Dual resources (getting started with repairs)

[doodahman]

View media item 21027Hi, I know there's large presence here of Dual enthusiasts.

I just picked up my first Dual -- a 1242. Not the most collectible, but hey, it was free! I did some electronics hobby work back in the day (40 years ago), so I at least know a capacitor from a resistor. I'm looking forward to diving into the turntable and getting it in good running condition.

I was hoping to find some online resources - I downloaded the service manual from vinylengine. But is there anything else? I'm not sure where to start, other than maybe lubricating and cleaning.

The unit powers on and has sound... But it runs slightly slow when set to 33-1/3 and really slow at 45... I'm not sure the speed selector actually does anything.

And the pitch control also doesn't seem to have any effect.

Any tips would be appreciated!
View media item 21028

 

[NoTransistors]

Resistor
Not resister

The motor pulley is sectioned into four or so wedges. To modify pitch, a tapered dowel is drawn into it which will alter the diameter and therefore the pitch. Either the tapered dowel is stuck because of belt dust and corrosion or a toothed belt which links the pitch knob to a little gear on the pitch assembly is busted
The toothed belt is actually still available
You might want to disassemble the motor while you are in there and oil the bushings with any one of several non-teflon non graphite motor lubes discussed in previous threads
I use plain car engine oil

 

[doodahman]

Resistor
Not resister

Argh. Ha. Guess I was thinking of the draft.

The motor pulley is sectioned into four or so wedges. To modify pitch, a tapered dowel is drawn into it which will alter the diameter and therefore the pitch. Either the tapered dowel is stuck because of belt dust and corrosion or a toothed belt which links the pitch knob to a little gear on the pitch assembly is busted
The toothed belt is actually still available
You might want to disassemble the motor while you are in there and oil the bushings with any one of several non-teflon non graphite motor lubes discussed in previous threads
I use plain car engine oil

Thanks so much. I ordered a belt, but it's the main flat belt. I didn't realize (or notice from the parts diagram) that there was a second, toothed one.

So, how freely should the speed-selector move? i.e., how easily can you switch from one speed to another? Right now it's stiff - not stuck, but stiff.
Similarly, what does the pitch control feel like as you change it? Does it move freely? Does it stop when you get to a certain point?
This one moves freely to a point and then it clicks. I'm wondering if that's right or if it should come to a full stop where you can't turn it further.

 

[NoTransistors]

I have nothing here to compare as most of my repairs are Dual idlers and a few direct-drives.
Wait 'till the rest of the world wakes up. Someone will reply

 

[olddude55]

Argh. Ha. Guess I was thinking of the draft.



Thanks so much. I ordered a belt, but it's the main flat belt. I didn't realize (or notice from the parts diagram) that there was a second, toothed one.

So, how freely should the speed-selector move? i.e., how easily can you switch from one speed to another? Right now it's stiff - not stuck, but stiff.
Similarly, what does the pitch control feel like as you change it? Does it move freely? Does it stop when you get to a certain point?
This one moves freely to a point and then it clicks. I'm wondering if that's right or if it should come to a full stop where you can't turn it further.

A friend of mine had a 510 belt drive. He had some problems with the cartridge sled and I fixed it for him.
The pitch control moved freely but had no effect, so it's likely the belt was already broken. I didn't know enough about the unit to check, all I did was clean the sled contacts. The speed control lever moved easily as well.
This was a unit that got infrequent use, but just enough to keep everything from freezing up.

 

[doodahman]

To modify pitch, a tapered dowel is drawn into it which will alter the diameter and therefore the pitch. Either the tapered dowel is stuck because of belt dust...

The toothed belt seems intact. When I turn the pitch control, the belt moves and the toothed gear/sprocket under the platter moves with it. In other words, the sprockets at both ends of the belt move in conjunction with the pitch knob.

I disassembled the motor... the rotor has a few rust spots. Is this primarily cosmetic? Should I worry about it?

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[doodahman]

So for what it's worth, the 1242 doesn't have a tapered dowel, at least not what I'd consider a dowel.

The toothed gear wheel has a little piece of plastic at the top which pushes up/down against a stationary piece of plastic above it. This causes a metal "abutment" plate to raise, lower, which pushes a tapered piece of metal into a sleeve that expands or contracts, changing diameter and thus the speed

View media item 21038View media item 21040View media item 21039

 

[NoTransistors]

What is the difference between a tapered dowel and your description?
However you want to describe the parts, the wedge must move up or down with the top adjuster plate. Do not squeeze the pulley sections as they easily deform. Pull out the wedge and clean everything.