Dual 701 repair

[alfonsol]

Hi,
i got, a dual 701 that need some repairs.

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tonearm removed

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1- Lift cam P/N 227 048 is broken
2- tonearm was loose, at first i thought i needed a new tonearm, but when i dissassembled it i discovered that someone tried to change the wiring and didn't know how to reasemble properly the tonearm. in fact tonearm is in very good shape, but the wiring is cut.

Tonearm and first attempt to rewire it

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3- counerweight is broken inside.

counterweight dissassembled

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4- headshell is missing.

Questions:

1- Where i can get cable to rewire the tonearm? I tried wires from a vga cable, but i think they are too rigid.

2- the service manual shows 4 cables in the toneam wiring. in fact they are 2, but shielded. My tonearm has 5 wires. the 4 wires for the left and right channels. and another wire(black) connected to the center contact of the headshell. in the pictures you can see this cable.

[alfonsol]

oops, submitted before finishing the post

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Also the center contact is connected to the tonearm itself.
Do you know if this black cable is supposed to be here or not?

3- Where i can get a counterweight?

4- where i can get the lift cam?

[Alec124c41]

You can use the thin, flexible wires from an old USB or older computer mouse.
The 5th black wire is a ground wire.

Cheers,
Alec

[alfonsol]

Thank you Alec124c41
The black wire is supposed to be here?
in the schematic i see the center pin connected to the right channel ground

[alfonsol]

I rewired and assembled the tonearm. beeraings are tight and smooth, i think i'ts ok. i am waiting for the headshell to test it.

i dissassembled the couterweight, the leaf spring is broken, and the rubber parts are in bad shape. i am looking the way to make a new leaf spring. i will try to replace the rubber parts with silicone.

also i am waiting for the 0,047uf cap in the power supply. i will change it before it fails.

should i replace the electrolytics in the motor? i'm worried about that, because i don't want to mess with the motor.

[3rd_Ear]

should i replace the electrolytics in the motor? i'm worried about that, because i don't want to mess with the motor.

I've got myself some oldtime-radios from the 1950's, one from about 1949, where the electrolytic capacitors are still fully functional.

On the other hand, one or another of some younger devices of mine had electrolytics, which did not function after only about 20 years of service.

As with books, you shouldn't/can't judge them by the age.

So, just try it out.

[alfonsol]

Thank you 3rd_ear
i made avisual inspection of caps and the only suspect cap was the 0,047u cap that was cracked. i replaced it and tried the turntable.
it runs with steady speed and the strobe works. the motor is very silent.

Also i rewired the tonearm. before i try the wiring i have to fix the counterweight and put a cartridge, but i measured the wiring with my DMM and it's fine.

I want to find a new counterweight, but did't found one yet. Also i am trying to find a leaf spring to replace the leaf sping in my counterweight, but didn't found one.

Also i need the lift cam(the little plastic piece in the cue lever), and did't founnd one yet.

[alfonsol]

I "repaired" the counterweight. i removed what's left of the leaf spring. The counterweight have 2 counterweights insisde. a little one suspended only by rubber, and a big one suspended with the leaf spring and a rubber. The rubber that suspended the little counterweight was in good shape, but too soft to hold the 2 counterweight, so i removed it(and put it in a safe place) and replaced with silicone. then i secured the big counterweight to the cage with the screw in the rear. The glued the counterweight to put all in place, but made sure i can dissassemble it again if i got a new leaf spring.
The result is similar to the counterweight on other dual turntables.

I put a AT440mla and tried the turntable. I got sound in both channels, and good tracking. The only problem is the sound is too bright and a little hum and hiss, but i think the culprit is my cheap preamp. I searched reviews of my preamp, and other people got the same results with it.

auto stop sometimes works ok, but other times the tonearm reaches the rest position and lowers, then the turntable shuts off, and then it powers on again, raises the tonearm, and repeat the stop cycle, and then shuts of again. this is an infinite loop until i unplug the turntable and make the platter spin backwards and that sometimes reset the mechanism.

same behaviour with auto start. instead of enter the start cycle it enters the stop cycle in an infinite loop. sometimes when i just reseted the mechanism it works fine once.

[gridleakrick]

alfonsol,
Do not spin the platter backwards! On some turntables you can permanently damage the mechanism.
On Dual turntables, the most common cause of arm movement problems is caused by a bad "guide" (also known as the pimple or steuerpimple). This is a small plastic cap which fits on the end of a pin under the base of the tonearm. Download the service manual here at this website for your turntable. Look at item number 167 on pages 14 and 22. Also, do a search on this website for steuerpimple in the "google custom search" box in the top, right hand corner of the page. You will find all the information you need to know on how to replace it and what with.
Good luck and let us now how it turns out.
Rick

[alfonsol]

Thanks glideacrick.

The steuerpimpel works ok, i already changed it.
it's the mechanism that don't work as it should.
when it should enter the start cycle, usually enters the stop cycle, even if the tonearm is at rest position, i can see the steuerpimpel trying to move the arm to the rest position.
when it enters the stop cycle it repeates again , and again, and again.....
switching off and on the turntable.

[mrow2]

Cycle problems are mainly a matter of determining what is causing it to repeat-trip or not cycle off, usually something just slightly out of alignment. Don't mess with that motor or power it unless everything is in place as if it was being used. Don't touch the VR adjustments or caps unless you have no choice but to do so. This is not an elegant design, way too many VRs and best thing is to leave it alone if it works.

[alfonsol]

Thanks mrow2

The motor work ok, so i don't plan to mess with it.
The only cap i changed is the 0,047 cap in the power supply because it was cracked and i don't wanted to turn on the turntable only so see smoke.

i thin i narrowed the problem on the auto function. i got the auto stop working. after cycling several times the mechanism to see how it works, the auto stop started to work properly. i think parts 122 and 123 in the SM where dirty and i kinda loosened them when i moved the mechanism so many times
Auto start does,t work because PAWL (part 146) doesn't engage. or sometimes engages, but not disengages after start cycle.

I will clean it all, but i will wait the lube kit i ordered, so hopefuuly i only have to remove the cam wheel once.

Do you have any pictures of how it should look behind the cam wheel?

[alfonsol]

PIctures of how it looks now

[alfonsol]

Finally i received the lube kit and i lubed the turntable.
now the automatic functions work as it should.
the mechanism was stuck with old grease
Now my only realissue is the lift cam for the manual cue.