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Kenwood KX 9050 auto stop too sensitive.

Hi All,

Bought a Kenwood 3 head cassette tape deck for a very reasonable price.
It is almost mint, but I have one issue: the auto stop feature is much too sensitive. With most recorded cassette, the tape keeps stopping every slightest tension increase.
My question: is there a way to adjust the auto stop minimum/maximum tension for recording as well as playback.
I downloaded both owner and service manuals, but couldn't find any info about this.
Thanks very much in advance for any hint!

Cheers,

Hugh.



karodimitrov's picture

Re: Kenwood KX 9050 auto stop too sensitive.

I think you should open the mechanics of the deck and clean carefully two spindles(reel stand) with cotton and alcohol.The auto-stop is optron and if black-white sectors are dirty will not work correctly.Thoroughly clean both optrons of the circuit board, which is on top of the spindles(reel stand)-dirty with grease and dust.

Re: Kenwood KX 9050 auto stop too sensitive.

Thanks a lot for your quick answer, Karodimitrov!
Will open the deck and thoroughly clean the parts you mentioned.
Do I have to take the whole mechanism out?
Will study the service manual first. I'm afraid I'm more mechanical minded than elecrtronic, so, as long as the issue can be solved with mechanics only, I run a good chance to cure the problem.
Will keep you informed as soon I find time to start with this beast. Currently busy with two Dual's (1218 and 1219) full servicing and restoration.
Thanks again.

Cheers,

Hugh.

karodimitrov's picture

Re: Kenwood KX 9050 auto stop too sensitive.

All the mechanics comes out as a separate unit.It is even easier.Check the belts too.

karodimitrov's picture

Re: Kenwood KX 9050 auto stop too sensitive.

Cheers and good luck.

Re: Kenwood KX 9050 auto stop too sensitive.

Thanks!
Will report soon.
Cheers,

Hugh.

Re: Kenwood KX 9050 auto stop too sensitive.

Hi All,

Spent a couple of hours taking the mechs apart and cleaning all the parts I could reach with isopropyl alcool.
Still, some cassettes are unplayable, keeping stopping all the time, even in FF function.
The same cassettes are working without problems on both my Marantz Mod 5020 and SD 230.
Some of them are quite old but valuable for their content.
Could there be any adjustment device to lower the tape tension sensitivity?
Thanks for any more info!

Chers,

Hugh.

karodimitrov's picture

Re: Kenwood KX 9050 auto stop too sensitive.

Apparently not optrons. Other I can think of are friction felts under spindles. or belt.Everything else is electronic-which no adjustment.

Re: Kenwood KX 9050 auto stop too sensitive.

Well, stupid bl...y electronics!
Wonder whether these were already programmed to become obsolete after 10 years or so...
When I have some time, will try again and take the whole shlimblik apart...
Thanks again Karodimitrov for your kind help! Could have to come back again if I find myself with all sorts of unknown bits and pièces lying around at the time of reassembly.

Cheers,

Hugh.

Re: Kenwood KX 9050 auto stop too sensitive.

Sounds like the clutch tension of the take-up reels is to light. There could be a couple of reasons why, as well as possible other problems, all depending.

A quick check that can help determine which can be done by simply watching the take up side of the tape while it is playing. If it appears to be somewhat jerky or not at a constant speed, more than likely reel tension is the cause. This will be easier to see when you are at the end of the tape. (More weight for the reel to pull). An older factory tape, 90 min or better is best for this test.

If the reels are gear driven, more than likely it will be with the clutch of the reel itself. If they are belt or idler driven, you may simply have a bad belt or idler tire. If a tire, sometimes a very light sanding with an emery board can resolve the problem for a while. There are also asst chemicals that can soften the rubber and resolve the issue, depends on how hard the rubber is. Also the tension spring on the idler may need adjustment. If it is a belt you can fudge a hair on the belt diameter, usually not smaller. Most belts I have seen are .047 . I have been out of this end of the business for a while, but I think that MCM Electronics still carries some belts.

Another cause can be the motion detector. These vary widely, from mechanical to electronic. I have seen a few that tension was okay, and the reel sensor was bad and\or dirty. These sensors can be optical (photo xistor and emitter pair) or magnetic (hall effect device). These devices usually are located under each reel, mounted on the base plate, and removal of the reel is necessary to see them. The hall devices typically have 3 leads and will stick out apx 3 mm from the solder pads. Optical's will be small round with 1 flat side black devices with 2 epoxy type lenses. If optical, the bottom of the reels will have several silver and black bands, much like a strobe-a-scope, confirm that these are not dirty or the reflective portions are in good shape. Electronic motion detectors usually operate by resetting some sort of timer each time a pulse is detected. If it's output stays high or low too long, then the timer reaches it's limit, resulting in "STOP". Usually this is 2-3 seconds, but some of the computer controlled are much more precise, as they tend to look at movement of both reels and then calculate when there is an issue, and stop within 1/2 sec.

