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Help with a broken Akai cd-93

L

LouiePollard

New Member
Howdy,
I got my dads old CD player out of the loft to add to my new system. We turned it on and the cd tray didn’t open, but we could hear whirring inside.
We opened it up and the belts had disintegrated, so we replaced them and it all worked fine. Now when it closes, one of the switches just wobbles back and forth and then the tray just opens again.
Any ideas?
Here’s a video of the issue in more detail
 
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cpt_paranoia said:
Clean the switch contacts?

Try shorting the contacts during that jittering phase; see if it starts playing.
Click to expand...
If I push the contacts together before it reaches them, it just jitters wherever it is on the travel.
If I do it before the disc tray finishes moving then the other part doesn’t move at all.
Tried cleaning with some contact cleaner but not sure if that’s the issue
 
This player, and the related CD-73 are notorious for this issue. It is apparently due to some sort of sensor and logic/cpu failure for which no proper fix is available due to lack of replacemment parts. There was a lengthy thread on it here somewhere, will see if I can find it and link it in this thread if I do.

Edit to add: I searched extensively and couldn't find the thread I was thinking of. Now I'm guessing it may have been on another audio forum I ran across while looking for CD player repair info on another model. At any rate, it was something I read several months ago, and I don't know where it was now.

I do recall the thread discussed it being an issue with a failed logic pin on one of the IC's that read a sensor that governed the drawer closure action. Since the IC was an MCU with custom firmware, there was no source for a replacement. The consensus was the only way to fix it would be to custom brew a bit of electronics to that would bypass the original drawer sensing and control, but it was unclear if that would even work, since the MCU in question would still be looking for a certain logic state at drawer closed, and probably wouldn't spin the disc up without that logic signal present. All in all, it struck me as a stupidly and unnecessarily complex design that doomed these players to being boat anchors, once the sensor and MCU failed. Unfortunately, that appears to be the fate of nearly all of them.
 
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The discussion you mentioned is on the DIY Audio forum under CD-93. I spent a very long time getting to the bottom of this problem and with help from many others finally repaired my player.

Akai CD-73 / KSS-151A Sense Coil

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...
www.diyaudio.com www.diyaudio.com

The problem is caused by the laser sled sense coil failing. The tray oscillating is a warning by the MCU of a problem and refusing to load the disc because of it.

The only way to fix this is to remove the coil from the mechanism and rewind the coil. This is no easy task. I fixed it with 7500 turns of 0.05mm enamelled copper wire wound on the original coil former after removing the old wire.
 
Excellent work there. I read the updated thread DIYAudio, and am duly impressed you were able to restore this player to proper operation. I take it the break in the original coil was a good number of turns in from the end?
 
Thank you... it was a long road to the repair and not an easy task to finish. The sense coil original wire was so fragile that it just kept breaking every time I tried to unwind it, so I never found the break.

I weighed the original wire to try and figure out what I needed and worked out 0.04mm was probably the optimal size. I went for 0.05mm in the end.

I bought a cheap hand coil winding machine for £30 and the wire was £12, so not too expensive. It took me about 4 hours to wind it using a magnifier and somehow I managed to do it without breaking the wire once.

Others with working units measured the coil at 3.1Kohm and my repaired one was 2.9Kohm, which was close enough to get it working again.
 
I lusted after one of these players for a few years while I had the matching integrated amp, and tuner in my system, but I avoided one because of this issue, nice to know it's actually repairable with tenacity.
 
I picked my CD-73 up cheap when the MP3 revolution hit but it didn't last long before it failed. I had some earlier Akai components, an AM-U61 amp from 1983 with matching tuner, which I paired it with and these are still going strong.

The CD laser sense coil clearly had a design flaw for so many of them to be affected by it. I used slightly thicker wire to rewind my one, which I hope will make it more reliable. It wasn't an easy task but a small hand operated coil winding machine bought on eBay helped a lot.

I guess most have developed this fault by now and have been scrapped. How many are repaired remains to be seen but it's not impossible to do.
 
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