View Full Version : Fisher MT-6225 platter grinding


Hopewrecker
03-18-2012, 02:13 PM
Hello, I'm hoping the good people of AK can help me. I've lurked a little and tried searching for answers but thought I would go ahead and ask for help. Hopefully someone here has this turntable or has worked on one before. I got this Fisher mt-6225 for free and it was pretty gunked up from being in storage for a while. I cleaned it up and tried to get it running but the magnetic strip under the platter rubs against the "sensor"(sorry, don't know what they're called)strips as it goes around. It's enough to throw off the speed, make an ugly grinding noise, and I just want to see if there's any way to fix this. Some way of sanding this magnetic strip down a little. I'm also wondering if there is any way to actually adjust the sensor part so it's just a hair farther away. Doesn't look like it, but maybe?
Any help would be greatly appreciated, thanks in advance!

Balifly
03-18-2012, 02:39 PM
Welcome to the AK turn table forum. :music:

Do not sand or alter the magnetic strip in any way. :no:

Post some pictures of the trouble area if you can and go from there.

boreas
03-18-2012, 02:50 PM
Looks like quite a decent turntable, well worth the effort to try and sort out.

Try to find out why it's rubbing and exactly where. Actually, if indeed the platter is rubbing in the vicinity of the array of coils, I'd suspect that the platter is riding too low and not too far to one side. See if you can see any rub marks on the platter or on the turntable. If there are any, let us know.

I've seen Fishers (made by C.E.C.) and other tables that have plastic spindle housings. Sometimes, after several decades, the plastic deteriorates and cracks around the base of the housing. That allows the platter to drop and then rub against the first thing it comes in contact with. Also some turntables have a plastic thrust plate inside the spindle housing. They often degrade for the same reasons (exposure to oil and time). When that happens the spindle3 drops down inside the well and, again, the platter drops.

John

Hopewrecker
03-18-2012, 03:28 PM
There are definite rub marks on the magnetic strip and the coils. I'll take some photos pretty soon here. The magnet on the platter has very faint cracks on it, nothing that actually sticks out or makes a snag. I pulled apart as much as I could to try and just clear out any dust or debris. Now for the bad news...I did sand it lightly with fine grit. In my research I came across something that said that was alright. If I screwed up it for good I'll feel terrible! But after putting it back together, the grinding has gone down to more of a scraping and it still doesn't keep speed. It fluctuates every time it goes around that spot.
I appreciate the feedback already. You guys are great. If anyone can help me save this beauty it's you!

boreas
03-18-2012, 03:36 PM
So, it's rubbing at one spot once per revolution?

Do you see any wobble in the platter as it rotates?

Have you checked the spindle and spindle bearing?

John

Hopewrecker
03-18-2012, 04:08 PM
So, it's rubbing at one spot once per revolution?

Do you see any wobble in the platter as it rotates?

Have you checked the spindle and spindle bearing?

John

It's rubbing in two spots every revolution. I don't see any wobble at all as it rotates. I pulled out the spindle and examined it. Nothing is broken or cracked. Just maybe old grease in there. Oh, and I sanded it before Balifly said that was a no-no. I should have come here first. :/

Hopewrecker
03-18-2012, 04:22 PM
Here's a couple photos, don't know if they'll help at all.
http://i39.tinypic.com/14u9pvt.jpg
http://i44.tinypic.com/vmu29u.jpg

boreas
03-18-2012, 04:36 PM
Here's a couple photos, don't know if they'll help at all.


Not much. The auto-focus locked in on the wrong areas, especially on the platter. In any event, seeing rub marks isn't as helpful as being able to lay hands on the table itself.

Okay, so the spindle's okay, right? What about the spindle bearing and the entire rest of the spindle assembly? Also, hile you're in there it wouldn't hurt to clean all the old grease out of there and re-lubricate the spindle. Also, wiggle the spindle while its in place and check for slop.

