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.
I have two DCD1500II and both have requested a disassembly of the pcbs to redo the solders and replace some capacitors to be perfectly operational.
Good luck
Good luck
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.
Just wanted to reply to this at long last, apologies for the lengthy delay since I last worked on the CD-93, with success, just under two years ago. It has worked without fault, ever since and seems absolutely reliable following the sensor coil repair. There have been many very learned, excellent and way more expert postings than mine above, thank you so much to ALL.
There are truly impressive steps taken in these vintage Akai's to raise performance to a very high level for it's time - fully cast alloy chassis, copper shielding, large separate potted transformers for digital and analogue circuits, the KSS-151a mech, very nice steel spring transport suspension system, full diameter disc clamping, direct drive spindle motor with mounting castings, copper shielded circuit boards, quality components, large oversized display, to name a few...it's clear they really tried to go above and beyond at the time on some of the basics. In construction terms, it is way up there with the very best contemporaries of Philips, Marantz, Sony...etc
Basically, if it is the common sensor fault (confirmed by checking for the shorted linear motion feedback coil), then it IS - with some challenge - repairable.
And, what's more it really is worth it. I have now listened to the unmodified CD-93 on multiple (pretty decent) setups and to my ears it has consistently genuinely audibly outperformed, in some cases by some margin, a standard CD960, clocked CD-94, various standard Denon DCD-15XX series, unmodified Sony ESDs 227 / 337 / 338 / 555, and even in many respects bettered a well modified TEAC VRDS 25x, to name a few. It's most striking strengths are the tonal balance / textural realism, spacial cues, realistic dynamics and the ability to keep separate musical lines delineated and under control when it gets busy or tough - classic cues for good digital or analogue playback equipment, whatever the DAC or type of music. It's clearly been listened to alot originally, by the designers. In addition, it has an uncommonly deep (low) bass ability, the sort that is more 'ambient' than headbanging and often only heard with larger speakers. Basically, it's a very unusual, heavily engineered, somewhat quirky, but highly capable machine! They clearly missed or underestimated some reliability problems which meant there were sadly a handful of overly common failure modes. Also, heat should have probably been managed better. But, from listening to it, I encourage everyone to not give up on the pulsating door / linear sled sensor fault / coil repair, if you can try...☺️
In my case, I removed the sensor coil completely several times in the course of repairs (requires some careful disassembly of the Akai linear motor / sensor assembly for the KSS-151a, easier than in some other Sony's). Initially I hoped a sensor coil from say a similar KSS-151a Sony or Denon might be substitutable as they looked very similar. Alas, the dimensions are different and electrically I suspect they measure differently - only the Akai's sensor coil body seems to suit the Akai magnet / rail. So, once the coil was off, under magnification I looked for any obvious break near either terminals (the coil wires mount to the same terminal as the ribbon tape does). Maybe just unwind a turn and therefore an easier fix for some?? Nothing was obvious in my case. So, I opted for gradually unravelling the coil to find a break. I eventually found a the break and as a first attempt tried to resolder the remaining (shortened coil). After some real difficulty with such fine wire (and some degree of inexperience!) , it was eventually reconnected. It measured badly now but nonetheless, when tested (with the discussed resistor mod removed) it likewise tamed the door fault. The CD now went on to read too, but the sled was prone to significantly over-shooting during track selections and playback tracking. Sled control was now well out of calibration, due to the amended / shortened sensor coil. I could not see any easy way to compensate electrically, I tried adding the resistor mod partially, also some resistance in series as a looksee - as expected it didn't make up for the (now) incorrect sensor coil. Resistance adjustments (with a resistor in line) either just killed the motion totally or left it uncontrolled. It needs roughly the correct sensor coil...
