Sansui TU-999 tuning dial

[BostonBrian]

I was wondering if anyone has any dealings with a stuck, or binding tuning dial on a Sansui TU999? It seems to tune in the station correct by the numbers on the dial, but then gets a bit tighter and makes a noticeable ‘clunk’ before continuing on down, or up the dial. It doesn’t seem to slip, so much as bind, clunk, repeat.
Any ideas?

 

[chazix]

Any ideas?

My guess would be that the tuning cord is jumping over itself at the point where it has multiple turns around the shaft that's connected to the tuning knob. I think you'll be able to easily identify what's going on with a visual inspection of the internals.

What to do about it is a harder question. It might be worthwhile to very carefully get a small drop of oil into the ball bearing race(s) of the tuning capacitor, making very sure to not contaminate the vanes of the capacitor. Also anything else you can think of to reduce friction in other rotating parts like guide pulleys, again being very sure not to let any lubricants get where they don't belong.

It might also be that the tuning cord isn't under enough tension. I'm not familiar enough with the TU-999 to suggest how to address that.

 

[BostonBrian]

Thank you for the good ideas Chaz. Appreciate that. I had it open an didn’t see anything obviously wrong but I’ll try as you said an report back.

 

[DougBrewster]

I was wondering if anyone has any dealings with a stuck, or binding tuning dial on a Sansui TU999? It seems to tune in the station correct by the numbers on the dial, but then gets a bit tighter and makes a noticeable ‘clunk’ before continuing on down, or up the dial. It doesn’t seem to slip, so much as bind, clunk, repeat.
Any ideas?

I've seen that happen when the cord has been removed and rewound around the tuner knob shaft the wrong way. Is the item new to you or this this a recently developed problem?

 

[BostonBrian]

Hey Doug thx to respond. Yes it’s a new unit to me, been that way since I got it. It’s not like how when it gets to the ends of the dial tight, but binding once or twice throughout the entire range, then frees up.
Have you opened one to reverse the cord around the knob? Seems kind of sealed around the area circled in there last time I had it opened

 

[DougBrewster]

I had the same problem on a 9090DB after changing the cord. I used the diagram in the service manual to guide me but still got it wrong first time. I suggest you download the manual from hifiengine (no cost) and compare the images there with what you have. Particular attention needs to be paid to how it's rotated around the tuner knob extension..

 

[chazix]

how it's rotated around the tuner knob extension.

If the tuning pointer moves up the frequency scale when the tuning knob is rotated clockwise, then I think the aspect that's mentioned here is not a issue.

(I'd be fascinated if anyone can come up with an example of a tuning scheme where it is not true that clockwise equals higher frequency. Surely some iconoclastic brand must have tried that, but I'm pretty sure I've never seen it.)

 

[DougBrewster]

You're right, I put that badly chazix. The meaning I wanted to convey is that it's quite possible to install the cord on the tuner knob axle the "wrong way" by starting the cord installation at the wrong axial end of the tuner knob extension. That way you would still have the correct knob/cord rotation but the cord would be slightly mis-aligned on the shaft and tend to climb over itself.

 

[BostonBrian]

Very thankful for all the suggestions. I have the manual and it shows the correct alignment of the tuning cord around the pulleys. It’ll have to wait until this weekend when I’m off to open and verify what’s going on. I’ll keep you updated.