for a successful diagnosis of the infamous Akai CD-73/93 “tray oscillation” failure.
I had been concentrating on several large “non-audio” projects for the past 1.5 years so I didn’t read the “digital source” postings at DIY audio until a couple of days ago.
This issue with the sled “sense coil” going open-circuit when the unit reaches an advanced age (30 years?) could explain why this particular fault suddenly appeared in so many examples of these 2 Akai models.
The wire with which the sense coil is wound is extremely thin. Also this coil has many turns of wire in it. This increases the odds of “open-circuit” faults.
I own one CD player which probably contains a similar “linear sled drive.” It is a Denon DCD-1500 II. I haven’t used it recently. I will give it a whirl and see if it is still functional. It will be interesting to compare the Denon sled drive circuitry to what Akai used. I have service manuals and schematics for both models.
The remaining question is: “How does one make a functional replacement for the open-circuit sense coil?”
Electric guitar pickups are wound with many turns of very fine wire. Studying forum discussions from people who make and modify guitar pickups might shed some light on this.
There also may be other ways to get the sled servo working well which don’t require the sense coil. It is noteworthy that these machines are still able to play discs without a functional sense coil.
I had been concentrating on several large “non-audio” projects for the past 1.5 years so I didn’t read the “digital source” postings at DIY audio until a couple of days ago.
This issue with the sled “sense coil” going open-circuit when the unit reaches an advanced age (30 years?) could explain why this particular fault suddenly appeared in so many examples of these 2 Akai models.
The wire with which the sense coil is wound is extremely thin. Also this coil has many turns of wire in it. This increases the odds of “open-circuit” faults.
I own one CD player which probably contains a similar “linear sled drive.” It is a Denon DCD-1500 II. I haven’t used it recently. I will give it a whirl and see if it is still functional. It will be interesting to compare the Denon sled drive circuitry to what Akai used. I have service manuals and schematics for both models.
The remaining question is: “How does one make a functional replacement for the open-circuit sense coil?”
Electric guitar pickups are wound with many turns of very fine wire. Studying forum discussions from people who make and modify guitar pickups might shed some light on this.
There also may be other ways to get the sled servo working well which don’t require the sense coil. It is noteworthy that these machines are still able to play discs without a functional sense coil.
Thank you for your responses and suggestions. The primary fault I have clearly appears to be the sensor coil (which supplies the feedback signal to help control the linear drive).
The only repair alternatives seem to be i) fit a new identical replacement coil (unlikely to be sourceable), ii) salvage a good coil / drive from a good unit, iii) repair the existing coil.
Option i) is very unlikely from first attempts, ii) is possible but probably as costly as a salvaged entire laser and drive, iii) could be the best option.
The coil is quite removable from the linear drive with moderate disassembly, so I took mine out for a closer look. Like HF loudspeaker units these appear to have a tendency to fail first on the section of wire trailing out both ends to the solder terminals - one or both of mine had gone here. Once was still accessible with tweezers, and I was able to successfully take off one wind and refix. The other was unfortunately not accessible, so I fished around gently and found what seemed to be a loose end. I connected all back, and regained continuity - unfortunately at a much lower coil resistance (around 0.15kohms) than other contributors have suggested is correct (3.16kohm). So, I must have either damaged the coil and broken out another 'end' of the winding and / or it's shorter somewhere - most likely the former. I tried it, and sure enough the door issue was tamed, without the TR3 grounding mod....but, the control was not there, sled just moving too wildly. I guess this probably illustrates a lack of voltage being induced in the sensor coil, due to the insufficient (less than 5%?) windings still in play.
So, the guitar pickups pointer from electricboyo is now looking most helpful, thank you. I'm thinking about a repair of the coil, it's pretty simple construction, albeit very fine winding, as observed - I shall look into it. I may try rewinding it myself (!) and / or approach a friendly guitar pickup winder 😊.
In the meantime, if anyone happens to have a spare sensor coil / KSS 151a drive in a drawer - a 151a mech perhaps discarded due to a broken laser, please do get in touch and let me know. That one simple part from the drive-mech would be a great help in this case.
All the best and once again, thanks.
The only repair alternatives seem to be i) fit a new identical replacement coil (unlikely to be sourceable), ii) salvage a good coil / drive from a good unit, iii) repair the existing coil.
Option i) is very unlikely from first attempts, ii) is possible but probably as costly as a salvaged entire laser and drive, iii) could be the best option.
The coil is quite removable from the linear drive with moderate disassembly, so I took mine out for a closer look. Like HF loudspeaker units these appear to have a tendency to fail first on the section of wire trailing out both ends to the solder terminals - one or both of mine had gone here. Once was still accessible with tweezers, and I was able to successfully take off one wind and refix. The other was unfortunately not accessible, so I fished around gently and found what seemed to be a loose end. I connected all back, and regained continuity - unfortunately at a much lower coil resistance (around 0.15kohms) than other contributors have suggested is correct (3.16kohm). So, I must have either damaged the coil and broken out another 'end' of the winding and / or it's shorter somewhere - most likely the former. I tried it, and sure enough the door issue was tamed, without the TR3 grounding mod....but, the control was not there, sled just moving too wildly. I guess this probably illustrates a lack of voltage being induced in the sensor coil, due to the insufficient (less than 5%?) windings still in play.
So, the guitar pickups pointer from electricboyo is now looking most helpful, thank you. I'm thinking about a repair of the coil, it's pretty simple construction, albeit very fine winding, as observed - I shall look into it. I may try rewinding it myself (!) and / or approach a friendly guitar pickup winder 😊.
In the meantime, if anyone happens to have a spare sensor coil / KSS 151a drive in a drawer - a 151a mech perhaps discarded due to a broken laser, please do get in touch and let me know. That one simple part from the drive-mech would be a great help in this case.
All the best and once again, thanks.
I also removed the sense coil from my Akai to try and repair it but failed for the same reasons. My plan was to try and rewind it or get someone to do it for me but so far I haven't done any more with it.
The wire for the Akai coil is, I think, 0.04mm diameter, which is available but very fine and easily broken. Winding this isn't going to be an easy job and beyond my skills.
I have now replaced the Akai with a nearly new Onkyo, which sounds nice and is fully working so I don't know if the Akai will ever be repaired.
The wire for the Akai coil is, I think, 0.04mm diameter, which is available but very fine and easily broken. Winding this isn't going to be an easy job and beyond my skills.
I have now replaced the Akai with a nearly new Onkyo, which sounds nice and is fully working so I don't know if the Akai will ever be repaired.