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Views: 4,038  ·  Replies: 21 
> Anyone good with electronic hardware?
kyonpalm
  Posted: Jul 25 2012, 01:12 PM


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Having some trouble with my beloved, but now-broken Kenwood turntable. Please help me diagnose and hopefully fix this excellent machine!

YOUTUBE ( http://www.youtube.com/watch?v=rRJaDC_scJ8 )
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Tuskano
Posted: Jul 26 2012, 12:02 AM


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Not too keen on the insides of turntables myself, but like the guy in the comment of your video said, it might be the stopper/switch. The motor seems to be fine from watching it.

It just needs whatever is telling it to stop/go to tell it that at the right time. I don't see any wires or sensors near the stopper/switch, but if there were any, I would think adjusting the switch to be longer or shorter to get it in range of the sensor would have done the trick.

Of course, this is a proffesional opinion coming from a mechanic who has no place really to be working with wires so I may be wrong. lol

If you ever really wanted to take the motor off (which I don't think you don't need to tongue.gif), I would recommend EzGrip which we use at work for tight or worn screws.

This post has been edited by Tuskano on Jul 26 2012, 12:02 AM
kyonpalm
  Posted: Jul 26 2012, 03:00 AM


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QUOTE (Tuskano @ 2 hours, 58 minutes ago)
I don't see any wires or sensors near the stopper/switch, but if there were any, I would think adjusting the switch to be longer or shorter to get it in range of the sensor would have done the trick.

You're right, there are none. I did think it was something to do with the stopper at first, but couldn't find anything that made that theory work... at least in my amateur opinion.

Thanks for the advice! If it is indeed something other than the motor, I have a feeling I won't be able to fix it myself, since I'm not yet good with circuitboards...
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Mazda ina Ford guy
Posted: Jul 28 2012, 02:39 PM


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I think Tuskano is on the right track, the stop switch (I suspect there is one) may be on the carriage the arm rides on (check the bottom), or at the end where it stops. Your 45 spacer may have tweaked it. And for God sake stop running the motor with the belt stoped, you'll put a "flat spot" on the belt. If you have run it more than a few minutes like that you should replace it, it is a delicate system, flat spots will throw off your arm speed as it progresses across the disc. Good luck hope you can figure it out. smile.gif

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THE_HONDA_CG2
Posted: Jul 28 2012, 02:50 PM


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We've talked about this prior to the creation of this thread. If you really want to get under those screws you'll have to use a vice grip or pliers to get at them since the screwdrivers that you've tried strip the screws in question. Vice grips are a manlier version of pliers so if you've tried my plier recommendation then my next course of action would be to step it up and use a vice grip. I wish you the best of luck with figuring this out! Hopefully we'll see the Kenwood up and running sometime soon!

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Möbius
Posted: Jul 28 2012, 04:17 PM


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Do not remove the motor, it is not your problem here. The problem is with the control of the motor, which I am not familiar with. It is most likely switches as there does not seem to be feedback circuit of any sort. I have no access to the schematics, but there has to be a way so it knows :

a ) Home position,
b ) Start position for a 33,
c ) Start position for a 45, and
d ) End position.

It looks like on power up it tries to make sure it is in home position ( so user can load a record ), but since it never confirms it, it keeps running.

And if you really want to remove the motor, it is most likely not a Phillips head, but a Pozidriv, which you most likely don't have any way. Also, it is most likely epoxied into place, so it will be really tough to remove.

Edit :

No, maybe I am being stupid....

The thing that looks like a fan under the circuit board, is probably what it uses to count revolutions. In that case, there is either only a zero switch, and then counts revs, in which case you have to find the switch... Or get ready for the worst...

It detects Home position by motor current. sad.gif

I am not prepared to make that call yet. Please post a pic of whatever is underneath that small circuit board next to the motor.



This post has been edited by Möbius on Jul 28 2012, 04:34 PM
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kyonpalm
  Posted: Jul 28 2012, 04:41 PM


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QUOTE (Mazda ina Ford guy @ 1 hour, 50 minutes ago)
And for God sake stop running the motor with the belt stoped, you'll put a "flat spot" on the belt.

Actually, after removing and replacing the belt, it moved with the wheel, so it won't be rubbing a flat spot anymore. cool.gif

QUOTE (Möbius @ 12 minutes, 38 seconds ago)
Do not remove the motor, it is not your problem here. The problem is with the control of the motor, which I am not familiar with. It is most likely switches as there does not seem to be feedback circuit of any sort. I have no access to the schematics, but there has to be a way so it knows :

a ) Home position,
b ) Start position for a 33,
c ) Start position for a 45, and
d ) End position.

