Myryad MC100 CD squeak

NickKUK

Member
2019-12-28 9:16 pm
I've owned my MC100 since new (IIRC about 1998) and it's been sat a while between uses (typically for parties with loud music) but now I'm using it with headphones about 1 foot away from the sitting position.
On playing a CD it has developed an annoying auditable squeak.

From my understand it uses a Sony CD engine so I suspect the transport is similar to many other CD players.

Before I get the screw drivers out to clean and lube - is this a DIY easy operation or am I going to destroy any alignment?
 
It is probably the focus error correction. This is caused by maladjustment of the focus gain control combined with the laser assembly having trouble acheiving focus.
There are no lubrication points although the spindle motor may require replacement if the bearing is dry.
If you have the correct equipment; Oscilloscope, (twin beam to measure the eye pattern of at least 50MHZ) service manual and Sony test disc it is not possible to set up without issues.
 

NickKUK

Member
2019-12-28 9:16 pm
I had chance to have a good look at it this morning.

Power supply board - all ok, all the power rails seem logical (ie 45V for the 30V output supplies,12V, 5V and 2.3V). I the main board seemed to power up with an ammeter across the blown fuse holder showing low current. Connected the front panel/control/display board and the CD player went straight from power into standby, then started up successfully - the KSS240A CD mechanism was left disconnected as I didn't want a laser in the eye. The system seems happy drawing 180-190mA (fused at 500mA).

So suspicion is pointing at the CD transport - that houses the CD engine and motor assemblies. I may be that the preciously reported 'squeek' is causing excessive current draw which would match the symptoms that it blew just as it was spinning up and seeking out a newly inserted disc.

I can get a laser assembly if it happens to be that but first I need to check if it's the spindle or another motor that is binding.
 
Last edited:

NickKUK

Member
2019-12-28 9:16 pm
Oil the motors
Leave overnight
Then check, by hand first

Oiled and leaving for a night, but I did try with a ammeter in the loop quickly. Peak of 550mA spotted. The fuse was 500mA.

The spindle motor didn't spin completely freely initially after letting go, but after a small drop worked in, it eased a little - enough to warrant a initial check but will leave overnight.

It's a CDM14 with a KSS240A but I can't find details on it's maximum current draw.
 

NickKUK

Member
2019-12-28 9:16 pm
I heard back from the folks that previous owned Myryad, it was sold to a Chinese owner in 2016 and no knowledge of staff remain :cry: - so no easy schematic. However I've pretty much suspect the mechanism and regulators. After all 550mA over the 500mA is obviously to fit the A1015Y 500mA transistor limits. That and the complementary BJT are sprinkled across the circuit board, so if it's going to go pop in an age related death there's still some options out there - replacing the CD engine, replacing the main board and DAC.. even converting it to something special - it would be a shame to waste the chassis, vacuum display etc. Perhaps a media CD and streamer.
 

MikePP

Member
2019-06-05 8:38 am
If you have a bench supply remove the mech and dis from any boards….then try running the spindle motor at 0.5v (D.C.) and slowly ramp it up to 1.0v , it should start to spin up.
Obviously with a disc in place and at start up from stationary it will draw a lot more current than at a steady speed, but it’s a good check if the motor has flat spots etc.
Then try the same with the sled motor , it might need a little more because it’s moving gears (no more than 1.5v though)

The laser current itself is written on the 3rd line down on the laser label (if it’s not fallen off already) , but it will only account for about 50mA more or less
If it says xx487 that means it was originally factory set to 48.7mA

If your squeak (squeal) is constant it will be servo’s over adjusted… it will be diffferent for each disc installed
 

NickKUK

Member
2019-12-28 9:16 pm
I notices something. Spot the issue:

8D1A9CE3-45D0-45AB-9E65-F766CFBBE6E6.jpeg

I was probing the power supply and the underside of the board lit up with mains arcing.

Turns out that the that a couple of joints weren’t even soldered or just tacked with the arcing it probably Leading to arcing! Only been that way for since 1996/97 but having not moved it much. So soldered that.