View Full Version : Kenwood KD-850 questions


Everman
09-30-2009, 01:32 AM
Hey all. I'm new to the forum. I just picked up a KD-850 from a friend. He hadn't really tested it, other than the table spun. I wanted to go through it and get everything tested and working.

I found that pressing the Play button started the table turning, and lifted the tonearm, but the tonearm didn't swing out into position. The tonearm lifter also raised *very* slowly, to the point where sometimes it just didn't move at all. But I had seen it move at least once, so as far as signal goes, it seemed to be working.

I know you can just lift the tonearm and place it on the record and use the deck manually. I just wanted to see if I could get everything working. I also noticed that the right most button on the front (FAST ->) was really sticky.

I decided to go through the service manual troubleshooting and try to determine the problem. I ran through the flow diagram on pg. 17. That led me to a few questions. When it is asking if the pin is "H"igh during the first 3 question boxes, I am measuring 15v on each pin. That might be because I am taking GND from the lead that runs to the metal back of the deck. I figured that was a pretty solid GND. The question then comes when I measure the last flow chart question "Is J9 (Black) approx. 7.5v?" I actually measure 9v. But the thing that makes me wonder is that I measure 5.5v on that J9 when the tonearm is moved out and placed back at rest, effectively stopping the Play command. The 5.5v is present as soon as the deck is powered up as well.

So, I don't think I am measuring from the right GND. Can someone direct me to a good GND to use during these tests? If I am using the right GND, I think I am only getting an additional 3.5v when it is meant to spin the motor. If I measure the voltage on the RED wire (also going to the motor), it also has 5.5v on it in a steady state. When the Play button is pressed, the voltage on it goes to 1.5v. This leads me to believe that I have a voltage across the motor of 7.5v, which is what the troubleshooting guide is asking me to look for. This being the case, the guide says my motor is bad. Anyone know where to get one?

One other question arose. I went to free up the sticky -> button at the control panel. Without thinking much, I poured 1/2 capful of alcohol in there and cycled the button. It free'd up just fine. The problem is the beautiful acrylic / plexi front panel windows started clouding up. I frantically pulled apart the entire button assembly, so now I have the two plexi pieces out, but they have cloudy spots on them. How can I fix / clean / repair these? I am sooo kicking myself for not thinking that one through... =(

Anyway, I am sure I didn't describe my work very well, so I am sure you will have more questions requiring me to clarify. Thanks for reading. =)

EchoWars
09-30-2009, 01:40 AM
You're probably a lot deeper than most people here are willing to jump into a complicated digital-control T-Table. I will suggest that, if you decide to tackle this project, you'll probably be on your own.

That said, I wish you luck!

Everman
09-30-2009, 01:57 AM
Ah, ok. I suppose I should have boiled down that post to two questions:

1) Where can I get a replacement tonearm motor for a KD-850
2) How do you "clean" or de-cloud the acrylic / plexi that is found on the front button panel once it has come in contact with alcohol?

I tried toothpaste, but I just wore down my fingertips... =(

Sam Cogley
09-30-2009, 02:31 AM
1) Where can I get a replacement tonearm motor for a KD-850

Watch eBay for a working replacement. I found the auto-drive motor I needed for my KD-3055 there.

redcoates7
09-30-2009, 01:06 PM
silly question here, but all the belts are good and there's no slippage? I realize you most likely would have heard something as the motor started spinning if so, but had to check.

Everman
09-30-2009, 02:13 PM
silly question here, but all the belts are good and there's no slippage? I realize you most likely would have heard something as the motor started spinning if so, but had to check.

No worries, thanks for the question. I don't have any motor movement at all. I have the back panel off, so I am watching the activity when Play is pressed. The voltage across the motor goes from 0v (+5.5v to GND on each lead, so a voltage across the motor of 0v) to +7.5v (+9.0v on the black lead to GND and +1.5v on the red lead to GND) but no motor spinning action.

To summarize the earlier post, I traced through the troubleshooting guides suggestions for measuring if select pins were "H"igh or not after Play was pressed.

