Is it possible to repair nakamichi cd pickup "home" laser?

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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.

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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.

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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
 
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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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.
 
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?
 
MadMutt said:
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!
 
(EDIT - won't look broken, bad solder joints)


cn107 is a small white flat 'ribbon' connector.
On the car versions it'll be on the front edge of the main board.
It is only accesible by removing the board.

You will possibly find that all of the ribbon connectors respond well to re-soldering.

Resoldering these will only be possible if you are very experienced with small surface mount/magnifier type work.

Best method is with a reflow pencil.

Other 'e-mecha' errors are mechanical.
I'd list them but there are just so many it ain't funny.
Sufice to say, a tiny smear of fine grease is used in many of them.

Others are back to basics mech alignments. (normally only an issue for the changer versions).
 
right, if i press the reset button the transport goes through a series of manouevers, it does each of the 6 disc trays but about half way though it just stops and then the e-mecha comes up..

any ideas? i have located cn107, it does look ok but a re-solder wouldn't harm i guess and i have nothing to loose!
 
marko said:
right, if i press the reset button the transport goes through a series of manouevers, it does each of the 6 disc trays but about half way though it just stops and then the e-mecha comes up..

any ideas? i have located cn107, it does look ok but a re-solder wouldn't harm i guess and i have nothing to loose!


I've repaired ~100x mb75/mb100 's (and their variants).

What I said above stands.
You won't/can't see the joint failure. Trust me, It's there.
The mechanical faults are detailed in a 25 page tech doc from Nak.
This doc does NOT cover all of the known issues/fixes.
I know of about another 5 fixes on top of Nak's......

cn107 will fix about 70% of units with 'e-mecha'...
 
marko said:
i will go away and redo cn107 then.... i take it the easiest way would be to remove the old solder and apply fresh?


If thats what you find easiest.

Really being a wave soldered board there's close to nil solder on there anyway.
So just going 'over the top' isn't an issue.

Desoldering will help clean the tracks and pins and make it easier to get a better job.
BUT, the tracks are very sensitive to heat and lift easily.

Could also consider solder paste and reflow the joints.

Oh, and the connector plastic doesn't like to much heat either :rolleyes:

Really it's a bugger of thing.

Best of luck :smash:
 
I do it with a hakko station (fine tip), 5x diopter glass, and 0.3mm solder.

Need to find a place that will run a hot air pencil (reflow) over it for you.

Some sort of electronics repairer might be able to help.

Maybe a place that does game console mods ?
They should be well versed in minature soldering..
 
Please don't use WD-40. That will cause more problems. I use'd to do the factory service for Canada. CN701 is the problem, then you have to reset the mech. The solder they used is too soft and pulls off easy so be careful. I still have some parts for these units (MB-70/75/100) and some for the CD-700 series if your looking for any. I've only had to replace one laser pickup assy.

Martin
 
This is only one part of the alignment, but its the most important one.

The rest should be right, unless someones 'played' with them.
Most of the others have an associated mod needed too.
(file here, drill there, replace modded part x)

I found 95% of the ones I've done needed only cn107, and this 'stack' mech to be realigned.

Watch those little white 'seats' (F01) on the four legs. (away from the mech plate) They have a small spring in them, and go 'TING' easily.

You will kill yourself if (when) one 'dissappears'........
 

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