I am not familiar with this particular model, and did not find a manual for it, but some reels are adjustable, especially on higher end equipment. These fall into 3 different basic styles.

1st; typically has a metal insert disc that sits just under the spring, on top of the reel base, (usually copper), with 3 tabs. These tabs rest in different height ridges in the base of the reel. It can be tricky to lift the tabs to rotate the disc to a higher notch, a lot easier when decreasing the tension, (lower notches). These are found in Matashita\Panasonic built mechs.

The 2nd type clutches simply use a spring which it held in place by a small cap/plug that snaps into the top of the reel. (NOTE that the 1st style also uses the same type cap). The top of the reel can split, allowing the cap to not seat correctly... causing the clutch to slip before it should. Usually these are made of nylon, and can be difficult to repair. Mainly due to the piece that slides on the spindle, (the little gear looking part that actually makes contact with the inner portion of the cass tape reel). I have had some success with melting the split using a small soldering iron, then sanding down the seam so that the spindle moves freely and the cap stays seated. Stupid glue and such are useless as they will not adhere to the nylon. (mentioned as a last resort... if the cap only partially seats, in other words, will hold together enough to keep the reel assy from flying aprt, but not seat all the way, you can stretch the spring a tad. But in doing so, can create more pressure on the cap, making the problem worse, and can result in excessive tension of the clutch as well as putting the reels assy in a bind, as the split ring is all that is holding it together, and extra drag is intruduced).

The 3rd type is much like the 2nd, but the cap that hold the reel assy together is on the bottom of the reel, and suffers the same failure, split nylon. This style is easier to repair cuz you only have to worry about the seam against the bottom of the reel, (which many times will be against felt), and clearance with the base plate.

As far as adjustment on the later 2 styles, it varies, a good visual inspection will usually find it's secret.

Use care when removing the reels, most are usually held in place by a small nylon split ring. If the reel is split, when the split ring is removed, parts will fly. A small piece of good vinyl tape wrapped around the spindle, being sure to have good contact with the (the little gear looking part that actually makes contact with the inner portion of the cass tape reel) and the spring\reel base, BEFORE removing the split-ring, can save a major headache in trying to find all the parts that went flying into never never land.

Also excessive reel tension will damage your tapes, will stretch the hound out of them and typically results in eating the tape, as it will ride up on the capstan.
If memory serves, reel tension should be between 60 - 80 grams for most decks. but even at 80 grams, some 120 min tapes can still have problems as you reach the end of the tape. I don't recommend the use tapes longer than 90 min.

Hope this helps. If you can send a pix of the mech assy so that I can see what type reels you have, I may be able to offer more info.

Have a great day
Chaz

Re: Kenwood KX 9050 auto stop too sensitive.

Hi Chaz,

Thanks for your extensive lecture.
Will get back at the deck ASAP and check the points you mentioned.
Actually, both the user's and service manuals are available on this site.
That should already give a partial answer to the questions regarding the type of mechanism used here.
Do you think you could do like some of the knowledgeable Vinyl Engine guru's do: refer to service manuals part numbers to describe the actions which should be done to correct the failures?
Dualcan, for instance has helped the Dual turntables community a lot with this method, plus detailed pics on "how to's".
Will get at the beast and start disassembling the mechanical parts again, but I'm absolutely useless at electronics, I'm afraid. Will try and take some pics as well.
Many thanks again for your input!
Will get back.

Cheers,

Hugh.

Re: Kenwood KX 9050 auto stop too sensitive.

Karodimitrov and Chaz: Finally re-opened the reachable mechanical parts and found that the capstans and rubber rollers were still dirty in spite of my first cleaning.
So I managed to make it spin while using q-tips with plenty of isopropyl alcool on the dirty parts. Almost needed a third hand but I succeded and... miracle! most cassettes play without popping out, FF and rewind as well.
Also had issue with the lid opening, which got cured by cleaning the belt and pulleys with alcool.
So, hopefully I can consider recording without unwanted stops.
I want to thank both of you once again for giving me some hints!

Cheers,

Hugh.

karodimitrov's picture

Re: Kenwood KX 9050 auto stop too sensitive.

Cheers,Hugh!