Kenwood kd -990 solenoid defective?

[TrevorBarten]

I recently bought a kd 990 second hand for a pretty good deal however the arm cueing isn't working. I did some testing and I am pretty sure that the solanoid is defective. It measures 0.6 M ohms and doesn't do anything at all. Is there any chance of finding a fitting replacement? Also the auto stop did work at first but not anymore, anyone know why that could be ?

Included are some pictures of the solanoid.

 

[BillWojo]

If you can't find donor parts can you get the bobbin out of the solenoid? Certainly sounds like it fried.
If you can get it out, I'd try rewinding it as a last resort. Measure the wire gauge size or have it measured, unwind the coil to get a length, might even find the break at the beginning of the coil if your lucky. Use enamel magnet wire.

BillWojo

 

[salamander]

I recently bought a kd 990 second hand for a pretty good deal however the arm cueing isn't working. I did some testing and I am pretty sure that the solanoid is defective. It measures 0.6 M ohms and doesn't do anything at all. Is there any chance of finding a fitting replacement? Also the auto stop did work at first but not anymore, anyone know why that could be ?

Included are some pictures of the solanoid.

I see that you removed the mirror and the optical sensor . Mirror , optical sensor and solenoid - together perform the function of automatic lifting . The solenoid can be rewound . I am sure that you will not be able to buy exactly the same solenoid separately from the player .

 

[salamander]

Here is the marking on the solenoid of my Kenwood KP770d . He has the same vin number. Probably the same is in Kenwood KD 880 . But it 's easier to rewind the solenoid coil .

 

[TrevorBarten]

Here is the marking on the solenoid of my Kenwood KP770d . He has the same vin number. Probably the same is in Kenwood KD 880 . But it 's easier to rewind the solenoid coil .

That looks like the exact same mechanism. How much does the solenoid on the kd 770 measure? I had contact with the seller and they mentioned thee solenoid had already been rewound. And yes I did remove the optical sensor but after reassembly it did work like twice until it stopped.

 

[TrevorBarten]

If you can't find donor parts can you get the bobbin out of the solenoid? Certainly sounds like it fried.
If you can get it out, I'd try rewinding it as a last resort. Measure the wire gauge size or have it measured, unwind the coil to get a length, might even find the break at the beginning of the coil if your lucky. Use enamel magnet wire.

BillWojo

How would I go about doing this ?

 

[TrevorBarten]

I see that you removed the mirror and the optical sensor . Mirror , optical sensor and solenoid - together perform the function of automatic lifting . The solenoid can be rewound . I am sure that you will not be able to buy exactly the same solenoid separately from the player .

I tried to recalibrate it according to the service manual, which I found quite difficult to do as I could not get the arm to stay in place properly. But aside from that I did manage to (I think) get the proper calibration of 0.9 V at around 6 cm from the spindle but still didn't turn off, another thing to note would be that the voltage increase drastically beyond the 6 cm point (from 0,8-1V to around 3V). I did get it to turn of a few times at the incorrect distance (usually closer to the spindle) when fiddiling around with the potentiometer but I cannot seem to replicate this consistently. But my point here is that the optical sensor does seem to work. Any clue on what the issue here could be? Maybe a wire that has a bad connection? It's quite a pain to get to the underside of th PCB. Do you maybe have a picture of the internals of your kd 770?

 

[salamander]

That looks like the exact same mechanism. How much does the solenoid on the kd 770 measure? I had contact with the seller and they mentioned thee solenoid had already been rewound. And yes I did remove the optical sensor but after reassembly it did work like twice until it stopped.

Now I can 't measure the nominal resistance of the solenoid coil . I took a photo of the solenoid a long time ago - when I was doing full maintenance of my turntable . Now the turntable is assembled, configured and I don't want to disassemble it anymore ...... BUT - the resistance of the winding itself will not give you anything. When rewinding , it is necessary to observe the number of turns ( and the diameter of the wire ) - as it was in the original . For different types of wire , the resistance may vary . The coil of such a solenoid can have several thousand turns .

 

[salamander]

I tried to recalibrate it according to the service manual, which I found quite difficult to do as I could not get the arm to stay in place properly. But aside from that I did manage to (I think) get the proper calibration of 0.9 V at around 6 cm from the spindle but still didn't turn off, another thing to note would be that the voltage increase drastically beyond the 6 cm point (from 0,8-1V to around 3V). I did get it to turn of a few times at the incorrect distance (usually closer to the spindle) when fiddiling around with the potentiometer but I cannot seem to replicate this consistently. But my point here is that the optical sensor does seem to work. Any clue on what the issue here could be? Maybe a wire that has a bad connection? It's quite a pain to get to the underside of th PCB. Do you maybe have a picture of the internals of your kd 770?

If you have an ESR-meter, check all the electrolytic capacitors on the board. And look at the soldering quality on the board . Over time , the solder may change its properties , possibly a bad contact on the board .

 

[salamander]

...... Do you maybe have a picture of the internals of your kd 770?

Unfortunately , I didn 't take detailed photos . Photographed only the motor and the elements of the lift . These are the photos . But I have a photo of the insides of the 880 model ( copied from the internet ) . The 880th is similar to the 770th Kenny . The same motor , the same tonearm and the same electronics board . But , probably , it can be very different from your 990th .

 

[BillWojo]

Expect the solenoid coil to have a resistance of no more that a few hundred ohms. 0.6Mohms (600,000 ohms) is way to high.
As to how to get it out? You need to study it and see how it was assembled. Post pictures on here as well.

BillWojo

 

[TrevorBarten]

Expect the solenoid coil to have a resistance of no more that a few hundred ohms. 0.6Mohms (600,000 ohms) is way to high.
As to how to get it out? You need to study it and see how it was assembled. Post pictures on here as well.

BillWojo

I was more talking about the rewinding part. I have never done it before. Should I use a drill or do it by hand ?

 

[TrevorBarten]

Unfortunately , I didn 't take detailed photos . Photographed only the motor and the elements of the lift . These are the photos . But I have a photo of the insides of the 880 model ( copied from the internet ) . The 880th is similar to the 770th Kenny . The same motor , the same tonearm and the same electronics board . But , probably , it can be very different from your 990th .

I see. It does look different from the kd 990 but the pcb is quite similar and the arm assembly looks identical. I think everything on mine is original but I can't say for certain. I am a bit suspect of the wires running over the pcb but the soldering looks factory and the wire colour is the same as the green solenoid wire (which is also green in the pictures you sent). I do not have an ESR meter but I have been looking into getting one so might as well pull the trigger now.

 

[salamander]

I was more talking about the rewinding part. I have never done it before. Should I use a drill or do it by hand ?

Usually , a very thin wire ( 0.1-0.2 mm in diameter) is used in such coils . Therefore , the winding should be careful not to break the wire . You should not use a drill . For winding such coils ( and transformers ) I use a small machine with a counter of turns . This machine is mounted on the table like a vise . The machine is manual . He is over 40 years old . Probably something more modern is being sold now.

 

[BillWojo]

Yea, you can rig something up if your handy. Some sort of hand crank. As far as wire, get someone who can measure accurately to figure out the gauge size. Carefully pull off the insulation from the old coil and unwind it. As long as your in the ball park it should work fine.
You might find the beak in the wire at or near the beginning, if so just repair the break.

BillWojo