Okay?

Now try this. Take the bottom off the turntable (or whatever you need to do to get inside the thing) and look for the screws/bolts that are holding that array of coils in place. Loosen them and see if you can shift the entire assembly away from the platter. If you can that should solve the rubbing problem.

If you do solve the problem but the speed is still erratic it might be the result of your sanding but it's more likely to be dirt in the speed controls. We can get you through that as well.

John

Hopewrecker
03-18-2012, 04:53 PM
I took the spindle out and cleaned it and put some new oil on it and now the platter won't even go back on, it's so close to the coils. There's no wiggle room to the spindle and I put it back the same way I took it apart. It's just a spindle encased in a little shaft...is this right?

I took the bottom off yesterday and there doesn't seem to be anyway that I could get to that coil housing. (There must be, I'm sure, I just didn't see it).

Hopewrecker
03-18-2012, 05:03 PM
Here's all there is to the spindle.

http://i43.tinypic.com/nup6w.jpg

boreas
03-18-2012, 05:07 PM
I took the spindle out and cleaned it and put some new oil on it and now the platter won't even go back on, it's so close to the coils.

That doesn't sound right. Are you sure that the spindle has bottomed out in the bearing well? Often (nearly always) the spindle is at suck close tolerance to the bearing that the oil you added to the bottom takes a long time to seep past the spindle and allow the spindle to go all the way to the bottom of the well.

There's no wiggle room to the spindle and I put it back the same way I took it apart. It's just a spindle encased in a little shaft...is this right?

No wiggling is good. Yes, the spindle does ride inside a cylindrical housing with a machined bearing surface inside (if it's a metal one). There's often a small ball bearing in the bottom of the well so that the base of the spindle isn't in full contact with the bottom. When there is a ball bearing there's typically a small indentation in the bottom of the spindle for the ball to seat itself in. Sometimes the ball bearing goes missing. That allows the platter to drop down farther than it should. That could be your problem.

I took the bottom off yesterday and there doesn't seem to be anyway that I could get to that coil housing. (There must be, I'm sure, I just didn't see it).

Okay, in your photo of the coils see that screw head just visible in the photo to the right of the coils? Is there another screw in the corresponding position on the left end of the assembly? Those could be what's holding the assembly in place.

John

boreas
03-18-2012, 05:14 PM
Okay, in your photo of the coils see that screw head just visible in the photo to the right of the coils? Is there another screw in the corresponding position on the left end of the assembly? Those could be what's holding the assembly in place.

John

I just looked at a photo online and I doubt that those two screws hold the motor. I think those two screws and the other two similar screws on top probably hold the sub-chassis to the base.

Could you take the bottom off again and give us a photo of the insides?

John

Hopewrecker
03-18-2012, 05:18 PM
First off, I want to thank you so much for your continued replies and suggestions. Your help is keeping me from completely giving up on the whole thing..ha. There was no ball bearing in the spindle housing. Don't know if there ever was one.

I'm going to loosen the screws you mentioned in the photo and see what's what.

Hopewrecker
03-18-2012, 05:18 PM
I just looked at a photo online and I doubt that those two screws hold the motor. I think those two screws and the other two similar screws on top probably hold the sub-chassis to the base.

Could you take the bottom off again and give us a photo of the insides?

John


Oops, just read this. Yeah, I will take that photo now.

Hopewrecker
03-18-2012, 05:29 PM
This is directly underneath that coil housing. It's actually the bottom ends of the bolts that most likely hold it in place, the top end being under the housing.
http://i44.tinypic.com/2akk8wo.jpg

http://i41.tinypic.com/6yf4zn.jpg

Pio1980
03-18-2012, 05:31 PM
First off, I want to thank you so much for your continued replies and suggestions. Your help is keeping me from completely giving up on the whole thing..ha. There was no ball bearing in the spindle housing. Don't know if there ever was one.