So, I decided to attempt to get some wire and wind (my first ever!) coil. I noted the winding direction and relevant terminals (important!), then removed the original wire and measured the total length as best as possible. I then tried to get some resistance and length measurements and ***** the wire guage required from basic maths and visuals. I had nothing to compare too and no other estimate posted at that point. It was approximate and I could not risk going too low on the wire-guage as I understood it would probably be impossible without a proper winding rig, by hand. So, I went for as low as I dared, 0.056mm, and probably the lowest guage I could easily source. I figured I would just wind as close to the original number of turns as possible, and see how it worked out back in use! I used an online calculator I found via google to help approximate the number of turns on the original coil Vs the resistance required with the DIY winding, so I could count / measure when winding. If it worked I could always get something more accurate and better made...maybe somewhere?! I figured, as the unit was not operating anyway, then any working linear motion feedback system for the sled would be better than none, as long as it got close enough when travelling the electronics would likely control it well enough to let the laser home-in, and it didn't need to be as perfect as, say, a voicecoil, with the incredibly tight clearances and tolerance, which affects performance and matching alot. Clearance required for this coil is not a problem, it can even be a bit messy, worst case, as long as the winding has enough, tidy enough, turns in the right direction
Once the sensor coil was again removed and stripped of all original wire. I found the right size insert / rod to act as a (very) basic coil-body holder to insert into a held-down, handheld drill, feeding wire from the reel held on a stick between the knees! The wire broke many times the first 10 mins I tried, it was so fine. I got better, adjusted the speeds and angles to minimise the strain on the fine wire, learnt how best to let it slide / guide multiple passes, with just enough tension. I had a fair few failed attempts in the beginning and had to remove and restart. Eventually, I had a run which was about 80% of what I had calculated as required turns / resistance. I could have persevered to get the perfect run, but I decided to give it a go, as it was...
...basically, it worked straight away. It didn't even need any adjustments.
The CD player hasn't missed a beat since, whenever I've used it over the past 2 years. It sometimes won't read my toughest copied disc, but it is as reliable a reader now as every other unit of this vintage on original disks and most copies, and way better than some later CD-rom type readers!
I'd have probably never understood how to identify and get at the fault without everyone else's explanation, so once again thanks. The sensor coil fix, coil-winding is a challenge, but it is DIY-do-able, and truly worth the effort with the Akai.
I'd wholeheartedly recommend the sound of the CD-93. It's genuinely, surprisingly good and definitely outshines most of its contemporaries in stock form, albeit they , are more well known, widely available and listened to! Looking back, it seems it was an expensive player in its time and so, when there is common but quirky, tricky fault, unsurprisingly they are quite rare and there are not so many around.
In short, I've found it very reliable and high-performing, since the repair.
There are truly impressive steps taken in these vintage Akai's to raise performance to a very high level for it's time - fully cast alloy chassis, copper shielding, large separate potted transformers for digital and analogue circuits, the KSS-151a mech, very nice steel spring transport suspension system, full diameter disc clamping, direct drive spindle motor with mounting castings, copper shielded circuit boards, quality components, large oversized display, to name a few...it's clear they really tried to go above and beyond at the time on some of the basics. In construction terms, it is way up there with the very best contemporaries of Philips, Marantz, Sony...etc
Basically, if it is the common sensor fault (confirmed by checking for the shorted linear motion feedback coil), then it IS - with some challenge - repairable.
And, what's more it really is worth it. I have now listened to the unmodified CD-93 on multiple (pretty decent) setups and to my ears it has consistently genuinely audibly outperformed, in some cases by some margin, a standard CD960, clocked CD-94, various standard Denon DCD-15XX series, unmodified Sony ESDs 227 / 337 / 338 / 555, and even in many respects bettered a well modified TEAC VRDS 25x, to name a few. It's most striking strengths are the tonal balance / textural realism, spacial cues, realistic dynamics and the ability to keep separate musical lines delineated and under control when it gets busy or tough - classic cues for good digital or analogue playback equipment, whatever the DAC or type of music. It's clearly been listened to alot originally, by the designers. In addition, it has an uncommonly deep (low) bass ability, the sort that is more 'ambient' than headbanging and often only heard with larger speakers. Basically, it's a very unusual, heavily engineered, somewhat quirky, but highly capable machine! They clearly missed or underestimated some reliability problems which meant there were sadly a handful of overly common failure modes. Also, heat should have probably been managed better. But, from listening to it, I encourage everyone to not give up on the pulsating door / linear sled sensor fault / coil repair, if you can try...☺️
In my case, I removed the sensor coil completely several times in the course of repairs (requires some careful disassembly of the Akai linear motor / sensor assembly for the KSS-151a, easier than in some other Sony's). Initially I hoped a sensor coil from say a similar KSS-151a Sony or Denon might be substitutable as they looked very similar. Alas, the dimensions are different and electrically I suspect they measure differently - only the Akai's sensor coil body seems to suit the Akai magnet / rail. So, once the coil was off, under magnification I looked for any obvious break near either terminals (the coil wires mount to the same terminal as the ribbon tape does). Maybe just unwind a turn and therefore an easier fix for some?? Nothing was obvious in my case. So, I opted for gradually unravelling the coil to find a break. I eventually found a the break and as a first attempt tried to resolder the remaining (shortened coil). After some real difficulty with such fine wire (and some degree of inexperience!) , it was eventually reconnected. It measured badly now but nonetheless, when tested (with the discussed resistor mod removed) it likewise tamed the door fault. The CD now went on to read too, but the sled was prone to significantly over-shooting during track selections and playback tracking. Sled control was now well out of calibration, due to the amended / shortened sensor coil. I could not see any easy way to compensate electrically, I tried adding the resistor mod partially, also some resistance in series as a looksee - as expected it didn't make up for the (now) incorrect sensor coil. Resistance adjustments (with a resistor in line) either just killed the motion totally or left it uncontrolled. It needs roughly the correct sensor coil...
So, I decided to attempt to get some wire and wind (my first ever!) coil. I noted the winding direction and relevant terminals (important!), then removed the original wire and measured the total length as best as possible. I then tried to get some resistance and length measurements and ***** the wire guage required from basic maths and visuals. I had nothing to compare too and no other estimate posted at that point. It was approximate and I could not risk going too low on the wire-guage as I understood it would probably be impossible without a proper winding rig, by hand. So, I went for as low as I dared, 0.056mm, and probably the lowest guage I could easily source. I figured I would just wind as close to the original number of turns as possible, and see how it worked out back in use! I used an online calculator I found via google to help approximate the number of turns on the original coil Vs the resistance required with the DIY winding, so I could count / measure when winding. If it worked I could always get something more accurate and better made...maybe somewhere?! I figured, as the unit was not operating anyway, then any working linear motion feedback system for the sled would be better than none, as long as it got close enough when travelling the electronics would likely control it well enough to let the laser home-in, and it didn't need to be as perfect as, say, a voicecoil, with the incredibly tight clearances and tolerance, which affects performance and matching alot. Clearance required for this coil is not a problem, it can even be a bit messy, worst case, as long as the winding has enough, tidy enough, turns in the right direction
Once the sensor coil was again removed and stripped of all original wire. I found the right size insert / rod to act as a (very) basic coil-body holder to insert into a held-down, handheld drill, feeding wire from the reel held on a stick between the knees! The wire broke many times the first 10 mins I tried, it was so fine. I got better, adjusted the speeds and angles to minimise the strain on the fine wire, learnt how best to let it slide / guide multiple passes, with just enough tension. I had a fair few failed attempts in the beginning and had to remove and restart. Eventually, I had a run which was about 80% of what I had calculated as required turns / resistance. I could have persevered to get the perfect run, but I decided to give it a go, as it was...
...basically, it worked straight away. It didn't even need any adjustments.
The CD player hasn't missed a beat since, whenever I've used it over the past 2 years. It sometimes won't read my toughest copied disc, but it is as reliable a reader now as every other unit of this vintage on original disks and most copies, and way better than some later CD-rom type readers!
I'd have probably never understood how to identify and get at the fault without everyone else's explanation, so once again thanks. The sensor coil fix, coil-winding is a challenge, but it is DIY-do-able, and truly worth the effort with the Akai.
I'd wholeheartedly recommend the sound of the CD-93. It's genuinely, surprisingly good and definitely outshines most of its contemporaries in stock form, albeit they , are more well known, widely available and listened to! Looking back, it seems it was an expensive player in its time and so, when there is common but quirky, tricky fault, unsurprisingly they are quite rare and there are not so many around.