Now that I think I have it narrowed down to the problem, I can keep my eye out for an older unit / working motor on eBay.

My bigger problem now (funny enough) is trying to get the cloudiness off the acrylic front panel that *I CAUSED*! Man I am disappointed with myself. Nothing like causing yourself more problems when trying to fix something. =)

Sam Cogley
09-30-2009, 02:30 PM
silly question here, but all the belts are good and there's no slippage? I realize you most likely would have heard something as the motor started spinning if so, but had to check.

KD-850 is direct-drive, if memory serves.

Everman
09-30-2009, 03:00 PM
KD-850 is direct-drive, if memory serves.

Yes, the platter is DirectDrive, but the tonearm motor is connected to a gear with a thin 2" belt.

4dryhme
09-30-2009, 03:10 PM
...per the cloudyness on the acrylic: Don't believe that can be repaired or buffed out. However, with the strong likelihood that I am mistaken you might peruse the cleaning the turntable cover sticky above. Personally I would just take it to a plastic dealer and have them cut you a new piece to that size and thickness. Depending on how it's mounted in the case a similar size piece of glass might also work and be less subjected to scratches in future.

Sam Cogley
09-30-2009, 04:17 PM
Yes, the platter is DirectDrive, but the tonearm motor is connected to a gear with a thin 2" belt.

Interesting. Most direct-drive full-auto TTs I've seen use a gear or cam system to drive the tonearm, with the exception of linear trackers. Always good to learn something new in case I run across one. :thmbsp:

Balifly
09-30-2009, 05:49 PM
My bigger problem now (funny enough) is trying to get the cloudiness off the acrylic front panel that *I CAUSED*! Man I am disappointed with myself. Nothing like causing yourself more problems when trying to fix something. =)

Have you try " Meguiar's PlastX " the clear plastic cleaner & polish.
That's the polish for the turntable dust covers.
It work very well with the cloudy covers on my old turntables.:thmbsp:

Hope it works for your acrylic front panel.
Take a look at the " sticky " at the top of the opening page.

hakaplan
09-30-2009, 06:34 PM
Interesting. Most direct-drive full-auto TTs I've seen use a gear or cam system to drive the tonearm, with the exception of linear trackers. Always good to learn something new in case I run across one. :thmbsp:
Weren't you working on a PS-X70? Isn't that an independently driven arm?

Everman
09-30-2009, 09:13 PM
silly question here, but all the belts are good and there's no slippage? I realize you most likely would have heard something as the motor started spinning if so, but had to check.

Ok, Redcoates gets the prize. :thmbsp:

Duh... the motor was spinning for each test! Slippage! I would have thought I would have heard the motor spinning as well, or at least seen the axle turning... Nothing. Silent. Perfectly balanced. Spinning away.... LOL

So my belt is pretty much toast. I have seen belts online for $17-$20. Are there other alternatives, or do I have to get scalped for 3g rubber band?

Thanks to all who were pitching in. I guess that is why all the signals were good. HAHA

Now for that acrylic! =)

Everman
09-30-2009, 09:15 PM
Have you try " Meguiar's PlastX " the clear plastic cleaner & polish.
That's the polish for the turntable dust covers.
It work very well with the cloudy covers on my old turntables.:thmbsp:

Hope it works for your acrylic front panel.
Take a look at the " sticky " at the top of the opening page.

My boss is bringing in some acrylic polish he got from a plastic supplier in town. Hopefully he remembers tomorrow. I don't have to worry about reassembly until I figure out the belt situation, so I have some time.

The good news is that I will probably have the table up and fully functional soon!

Follow up question. Do any of you have experience verifying motor speed and calibrating the Phase Locked Loop?

Sam Cogley
09-30-2009, 09:38 PM
Weren't you working on a PS-X70? Isn't that an independently driven arm?

Yep, but it's a worm gear/cam drive - no belts. Same with my belt-drive Kenwood KD-3055. The PS-X50 has a single motor, but the return-only arm is again cam-driven from the platter. The only auto in my possession with belts on the arms is the QL-L2.