I'm going to loosen the screws you mentioned in the photo and see what's what.

Spindle end is pointed, there wasn't a ball. The thrust plate may need attention if cracked or dimpled plastic.

illini
03-18-2012, 05:33 PM
http://www.audiokarma.org/forums/showthread.php?t=406818

FWIW, I had a similar problem and the root cause was in the spindle/motor. The platter speed reader "tapehead" was not hitting anything, though.

Pio1980
03-18-2012, 05:37 PM
A straight-on top pic of the coil assemblies could be helpful.

Hopewrecker
03-18-2012, 06:09 PM
A straight-on top pic of the coil assemblies could be helpful.

Here you go:
http://i42.tinypic.com/30mmjiw.jpg

and another angle
http://i39.tinypic.com/30jh28h.jpg

Hopewrecker
03-18-2012, 06:11 PM
Spindle end is pointed, there wasn't a ball. The thrust plate may need attention if cracked or dimpled plastic.

There doesn't appear to be anything wrong with it. I mean, as far as I can tell, it looks okay.

boreas
03-18-2012, 06:21 PM
I think these are the three screws that hold the motor assembly in place.

John

Hopewrecker
03-18-2012, 06:23 PM
They are, but not the slotted end. Those are the ends with the bolts.

Pio1980
03-18-2012, 06:30 PM
The stator coil assembly may have shifted inward somehow, look carefully for any sign. I suspect the screws may be loose.

petehall347
03-18-2012, 06:31 PM
i think the motor is skew whiff are there any rubber mounts that have deteriorated ?
failing that a shim may be missing

boreas
03-18-2012, 06:33 PM
The stator coil assembly may have shifted inward somehow, look carefully for any sign. I suspect the screws may be loose.

Right. That's what I've been trying to get at.

John

Hopewrecker
03-18-2012, 06:34 PM
The stator coil assembly may have shifted inward somehow, look carefully for any sign. I suspect the screws may be loose.

It looks level and actually is dead solid. The housing and the coils themselves don't move at all.

boreas
03-18-2012, 06:36 PM
i think the motor is skew whiff are there any rubber mounts that have deteriorated ?
failing that a shim may be missing

It's rigidly mounted but, yes, I think the stator (motor) has to have moved. I can't really think of another explanation that hasn't already been ruled out.

John

jleon92f
03-18-2012, 06:52 PM
Here you go:
http://i42.tinypic.com/30mmjiw.jpg

and another angle
http://i39.tinypic.com/30jh28h.jpg

Hi, measure the distance between the coil surface and the spindle, should be equal all around.

John.:music:

Hopewrecker
03-18-2012, 07:01 PM
Hi, measure the distance between the coil surface and the spindle, should be equal all around.

John.:music:

Just measured it, it's equal.

boreas
03-18-2012, 07:07 PM
Basically, what those C.E.C. direct drives use is a belt drive platter with a strip of refrigerator magnet wrapped around the belt race. ;) The magnetic strip isn't separating from the platter anywhere is it?:dunno: I didn't ask this before because I figured the OP would have seen this while sanding the strip.

John

petehall347
03-18-2012, 07:27 PM
i am wondering if the plastic has warped around the pick ups due to heat . then again if it measures correct all round maybe not .. i do see they slope out so maybe a shim is missing on the spindle .. engineers blue would see where it is rubbing .
i think i might just try a thin shim on the spindle to see if it cures it

Hopewrecker
03-18-2012, 07:58 PM
Yeah, the magnet isn't separating from the platter at any point. Looks completely flush all around. I'm willing to try whatever. If I need to add a shim, I'm not too sure what this means and how I would go about it.
I really wish I could get into that housing unit to see if that would help. I really have no idea how to get in there and feel like I might be making things much worse.

??

petehall347
03-18-2012, 08:03 PM
shim is just a thin washer between the spindle and platter to raise it slightly .

boreas
03-18-2012, 08:33 PM
shim is just a thin washer between the spindle and platter to raise it slightly .