In short, I've found it very reliable and high-performing, since the repair.
Are you able to tell me which terminal is the start and of the coil and which direction the wire needs to be wound. I didn't make a note of this information when I removed the old wire from my one so I can't make that repair now even though I have the wire and a small coil winder.
Hi - not sure how best to explain from memory...one end needs to be fixed to the former /.body first (I think it was fixed on first at the rearward / transformer end, there are multiple passes required, obviously wound as one continuous length, winding in the same rotational direction. At the time, I made an aide-memoire as I unravelled the original, as I thought I might need to come back to it! I also took some close-ups before it was disassembled. The video should be the best guide - I hope this helps. All the best.
Attachments
I wound the coil for my one today but unfortunately it didn't work for me. The resistance is 2.9K with 7500 turns of 0.05mm wire so slightly lower than hoped.
The tray will now load smoothly without the wire link in place but the disc doesn't spin and nothing else happens once loaded.
If the sled is moved back manually it goes crazy and hammers back and force against the end stops so I now have another fault with this crazy CD player.
The tray will now load smoothly without the wire link in place but the disc doesn't spin and nothing else happens once loaded.
If the sled is moved back manually it goes crazy and hammers back and force against the end stops so I now have another fault with this crazy CD player.
I would definitely try connecting the coil ends the other way around, in case that is the fault...it may be difficult to see the correct direction from the video... Alternately, try rewinding the other direction to what you have.
Unless there is some other fault, it should come down to correct winding direction + correct connection terminals.
Hope it works out for you, soon.
All the best.
Unless there is some other fault, it should come down to correct winding direction + correct connection terminals.
Hope it works out for you, soon.
All the best.
In simple terms, I assume the control system is reacting to the induced voltage in the sensor coil - if it sees the wrong polarity or not the voltage spike it expects, then it will probably just accelerate, as you are seeing. I have seen this mad oscillating behaviour before, i.e. with the Pioneer PL-800 (linear-motor arm, turntable), when the feedback system is not registering (damaged lead).
I tried reversing the sense coil and it is now behaving itself. The disc spins up and loads as it should and the tray operates smoothly without any issues. That is the first time in 20 years it has been reliable without the wire link mod so I think my coil is good, just 180 degrees out. It was easy to fix with two small track cuts and a couple of wire links.
Unfortunately it has developed another problem while in storage. The left channel is silent and the right is distorted and low in level, on both headphones and rear panel analogue audio out. The digital optical out is working fine and sounds great, so I have more fault finding to do before it is 100% working.
Thanks again for the coil winding info which was invaluable even if I managed to get it wrong. It spurred me on to try again with the player as I had all but given up on it.
Unfortunately it has developed another problem while in storage. The left channel is silent and the right is distorted and low in level, on both headphones and rear panel analogue audio out. The digital optical out is working fine and sounds great, so I have more fault finding to do before it is 100% working.
Thanks again for the coil winding info which was invaluable even if I managed to get it wrong. It spurred me on to try again with the player as I had all but given up on it.
That's great news, another successful coil repair! 👍
Just as a thought, try cleaning (contact cleaner) the headphones socket and / or any volume potentiometer. The channel out could be a simple problem like that. Also hunt around for a possible degraded relay / contact...I'm glad you are now hearing it, despite the last niggles. Enjoy.
Just as a thought, try cleaning (contact cleaner) the headphones socket and / or any volume potentiometer. The channel out could be a simple problem like that. Also hunt around for a possible degraded relay / contact...I'm glad you are now hearing it, despite the last niggles. Enjoy.
It is a shame the analogue audio doesn't work as it was previously fine. It has gone from only one channel to nothing on both now. I sprayed some contact cleaner in the headphone volume pot but haven't looked at the headphone socket yet. I don't know if that cuts off the rear audio out but I would assume so.
I'm very happy the sense coil repair is a success because this has been a very long journey since the player first went wrong way back in 2008. It has languished in my cupboard for years at a time, only to be worked on every so often when I found some new enthusiasm. The DIY Audio forum has been an incredible help with this repair, without which I would never got this far, so a big thank you has to go to everyone who got involved.