I just realized something rather humorous - my KD-3055 is a belt-drive TT with a direct-driven arm. The KD-850 is a direct-drive TT with a belt-driven arm. Kenwood was very odd at times. :screwy::headscrat

Anyway, I stand by my advice - if the motor is the problem, finding someone who is parting out that model TT is your best bet for a fix.

Everman
09-30-2009, 10:10 PM
Yep, but it's a worm gear/cam drive - no belts. Same with my belt-drive Kenwood KD-3055. The PS-X50 has a single motor, but the return-only arm is again cam-driven from the platter. The only auto in my possession with belts on the arms is the QL-L2.

I just realized something rather humorous - my KD-3055 is a belt-drive TT with a direct-driven arm. The KD-850 is a direct-drive TT with a belt-driven arm. Kenwood was very odd at times. :screwy::headscrat

Anyway, I stand by my advice - if the motor is the problem, finding someone who is parting out that model TT is your best bet for a fix.

Thanks, but I figured it out. The motor was fine all along. The belt was shot. I just couldn't see the shaft spinning, and it was dead silent.

Now for a recommendation on a belt dealer?

Sam Cogley
09-30-2009, 10:19 PM
Thanks, but I figured it out. The motor was fine all along. The belt was shot. I just couldn't see the shaft spinning, and it was dead silent.

Now for a recommendation on a belt dealer?

I've bought belts for various pieces of gear from stevelc on eBay. He has great customer service and a very wide array of belts.

No affiliation with the seller except as a satisfied customer. :thmbsp:

Everman
10-01-2009, 12:56 PM
I can't find any listings for him at the moment. I will keep an eye out. Meanwhile I found LPGear.com has the belt listed that I am looking for. They want $12 + shipping for it, so I may just go that route.

Blue Shadow
10-01-2009, 03:53 PM
marrscommunications has belts also. ebay or info@marrscommunications.com will get you an answer.

redcoates7
10-01-2009, 04:02 PM
Last time i needed belts I bought a whole belt kit from MCM...

http://www.mcmelectronics.com/search.aspx?C=&K=belts&T=

IIRC, I used one of them for the exact same repair of one of my KD-850s!

It's a great 'table, hope you enjoy it!

BrocLuno
10-01-2009, 07:17 PM
Welcome aboard :)

You might email Steve at TurnTableNeedles.com. He sels parts and electronics as his other business and can sometimes come up with things you don't expect. He has free shipping on small parts like this.

You might try a rubber band to see if things work as desired? It's not a long term fix, but worth a test?

Do things move freely, or do you need to do some clean and lube?

Nice table by the way - good if you can get it sorted :)

Everman
10-02-2009, 09:00 PM
Welcome aboard :)

You might email Steve at TurnTableNeedles.com. He sels parts and electronics as his other business and can sometimes come up with things you don't expect. He has free shipping on small parts like this.

You might try a rubber band to see if things work as desired? It's not a long term fix, but worth a test?

Do things move freely, or do you need to do some clean and lube?

Nice table by the way - good if you can get it sorted :)

Thanks! I just ordered the belt listed on their site for the KD-850. The description asked for the buyer to tell them what the belt was for so they could update the site. I let them know it was for the tonearm motor. I hope it is the right one.

Now for your other question. I did need to oil some shafts etc. I also put a few drops on the tonearm lift cylinder shaft. It freed it up tremendously... to the point where the arm lifts quite quickly now. Is this normal? Should I have not freed it up that much?

Everman
10-04-2009, 06:06 PM
Don't mean to shamelessly bump, but just wondered if what some of you Kenwood owners thought about the issue with the tonearm lift shaft now popping up quite quickly after oiling it...?

EchoWars
10-05-2009, 02:15 AM
Possible that the shaft is supposed to have 300,000wt or 500,000wt silicone oil rather than 'normal' oil.

bolly
10-05-2009, 05:34 AM
TA lifter info: http://www.audiokarma.org/forums/showpost.php?p=1175518&postcount=40

dbf909
10-05-2009, 02:27 PM
If the 850 uses the same cueing mechanism as the 750 then you need to completely disassemble it, clean it out really good, and put it back together using the proper 300,000 wt silicone damping fluid. I did my 750 using 500,000 (it's what I had on hand) and it's a bit slow but I can live with it.

You can get the silicone damping fluid at a hobby shop that deals with RC Cars - they call it "Silicone Differential Fluid". They have lots of thinner grades but it has to be 300,000 wt or it will still move too fast.

It is possible though that the 850 uses a different mechanism since it is auto (the 750 is manual only). If that is the case, never mind...

Everman
10-05-2009, 06:01 PM
Thanks for the referrals. I just ordered some 300,000wt damping fluid from amainhobbies.com (http://www.amainhobbies.com/product_reviews.php/cPath/1_167_297/products_id/6934/n/Kyosho-Silicone-Differential-Oil-300000wt--40cc). It was ~ $14 + $4 shipping.

I will probably get it next week some time, and I will let you guys know how it works.

Everman
10-08-2009, 10:28 PM
I just received the square belt and some new needles. I have the table up and running, but don't have the feet on yet as I have to take the back off and apply the silicone damping fluid when it gets here.

Do you guys have any advice as to how to apply it? Have any of you removed the assembly? Thanks.

redcoates7
10-09-2009, 11:52 AM
Haven't done this myself, but should. Sorry I can't be more help!

bolly
10-09-2009, 01:05 PM
I have disassembled mine from my KD-650... post a pic of yours I'll tell you if they're the same

dbf909
10-09-2009, 06:13 PM
On the 750 the cueing assy can be removed and dissasembled pretty easily. Note that the KD-750 uses a Kenwood arm. I'm not sure that it is the same as the 850 the the basic rebuild should be close.
1) First, the lift guide (curved metal piece on top) is removed from the cylinder by removing the single screw from the top.
2) Next, the cylinder is removed from the frame by loosening the two set-screws that adjust the height and dropping it out the bottom of the frame. I had to raise the tonearm up out of the base an inch or so to provide adequate clearance for the cylinder to come out the bottom of the frame. Note the height of the cylinder. When you re-assemble it, you want to put it back to the same place.
3) Next, the top of the cylinder can be unscrewed kind of like a cap.
4) Inside, there will be a spring on top of the piston - this spring pushes the piston back down when the lever is dropped. Remove this spring and clean off any gunk that is there. Be careful not to damage or bend it.
5) Next, pull the piston out. You can use the screw that goes into the top to give you something to pull on. It should come out easily.
6) Under the piston is a smaller stiffer spring and a nylon cup that retains this spring inside the bottom of the piston. This spring allows the lever to be raised quickly but the piston to move up slowly. Clean all of these parts as best you can. I actually used WD-40 as a cleaner and then wiped everything down with a cotton towel.
7) There will be some gunk still inside the bottom of the cylinder down where the cam rotates based upon the lever position. It's also important to clean this out as well - the WD-40 sprayed in there worked well to blast out the gunk. I dried it as well as I could using Q-Tips.
8) Using a toothpick I put some of the damping fluid down around the cam in order to give the lever a little resistance to movement. You don't want to put too much, just on the bearing surfaces. I found the first time I did one of these, that without this, the lever would tend to drop all by itself.
9) Also put a little bit on the bottom of the plastic cup where it touches the lifting cam. I did not put any on the lower spring.
10) Put damping fluid on the outside of the piston forcing as much as you can in the rings or grooves - coat the whole piece - this is the key to the whole thing.
11) Slowly and carefully insert the cup, lower spring, and piston back into the cylinder. You will feel the friction created by the damping fluid as you insert it. Wipe the excess off the top of the cylinder near the threads.
12) Replace the top spring and the cap - make sure that the top spring is correct. I believe that the largest end goes up.
13) At this point you should be able to move the lever up and down as see the piston responding properly. Double check that everything was put back together properly.
14) Re-assemble the cylinder back into the frame and the lift guide the same as it came out.
15) Adjust the cueing height as necessary by moving the cylinder up and down in the frame and locking it in place with the two set-screws.
16) Enjoy your TT...