No, that's not the place for it. If you placed a shim there it would prevent the platter from fully seating on the spindle. If a shim is to be used to raise the platter it must be placed in the spindle well at the bottom under the spindle. Also, it shouldn't be a washer but a disc.

John

boreas
03-18-2012, 08:38 PM
I think these are the three screws that hold the motor assembly in place.

They are, but not the slotted end. Those are the ends with the bolts.

I don't know what you mean by slotted end or ends with bolts. Have you tried loosening those three screws to see whether the motor becomes loose? If so, try to slide the motor a hair away from the spindle and then retighten the screws.

John

Hopewrecker
03-18-2012, 09:11 PM
Okay, update:

I was able to loosen the screws to the motor casing and slide it around. I was able to move it away to totally eliminate the scraping. Now, it just keeps trying to reset itself. Instead of coming to a stop when the tonearm is pulled away, it just starts spinning again on its own. Then when I go to place the needle it automatically rejects it back.

Ugh.

Pio1980
03-18-2012, 09:40 PM
I think that's a separate problem unrelated to this one.

boreas
03-18-2012, 09:50 PM
Okay, update:

I was able to loosen the screws to the motor casing and slide it around. I was able to move it away to totally eliminate the scraping. Now, it just keeps trying to reset itself. Instead of coming to a stop when the tonearm is pulled away, it just starts spinning again on its own. Then when I go to place the needle it automatically rejects it back.

Ugh.

This is a new problem, right? Except for the scraping the table worked properly before?

I don't think this has anything to do with moving the motor. It's probably a linkage problem. Something may have got knocked out of position while you were working on it.

Okay, see the little metal plate on the white plastic cam? Push that away from the spindle until it stops. Now move the tonearm in toward the spindle. When you get close, about where the dead wax should be, the metal plate should swing toward the spindle.

Does it?

Okay, if it did, turn the spindle by hand (without the platter on). When the little tiny finger on the spindle gear hits the metal plate the turntable should start its shutdown cycle and the white plastic cam should start to spin as it engages the gear on the spindle. Keep turning the spindle. When the metal plate starts to approach the spindle again it should move back in away from the spindle.

I'm betting it doesn't.

John

Hopewrecker
03-19-2012, 11:30 AM
Success!!!!!

I want to thank all you guys for your help. John, you stuck with me and really helped me. Now, here's what's happened in case anyone else ever searches for answers to the same kind of problems on this kind of turntable.

Once I loosened the nuts holding the motor casing in place, it really messed with the speed. The magnet on the platter in relation to the sensors determines the speed and consistency. When I moved it far away, the platter actually spun backwards. When, I moved it closer again, one side was a little off and it wouldn't keep a proper speed. Finally, I loosened the nuts and moved the motor out a little, then I got a shoelace and wrapped it around the platter ring and then placed it on the spindle. Then I hoisted the whole thing up high hanging on a ledge so I can work on the underside (like a car). I pushed the motor against the platter and the shoelace insured I would get a constant distance all the way around and the thickness would be just slightly more than when I very first got this table in my possession. I held my breath and plugged it in, and started it spinning. While watching the strobe I could see that it was pretty damn consistent. I put the headshell and cartridge back on, put my slipmat, and pulled a record from the shelf. Placed the needle on the record and it sounds great!!! Speed is good and consistent on 45 and 33, it's not giving me any rejection problems, the automatic return works when it's supposed to.
Phew, that was a little project. Thanks again everyone. Beers on me.
:music::music::music:

boreas
03-19-2012, 11:38 AM
Success!!!!!
:music::music::music:

:thmbsp: Congratulations! Glad you stuck with it and ignored my suggesting that moving the motor didn't have anything to do with the problem. :)

John

jleon92f
03-21-2012, 07:31 AM
GOOD job!:thmbsp: