Is it possible to repair nakamichi cd pickup "home" laser? - diyAudio
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Old 25th April 2008, 05:18 AM   #1
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Default Is it possible to repair nakamichi cd pickup "home" laser?

I have a Nakamichi MB-100.

Every time the unit is powered up, turned on, or CD changed, The pickup laser goes through a sequence where the lead screw drags the pickup towards the drive motor until it collides with a micro-switch, telling the cd player it has reached the "home" position.

The cd player then continues its' final startup activities before playing the CD.

If the switch is not met, then the lead screw will turn and turn and turn until the player times out and posts E-MECHA.

--------------------------

My problem is the switch requires just too much force for the pickup to activate. The pin that holds the pickup to the lead screw will skip over the lead screw groove rather than depress the switch all the way.

It is so close to being OK that if the unit is bumped, say via speed bump or by a gentle rapping with an open palm on the dashboard, the switch will depress more via vibration and the unit will continue.

One time out of 30 or so it will actually work without human intervention.

--------------------------------

I'd like to know if it is possible to service the switch or if it has to be replaced. The first thing I tried was some oil/grease via fine syringe on the switch shaft to try to loosen it up a little. This did not affect performance (I used krytox as the oil in a torrlube syringe)

If it has to be replaced I'd like to know if I have options to source a part, and the experience of some Nakamichi service providers that whether a part in this particular location is replaced via the part itself or replaced with an entire assembly. Say, the entire platform that drives and reads the CD.

Thanks guys,

Steven
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Old 25th April 2008, 09:16 AM   #2
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Lead screw assemblies wear out. Not so much the screw shaft, but the ball thread assembly it feeds through. When this happens you get a situation where the pickup assembly will not hold position, and it will back off rather then actuate a position sensor.

Lead screw motors also wear out, along with spindle motors, and then they lack the drive momentum to complete their task such as simple switch actuation and rotational speed of the disk.

Then theres the possibility that the sensor has stiffened up with use and age and is the main culprit. Becoming erratic and unreliable in its operation.

Using Torr-lube or any synthetic PTFE high vacuum rated lubricant will most probably only cause more problems. Sensors rarely need lubrication to operate properly, and if the do they will become unreliable in the long run due to contact contamination or mechanical instability < PTFE based lubricants are non conductive by there chemical makeup>. Lead screws require specific lubricants as prescribed by the assembly maker.

As with many electro-mechanical failures, the symptom may not be the problem. After fixing a few symptoms in my time, I have learned to look abit further.

Your selection of lubricant although expensive and exotic, is probably not in your best interests. I am familiar with these lubricants and your applicator as I have also had my head inside a chamber or two in my life.

Getting parts from Nak is probably the next worse issue you will have. I mentioned a few of the failure modes I have seen over the years on CD mechanism's so as to enlighten you to what I know and have experienced.

CD mechanisms are very sophisticated mechanically speaking, and only matched by the electronics supporting them. But after enough time they all look alike after a while, and they all have similar failings.

Depending on this units age, it might just be time for a new pickup and lead screw assembly. It happens everyday, my good friend stocks them by the dozens. Unfortunately he services car head units, not home units, hence my kind words about Nak parts availability.
But a call to a Nak service center might clear the question about weather a new part can be had, and at what cost.

Nothing lasts forever, and greasing a squeaky assembly might be the answer in some cases. In your case I feel it is not. I would call to find parts support from Nak, then consider the cost to return ratio involved.
Plus you can also ask about their flat rates of repair. It might just be worthwhile to allow them the burden of making this right by you, after all "Time is Money".

Hope this helps some....
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Old 25th April 2008, 10:11 AM   #3
Mooly is offline Mooly  United Kingdom
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Hi, agree with 1moreamp about lead screw but if it's OK try this. Can you remove switch ? Leave it to soak a few hours in WD40 (you have that over there ?). and try and squirt some in the switch under pressure. Keep working the switch while immersed.
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Old 25th April 2008, 04:26 PM   #4
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thanks for the initial advice guys.

Compared to an identical car cd player (MB-X) I admit that the spring clip that holds the laser pickup to the lead screw "seems" qualitatively looser than my MB-X.

I dont have a clue how I can tighten this.

I'm still hoping there is a way to correct as opposed to replace the parts.

Anyone ever have their hands wrist deep into an MB-X, MB-VI, MB-100, MB-75, or MB-70?
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Old 25th April 2008, 04:38 PM   #5
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You have a e-mail of my local shop buddies that can lend a hand. Good luck, Nak and parts availability are the problem, always has been.
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Old 26th April 2008, 12:14 AM   #6
MadMutt is offline MadMutt  Australia
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mb100 (and mb70/75/etc) - resolder 'cn107'.
That cures a LOT of 'e-mecha' errors.

Nak parts, go directly to nak singapore (think thats right).

EDIT, White rabbit, Yes, I have.
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Old 27th April 2008, 03:57 PM   #7
Clipped is offline Clipped  Thailand
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micro switches are used in the doors of some microwave ovens for safety precautions...usually 3-4 of them are located throughout...maybe you can locate one from a dead wave.
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Old 27th April 2008, 05:07 PM   #8
Mooly is offline Mooly  United Kingdom
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Think the switch might be bigger than the pickup.
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Old 28th April 2008, 02:08 AM   #9
Clipped is offline Clipped  Thailand
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the ones ive seen are the size of the switches used inside of the remote control of a car alarm.

smaller than the head of a match.
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Old 26th May 2008, 04:49 PM   #10
marko is offline marko  United Kingdom
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Quote:
Originally posted by MadMutt
mb100 (and mb70/75/etc) - resolder 'cn107'.
That cures a LOT of 'e-mecha' errors.

i got an mb100 with the same e mecha error, maybe i should give it a shot! would be a shame not to get this beauty up and running






EDIT- where is cn107 located inside the unit? i have mine in bits now and everything looks ok and can't see anything obvious broken!
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