I'm very happy the sense coil repair is a success because this has been a very long journey since the player first went wrong way back in 2008. It has languished in my cupboard for years at a time, only to be worked on every so often when I found some new enthusiasm. The DIY Audio forum has been an incredible help with this repair, without which I would never got this far, so a big thank you has to go to everyone who got involved.
Looking at the schematic, I don't think it's likely to be a headphone socket or volume pot causing the problem. This circuit is independent and fed from the analogue audio board, so it doesn't have any effect on the rear panel audio out.
The optical out is fed directly from the CXD1135 via some AND gates. The digital to analogue audio comes from the digital filter and a hex buffer before going to the analogue board, so potentially the fault could be on either board.
Time to get the scope out and see if I can trace the digital signal first. The player works happily with the analogue board removed, which makes it easier to probe the chips on the digital board first. I don't know how long this fault has been present because the last time I used it, I only hooked up the optical and didn't use it on headphones.
The optical out is fed directly from the CXD1135 via some AND gates. The digital to analogue audio comes from the digital filter and a hex buffer before going to the analogue board, so potentially the fault could be on either board.
Time to get the scope out and see if I can trace the digital signal first. The player works happily with the analogue board removed, which makes it easier to probe the chips on the digital board first. I don't know how long this fault has been present because the last time I used it, I only hooked up the optical and didn't use it on headphones.
Your suggestion of a degraded relay will be the first thing I check for tonight. There are two on the analogue audio board, which could potentially be causing a problem. I'll probe for the audio out of the PCM56Ps , which are before the relays and the output NE5532.
Problem solved... it was a dead 74HCU04 hex buffer on the output of the digital board. I pulled one from my Akai AM-65 amp DAC board to get it going until some new ones arrive. Analogue audio is restored once more and the CD-73 is now fully working.
Wow! I hadn't looked at this thread for maybe 2 years??
First of all, congratulations and 3 cheers to @andyb1712 (and the other DiyAudio members who tracked down the cause of this unusual fault).
No wonder these sense coils failed - Akai must have used the thinnest coil wire which exists.
I really should examine my Denon CD player (DCD-1500 II). It has a linear motor sled drive. I don't recall any Denon sense coils failing. But there was no standardization among these linear sled drives. Was Akai the only brand with high failure rates of sense coils?
The sense coil produces a voltage proportional to the velocity of the sled. The servo circuit requires this signal for stability. I doubt absolute position of the sled can be determined from this signal alone -- it's more likely the sense coil only detects sled velocity.
Could the sled drive circuit be modified to control sled velocity without requiring a separate sense coil?
Perhaps back EMF from the primary driving coil could be used?
Early 1980's Philips CDMx optical pickups contained a quasi-linear sled drive which rotated to move the optical pickup across the CD. There was a permanent magnet and a single driving coil. But no separate sense coil
Another workaround might be amplifying the signal provided by a sense coil rewound with heavier gauge wire and/or considerably fewer turns? A simple opamp circuit could do this.
-EB
First of all, congratulations and 3 cheers to @andyb1712 (and the other DiyAudio members who tracked down the cause of this unusual fault).
No wonder these sense coils failed - Akai must have used the thinnest coil wire which exists.
I really should examine my Denon CD player (DCD-1500 II). It has a linear motor sled drive. I don't recall any Denon sense coils failing. But there was no standardization among these linear sled drives. Was Akai the only brand with high failure rates of sense coils?
The sense coil produces a voltage proportional to the velocity of the sled. The servo circuit requires this signal for stability. I doubt absolute position of the sled can be determined from this signal alone -- it's more likely the sense coil only detects sled velocity.
Could the sled drive circuit be modified to control sled velocity without requiring a separate sense coil?
Perhaps back EMF from the primary driving coil could be used?
Early 1980's Philips CDMx optical pickups contained a quasi-linear sled drive which rotated to move the optical pickup across the CD. There was a permanent magnet and a single driving coil. But no separate sense coil
Another workaround might be amplifying the signal provided by a sense coil rewound with heavier gauge wire and/or considerably fewer turns? A simple opamp circuit could do this.
-EB