What does the muting relay circuit look like?
The best line-level muting circuits ground out the audio signals to mute them. This way the audio signals don't need to pass through the relay contacts on their way to the output jacks. The relay contacts only play a role during muting.
The original wire in the sense coil was incredibly thin and extremely fragile. When I first took it apart my heart sank as I thought, how will I ever rewind this. The replacement wire I used is at least 25% thicker and has resulted in a physically larger coil, no doubt with less turns and lower overall resistance. It clearly isn't significantly different enough to affect functionality though. I have been using it a lot over the last week or so and it hasn't missed a beat yet.
A considerable amount of time was spent focused on fault finding the tray control system, when it was really the MCU firmware telling us there was a fault elsewhere. It's a shame there was nothing in the Akai service manual about this as it is clearly by design to prevent a disc being loaded when a fault is detected.
Repairing the coil close to original spec isn't impossible but it took me about 4 hours to do it, carefully moving the coil winder to layer the wire and build it up as evenly as possible. It's not something I'd want to do again but hopefully I won't have to. I just hope the KSS-151A has plenty of life left but it should be ok having been mostly unused for the last 17 years.
I nearly threw in the towel this player on more than one occasion but it shows the power of the internet when like minded individuals come together. It was truly an international effort, for which I am very grateful. 🙂
A considerable amount of time was spent focused on fault finding the tray control system, when it was really the MCU firmware telling us there was a fault elsewhere. It's a shame there was nothing in the Akai service manual about this as it is clearly by design to prevent a disc being loaded when a fault is detected.
Repairing the coil close to original spec isn't impossible but it took me about 4 hours to do it, carefully moving the coil winder to layer the wire and build it up as evenly as possible. It's not something I'd want to do again but hopefully I won't have to. I just hope the KSS-151A has plenty of life left but it should be ok having been mostly unused for the last 17 years.
I nearly threw in the towel this player on more than one occasion but it shows the power of the internet when like minded individuals come together. It was truly an international effort, for which I am very grateful. 🙂
From memory I don't think the audio signals pass through the relay contacts. They are just used to used to control the muting electronically. They are only on the analogue audio board which I don't tend to use. I prefer to feed the digital optical output to my Pioneer LX86 and let that handle the D to A.
I have a similar problem with sled motor on VRDS mech and KSS 151a. The laser stops half way and the head attempts to search for TOC which results in " no disc " message " When I push the laser under the clamping mechanism the TOC is read and there is no problem with a playback. Sometimes it works a day without glitch and next day it starts doing the same. Machine is a real headache to work on
There are a couple of these Akai players currently for sale in Canada, which I enquired about buying. Unfortunately the shipping cost to the UK was very high and in the interests of 'domestic harmony' I decided not to proceed with spending nearly $500 on two more broken CD players having only just repaired my current one.
The only shame about this is they will probably be bought for parts, in particular the rare laser, meaning they will never be restored.
https://www.canuckaudiomart.com/details/650210134-akai-cd-73/
The only shame about this is they will probably be bought for parts, in particular the rare laser, meaning they will never be restored.
https://www.canuckaudiomart.com/details/650210134-akai-cd-73/
Maybe it's worth looking at the sled sense coil resistance? The original Akai one was 3.1k when working but my failing one went to 44k before going open circuit. The repaired one measures just over 2.9k, which is fortunately close enough to work.
Thank you Andy. Machine in question is Spectral SDR 3000 with servo board based on undisclosed Teac unit. You have to pretty much take the whole thing apart to get to that board. The only thing which motivates me to futz with that clunker is the fact that it is arguably the best sounding CD transport ever produced.
Maybe you can access the sense coil in the same way as the Akai? To do that you just open the CD tray and you can put probes on the coil terminals directly on the top of the laser assembly. If it has the same laser as the Akai, this should be the same and wouldn't require any disassembly. Removing and repairing the failing coil does however mean removing the whole CD mechanism and taking it apart.