It looks like on power up it tries to make sure it is in home position ( so user can load a record ), but since it never confirms it, it keeps running.

Brilliant deduction, Möbius! I had this confirmed to me by a master of electronics just yesterday. This is what he had to say:

QUOTE (Davide Gatti)
Ok saw the video. When I can get the schematic I can be more precise. So at the moment I can suppose that a 45 plastic inside the mechanic has blocked the arm mechanism and the motor tie down more current and damage the regulator. As I can see propably is a little Integrate Circuit with three legs fitted on a small board behind the motor.

Another possibility is that the encoder opto is not alligned properly.
Near the motor you can see a plastic detail that turn with three wings

Theee or more I can't see properly on video
There are a sensor normally similar to U letter where the wings pass through
If this sensor was misalligned the logic circuit do not detect the motor rotation
And can't understand when it is stopped
Normally the sensor have 4 wires
Check if it is all properly connected


Since he's on vacation in Greece at the moment, he cannot give me a definite set of instructions until he's back home and can find the schematics. Looks like a repair might be possible!

In the meantime, I've gotten another turntable. This one I'm really excited about, since it is one of my favorite brands - a Technics SL-Q200:

user posted image
Image size reduced, original size: 900 x 600. Click here to view the image in its original dimension.


That's not my pic, it's the eBay seller's. Should arrive here early the week after next.

EDIT:
To Mobius' edit - I will try to dismantle it and get better pics tonight.

This post has been edited by kyonpalm on Jul 28 2012, 04:42 PM
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Möbius
Posted: Jul 28 2012, 04:45 PM


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QUOTE (kyonpalm @ 3 minutes, 27 seconds ago)
Actually, after removing and replacing the belt, it moved with the wheel, so it won't be rubbing a flat spot anymore. cool.gif


Brilliant deduction, Möbius! I had this confirmed to me by a master of electronics just yesterday. This is what he had to say:

QUOTE (Davide Gatti)
Ok saw the video. When I can get the schematic I can be more precise. So at the moment I can suppose that a 45 plastic inside the mechanic has blocked the arm mechanism and the motor tie down more current and damage the regulator. As I can see propably is a little Integrate Circuit with three legs fitted on a small board behind the motor.

Another possibility is that the encoder opto is not alligned properly.
Near the motor you can see a plastic detail that turn with three wings

Theee or more I can't see properly on video
There are a sensor normally similar to U letter where the wings pass through
If this sensor was misalligned the logic circuit do not detect the motor rotation
And can't understand when it is stopped
Normally the sensor have 4 wires
Check if it is all properly connected


Since he's on vacation in Greece at the moment, he cannot give me a definite set of instructions until he's back home and can find the schematics. Looks like a repair might be possible!

In the meantime, I've gotten another turntable. This one I'm really excited about, since it is one of my favorite brands - a Technics SL-Q200:

http://i.minus.com/j6LDFGPqZXqLL.jpg

That's not my pic, it's the eBay seller's. Should arrive here early the week after next.

EDIT:
To Mobius' edit - I will try to dismantle it and get better pics tonight.

I ninja'd you.

Check my edit above. smile.gif

The opto encoder he is talking of is the black fan thingie I was posting about.

If you post a pic of what is under that circuit board, the black fan thingie and whatever else is under there, I can probably confirm.
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Mazda ina Ford guy
Posted: Jul 28 2012, 05:35 PM


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Looks like you've covered your bases, mad props for spinning actual vinyl! smile.gif

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Möbius
Posted: Jul 28 2012, 06:08 PM


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Come on, get the pic, this might be an easy fix, unless it detects by motor current.
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kyonpalm
  Posted: Jul 29 2012, 04:02 AM


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QUOTE (Möbius @ 8 hours, 51 minutes ago)
Come on, get the pic, this might be an easy fix, unless it detects by motor current.

Sorry, I just got around to it now. I wanted to get video as well. Here are some pictures of the cluster of parts in question...

user posted image
Image size reduced, original size: 4000 x 3000. Click here to view the image in its original dimension.


user posted image
Image size reduced, original size: 4000 x 3000. Click here to view the image in its original dimension.


user posted image
Image size reduced, original size: 4000 x 3000. Click here to view the image in its original dimension.


user posted image
Image size reduced, original size: 4000 x 3000. Click here to view the image in its original dimension.


user posted image
Image size reduced, original size: 4000 x 3000. Click here to view the image in its original dimension.


user posted image
Image size reduced, original size: 4000 x 3000. Click here to view the image in its original dimension.


