Pulley Creep

[boreas]

Hi, all. First post to the Tuners forum but I just got my first analog tuner, an Onkyo T-4090. It seems to be in good shape overall but there's one problem I can't seem to get a grip on.

The dial pulley, or more accurately the shaft for the dial pulley, Gradually backs itself out of the tuning cap. After a time or two up and down the dial it has backed itself out far enough that the flats on the shaft no longer engage the small gear that spins the tuning cap.

I should mention that I had to reinstall the dial cord and, though the dial works correctly, I can't help thinking the problem is somehow related to the reinstalled cord.

Any help will be greatly appreciated.

John

 

[Dave_1962]

Sounds like too much tension on the cord - that was the case for me once. I solved it with a dab of loctite first and restringing as loose as I could get away with. Wound up (no pun intended) stringing it 4 or 5 times to establish parameters of too tight and too loose. First off the white plastic piece with the spring on it that mounts on the shaft is called the drum and the dial pulleys are the much smaller wheel type guides for the cord. You have three of them - make sure they are moving freely and are lubed. It also looks by the pic that the cord is wound onto the drum towards the outside edge farther from the shaft rather than towards the inside or nearer to the shaft. I would make sure you get it as close to the inside as you can. Also double check the lock screw is biting down on the flat so the drum cannot spin on the drum - do this first.

 

[boreas]

Sounds like too much tension on the cord - that was the case for me once. I solved it with a dab of loctite first and restringing as loose as I could get away with.

That could be it. The pulley has several holes all around it, 6 or 8 of them. I moved the screw from it's original hole to the next because the cord felt a little loose. I'll mobe it back and see what happens.

It also looks by the pic that the cord is wound onto the spool towards the outside edge farther from the shaft rather than towards the inside or nearer to the shaft. I would make sure you get it as close to the inside as you can.

I moved it it to the inside once and it moved itself back.

Also double check the lock screw is biting down on the flat so the spool cannot spin on the shaft - do this first.

I already did that. I re-positioned the pulley on the shaft, tried several different positions on the shaft, trying to make angle between the string and the shaft 90 degrees or less. It didn't work.

To be clear, the pulley isn't moving on the shaft. The shaft is moving out of the cap.

Thanks for the suggestions.

John

 

[Dave_1962]

It's not a pulley - it's a drum.

 

[boreas]

It's not a pulley - it's a drum.

If we're talking about the ivory colored object in the photos, Onkyo calls it by the wrong name too.

John

 

[restorer-john]

They can do that, and it's painful to fix.

The shaft needs to be locktited to the spur gear, but you don't really want to pull it out (that's no fun putting them back). I've had many shafts that have slid out and ultimately needed securing.

 

[boreas]

They can do that, and it's painful to fix.

Thanks, John.

The shaft needs to be locktited to the spur gear, but you don't really want to pull it out (that's no fun putting them back). I've had many shafts that have slid out and ultimately needed securing.

I thought of that and decided that I should save it as a last resort since I've already had the shaft out and then had to figure out how to put the spur gear and stop ring back together. But it seems to me that the Loctite has to go inside the spur gear so that only the shaft is Loctited to the gear.

John

 

[restorer-john]

Yes, if the gear and spring loaded anti-backlash gear are out, you need to get it all back in first- there is a thread on AK just recently about these wretched gears.

Once you have it back in, and it gives the full range of tuner cap movement correctly (one tooth out makes all the difference), then you could conceivably slide the shaft out a small amount, just enough to get a few drops on the shaft, but none on the bearing (!). It's fiddly but doable- I've done many over the years.

You can also stand the receiver on its side with the tuning cap down and the pulley/drum up. Get everything in place and working first. Then use a tiny drop of super glue in a syringe and let it seep into the spur gear/shaft as the needle will fit in between the tiny gap. (you only get one go at it- the syringe needle blocks in a few seconds)

I've often thought an easier way would be a spring steel 'keeper' that pressed against the drum shaft centre from the other side...

 

[sKiZo]

Don't suppose there's a lock washer or spring clip that's worked loose or gone away on the other end of the shaft?

 

[boreas]

I've got it all back together and working and, by standing the tuner on its side as you describe, am able to pull the shaft out but I see no way whatsoever to apply Loctite to the shaft without getting it on the bearing and on the "stop ring" for the spur gear. There's no space between the spur gear/stop ring stack and the bearing.

John

 

[boreas]

Don't suppose there's a lock washer or spring clip that's worked loose or gone away on the other end of the shaft?

You'd think so, wouldn't you? But no, the drum/pulley is unsecured. I've seen this before so it's at least common if not universal.

John

 

[restorer-john]

Bugger. The rotating stop plates are getting in the way huh?

What about the other side? The gap between the frame and the spur gear? It doesn't sit in a bearing- you could put a few tiny drops on the shaft, then slide it out enough to take the lock-tite inside and then push it back- clean off any excess you don't want?

 

[boreas]

Bugger. The rotating stop plates are getting in the way huh?

What about the other side? The gap between the frame and the spur gear? It doesn't sit in a bearing- you could put a few tiny drops on the shaft, then slide it out enough to take the lock-tite inside and then push it back- clean off any excess you don't want?

That's what I've decided to try. I've already tried taking some tension off the dial cord. That didn't work.

I think I'll try Super Glue since it has good tensile strength to hold the shaft in the spur gear but not so good shear strength so, if the shaft ends up glued to the bearing, I can probably break it loose by turning the drum.

Thanks for the suggestions.

John

 

[restorer-john]

If they'd considered this issue in the first place, there was probably just enough room to have a tiny grub screw in the unmeshed part of the teeth- up against the skirt. It could have locked the shaft firmly.

Good luck with the super glue.

John

 

[boreas]

If they'd considered this issue in the first place, there was probably just enough room to have a tiny grub screw in the unmeshed part of the teeth- up against the skirt. It could have locked the shaft firmly.

Good luck with the super glue.

John

Thanks. I need to get some more Super Glue (mine dried out) and a syringe.

John

 

[Dave_1962]

 

[boreas]

Okay, well I got impatient and, rather than go out for Super Glue and a syringe, I decided to use JB Quick epoxy. I removed the drum and shaft and then the spur gear and stop plate. Then I spread a dab of epoxy evenly in the hole in the spur gear. Then, as quickly as I could, I reassembled everything and waited the the epoxy to set up.

It didn't work. The shaft is too tight a fit in the gear and the epoxy is too thick so all the epoxy got pushed out of the gear. There wasn't enough epoxy left in the gear to hold the shaft in place.

I guess I'll have to try the super glue tomorrow.

John

 

[RxDx]

Might work to serrate the shaft. Maybe vise grips offer enough leverage
to make some teeth marks that would hold the gear in place.

 

[sKiZo]

Depending how handy and ambitious you are, might want to try removing the pulley and drilling a small hole halfway across the shaft and bearing, then gluing a wire in using the epoxy, sort of like a standard "keyway" ...

Should be easy if you have a dremel tool available. Bonus points if you taper the wire so it locks in place without the glue ...

 

[boreas]

Might work to serrate the shaft. Maybe vise grips offer enough leverage
to make some teeth marks that would hold the gear in place.

I thought of that and may end up doing it. The problem would be in making it too rough to be reinserted as well as leaving the bottom 3mm or so un-knurled so that it would spin freely in the pilot bearing.

John