Picked up a Dual 1245 yesterday and can't get the pitch control to have any effect on speed. It runs fast at both speeds. The control is connected by a toothed belt to a toothed pulley which it rotates, but for the life of me I can't see how this is suppose to effect the platter speed. Anyone have any ideas?

Mike

That tiny belt does break. Are you certain that it is turning the gear at the motor? I seem to recall that the way it works, is by raising and lowering the top motor spindle support bracket. This forces a spacer down into the pulley. Why? Because the pulley is segmented like an orange, and by forcing the sections further apart, the pulley gets fatter, thereby altering pitch.

Seth
Forever Analog

Seth is right about the belt. Lift off the platter & you'll see it beneath the motor pulley. If it's missing, there's another fix. You need a 5.5 MM nut driver On top of the pulley is that 5.5 MM nut, probably with blue lock tite on it. A little turn counter clockwise will slow it down. Trial and error here.

bill@fixmydual.com

the belt is intact and moving the toothed pulley. I have moved the hex nut both directions and at has no effect. Should I remove the hex nut and disaasemble to see if something is frozen?

Mike

You need to see whether the segmented motor pulley is expanding and contracting or not, by seeing if the spaces between the segments change their gaps, Mike. It won't be much, but it can be seen.
Here's a blowup of the pulley assembly.
Tom

Nice pic!

#15 is the motor pulley. I wouldn't go adjusting that. The placement on the motor output shaft is a pretty close tolerance. That's so the belt stays on the platter on both speeds.

BUT, on top of the motor pulley (#15) is an insert that moves up and down when you adjust the pitch (not separately numbered). This insert makes contact with the top mounting boss, and when you speed up the pitch, the pulley moves up, the insert has contact with the boss, forcing it down into the pulley, expanding the pulley, increasing the speed. Likewise, when you slow it down, the pulley goes down, a spring underneath the insert pushes it up, making the diameter of the pulley smaller and slowing it down. Put it on full slow pitch. See if the insert (chrome in color) is making contact with the mounting boss. if not, it's frozen in the pulley. A LIGHT TAP (I know how much Seth likes hammers) on the chrome insert with a small block of wood should free it up. No oil or WD-40 - it'll get on the belt!!

bill@fixmydual.com

I have spare pulleys if it comes to that.

I've hammered on it on the motor pulley and played with the nut on the toothed pulley. I see some movement of the motor pulley, but it still doesn't seem to do anything. If I run the nut on the toothed pulley all the way down it will slow it down on 33.3, but it never becomes steady and there doesn't seem to be any fine control with using this method. None of this had any discernable effect on 45. Its still runs fast. Is there something on the underside that I should check? If so how do you get it free of the base? It seems that the suspension springs won't let it go.

Mike

Get professional help.

Not worth it to me. It's landfill food.

Mike

This is an easy problem to solve, for the mechanically inclined.

The vario-pulley is expanded (to go faster) or contracted (to go slower) by a conical plug that moves up and down inside the pulley. The plug's height (and thus the speed) is controlled by a thrust plate that contacts the plug. Changing the speed control moves the thrust plate up and down.

The standard failure is just that the plug assembly gets sticky on the motor rotor shaft it rides up and down on. Exercising extreme care, take the whole mechanism apart. Using q-tips and solvent, remove any hardened grease from the shaft and inside of the plug.

It is often useful to take #1000 or finer sandpaper and resurface the shaft, and to take a "curl" of sandpaper to the inside of the plug.

Once these steps are done and any metal glaze cleaned off, the plug should move up and down freely on its shaft. Thus, the thrust plate can once again take control of the plug and allow the vario-pulley to expand and contract as needed.

Note that even if the speed adjustment belt is broken, there is a hexnut -- accessible through a hole in the platter -- that you can use to adjust the "baseline" vario-pulley expansion to 33-1/3 exactly.

I've done the above procedure hundreds of times over the last 25+ years. It works evey time.

Best,

Fred Longworth

deleted

Before you landfill it, pull the motor. It has the SM-860. That motor replaced the SM-840 found on 601's and 1249's. The 840 at 60 Hz will intermittantly spin the platter at double speed. No fix but to change the motor.

Throw it on the 'bay as a 601 & 1249 fixer. I have yet to see a 840 motor that doesn't act up.

This is an easy problem to solve, for the mechanically inclined.

The vario-pulley is expanded (to go faster) or contracted (to go slower) by a conical plug that moves up and down inside the pulley. The plug's height (and thus the speed) is controlled by a thrust plate that contacts the plug. Changing the speed control moves the thrust plate up and down.

The standard failure is just that the plug assembly gets sticky on the motor rotor shaft it rides up and down on. Exercising extreme care, take the whole mechanism apart. Using q-tips and solvent, remove any hardened grease from the shaft and inside of the plug.

It is often useful to take #1000 or finer sandpaper and resurface the shaft, and to take a "curl" of sandpaper to the inside of the plug.

Once these steps are done and any metal glaze cleaned off, the plug should move up and down freely on its shaft. Thus, the thrust plate can once again take control of the plug and allow the vario-pulley to expand and contract as needed.

Note that even if the speed adjustment belt is broken, there is a hexnut -- accessible through a hole in the platter -- that you can use to adjust the "baseline" vario-pulley expansion to 33-1/3 exactly.

I've done the above procedure hundreds of times over the last 25+ years. It works evey time.

Best,

Fred Longworth

Tried the cleaning routine. There was a build-up on the shaft, which I polished off, but it doesn't seem to make any difference. If I really crank down on the hex nut I can get 33.3 close, but 45 is a lost cause. Any other thoughts as to what to try before it gets recycled?

Mike

Barring your repair of it, what would it take for you to ship it to Peoria, IL 61606 wrather than pitching it?

But will it Play in Peoria??


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