Everman
10-10-2009, 06:32 PM
Wow thank you for the amazing detail. I haven't received the damping fluid yet, so I haven't torn down the unit again. I have been playing some vinyl in manual mode until the damping fluid gets here. Then I will get into the back again and post up some pics before I get started.

Thanks again!:thmbsp:

dbf909
10-11-2009, 12:20 PM
Definitely post some pics. Depending on the specifics, it may differ slightly from my description above. The disassembly/assembly may be different but the basic concept will be the same...

Everman
10-13-2009, 09:24 PM
Here is the overhead of the tonearm assembly and the lower view. It seems to me I need to unscrew the cap on top of the piston and remove the brass colored lifter arm on the bottom to remove the piston. Does this one look familiar to you? It seems you had several more steps, including two springs etc.

Everman
10-13-2009, 10:22 PM
I took the brass lifter tab assy off, but I can't get the white plastic tab off the bottom of the piston. I think I need to get the "dressed" screw (cover with two small holes) off the top side of the piston. I think that would allow me to drop the piston out the bottom and clean it. I bet I need a special dressed screw screwdriver that I don't have (of course).

dbf909
10-13-2009, 11:43 PM
Based upon your pics, the 850's cueing mechanism is totally different from the 750. You can disregard most of my procedure above.

I think that you are correct though, you need to get that screw off the top and remove the piston from the bottom to take it completely apart.

However, if you can get some of the damping fluid into the cylinder around the brass piston from the top, it may be enough to make it work properly. You might try that first before you go find or make something to get the fastener off.

I have seen wrenches that are designed for those types of screws but you may be able to get it with a pair of really small needle-nose pliers. If it's too small for that, you might be able to modify an old flat-blade screwdriver to do it.

bolly
10-14-2009, 05:04 AM
different than my 650 as well everman, but similar

Everman
10-14-2009, 08:46 AM
Thanks you guys. I was thinking about getting some fluid down in the channels by just lifting it as high as I can, as in one of the previous pictures. I guess that wouldn't hurt anything, because if I don't like the behaviour, I can always proceed to take it apart.

I think technically I should be able to load up those channels with fluid without too much issue. The problem I would see, which is why I would rather take it all the way down, is that I need to remove the last of the oil residue that I put on it to free it up back when I got it.

Do you think a coating of light oil on the piston would somehow prevent the fluid from sticking to the piston / staying in the channel and doing its job?

bolly
10-14-2009, 12:00 PM
everman, you try cleaning with a q-tip and alcohol? or a qtip stick(pegwood) wrapped in lens cleaner soaked in alcohol :) to try and mop out the cylinder first?

bolly
10-14-2009, 12:09 PM
(cover with two small holes)

there was a circlip on mine I removed

Everman
10-14-2009, 03:05 PM
bolly, I will try to clean it out with a q-tip (or similar). I also have a friend looking for a spanner wrench for me that will fit.

I had a question on the hinge repair that you had done. What material is on the back that is shaped and painted? I need to do the same thing to my hinges.

Also, what is the little hole in the back left corner of the TT body? It looks like you have the same black plastic hole back there that I do. I don't know what it is for.

bolly
10-14-2009, 05:21 PM
the black stuff is a 2-part epoxy. I used steel putty by Devcon.

ahh that hole lol

...I can't remember but it's typed out here somewheres

Everman
10-14-2009, 10:55 PM
Thanks Bolly. I just ordered some Plastic Steel Putty by Devcon. That stuff looks tough. My hinges need it. One of them is completely broken in two pieces. I hope it works, but even if it doesn't I could probably use it around the house at some point.

Everman
10-15-2009, 09:31 PM
Bolly, the service manual calls the hole a "Shell Stand". Any idea what that means?

dbf909
10-15-2009, 10:54 PM
It is used to hold a spare headshell. The connector end of the headshell fits into the hole and holds it with a cart mounted...

EchoWars
10-15-2009, 11:31 PM
Mystery solved. I wondered that myself.

Everman
10-15-2009, 11:53 PM
Too cool! That is a great idea. Thanks!