That black piece connected to the circuit board in the last couple pictures is part of the opto encoder (the fan-like thing spins in the opening.)

Here is a picture of the underside of the tonearm unit, as requested:

user posted image
Image size reduced, original size: 4000 x 3000. Click here to view the image in its original dimension.


There doesn't seem to be anything in it that would directly indicate when the unit has reached its end point. Here is the video...

YOUTUBE ( https://www.youtube.com/watch?v=Hmk3UJAvBkQ )


QUOTE (Mazda ina Ford guy @ 9 hours, 24 minutes ago)
Looks like you've covered your bases, mad props for spinning actual vinyl! smile.gif

Thanks. I'm a big fan of the format and have been collecting records for a couple years now. For the past year, I've pretty much ignored buying CDs entirely. The satisfaction that comes with the superior packaging and playing experience is wonderful and you don't get that with any other format.
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HorizontalMitsubishi
Posted: Jul 29 2012, 09:21 AM


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What I'd try is to put the light sensor back into place, and unloop the drive cable off of the white spool and turn it on and see if it's able to count enough rotation to find it's "home" position then put it all back together and see if it runs.
Möbius
Posted: Jul 29 2012, 04:41 PM


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QUOTE (HorizontalMitsubishi @ 7 hours, 20 minutes ago)
What I'd try is to put the light sensor back into place, and unloop the drive cable off of the white spool and turn it on and see if it's able to count enough rotation to find it's "home" position then put it all back together and see if it runs.

Good suggestion, but at the same time I would be surprised if the unit references everything off of that.

user posted image

What's that in the yellow circle?
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kyonpalm
  Posted: Jul 29 2012, 04:48 PM


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QUOTE (Möbius @ 6 minutes, 36 seconds ago)
What's that in the yellow circle?

Not 100% sure, since I couldn't lift the arm unit out completely. To do that, I would have to uncoil the drive wire like HorizontalMitsubishi said. I'll do that next chance I get, but that might not be for a little bit. Bear with me, I'll have pics of that up as soon as I can get them this week.
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Möbius
Posted: Jul 29 2012, 04:49 PM


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QUOTE (kyonpalm @ 1 minute, 15 seconds ago)
Not 100% sure, since I couldn't lift the arm unit out completely. To do that, I would have to uncoil the drive wire like HorizontalMitsubishi said. I'll do that next chance I get, but that might not be for a little bit. Bear with me, I'll have pics of that up as soon as I can get them this week.

Just asking since it is on the bottom of the unit and has two wires connected to it. Might be something to pick up the home position, hard to see in the pic.
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HorizontalMitsubishi
Posted: Jul 29 2012, 09:10 PM


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I didn't notice that previously, but I think that might be the sensor that looks for the home position.
kyonpalm
  Posted: Aug 1 2012, 07:58 AM


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Okay, the whole thing has been fixed. Big thanks to HorizontalMitsubishi for making me think to look under the tonearm unit and also thanks to Möbius for working the last kinks in the system out with me. cool.gif

YOUTUBE ( http://www.youtube.com/watch?v=3B01Q1mexO8 )
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Wanderer
Posted: Aug 1 2012, 02:50 PM


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Doesn't it feel good when you can fix something yourself that you originally didn't think you could?

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kyonpalm
  Posted: Aug 1 2012, 03:11 PM


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QUOTE (ATRUM_Neto @ 20 minutes, 25 seconds ago)
Doesn't it feel good when you can fix something yourself that you originally didn't think you could?

user posted image

Though like I said, I have Möbius and HorizontalMitsubishi to thank for helping point me in the right direction.
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Möbius
Posted: Aug 1 2012, 05:01 PM


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Actually it was Mazda in a Ford Guy who asked to see the underside... tongue.gif
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kyonpalm
  Posted: Aug 1 2012, 05:06 PM


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QUOTE (Möbius @ 4 minutes, 14 seconds ago)
Actually it was Mazda in a Ford Guy who asked to see the underside... tongue.gif

Oh shoot! My apologies, Mazda in a Ford Guy! pinch2.gif
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Mazda ina Ford guy
Posted: Aug 2 2012, 05:30 PM


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No offence taken! Glad to see you got it working. smile.gif

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