Technics SL-7 Arm drive problems - UK Vintage Radio Repair and Restoration Discussion Forum

'LIVEWIRE?' · 17th Feb 2017, 12:01 pm

Specifically that the brass pulley has come off the worm drive shaft, throwing off the small drive belt in the process, resulting in the linear tracking tone arm not moving. I haven't found any way to secure the pulley to the highly polished metal shaft (there's no provision for a circlip), so, does anyone have any suggestions as to how to do this, please?

sp10mk11 · 17th Feb 2017, 12:56 pm

If there is no locking screw etc, then I presume it is heated then pushed on, on the other hand if it slide on the motor shaft then a drop of super glue will hold it.
Beautiful deck by the way
Gary

ukcol · 17th Feb 2017, 1:37 pm

Quote:

Originally Posted by sp10mk11

........
Beautiful deck by the way...

Yes, Technics made some nice stuff. I recently worked on a pal's Technics SL-L20 which is also a linear tracking turntable. A new belt, new stylus and a clean & lubricate of the slide bar that the arm moves on was all that was needed to revive it. Unfortunately he wanted it back.

'LIVEWIRE?' · 17th Feb 2017, 1:48 pm

I tried superglue, Gary, but the pulley came off again, despite leaving the deck for several hours before I powered it up again. The surface of the shaft and the inside of the pulley are presumably too 'slippery for the glue to adhere properly.

'LIVEWIRE?' · 17th Feb 2017, 2:24 pm

It seems that there should be a stopper on the end of the worm drive shaft, to hold the pulley in plce.

TonyDuell · 17th Feb 2017, 9:37 pm

I assume the pulley is not large enough to drill/tap it for a grub screw.

What about one of the Loctite (or similar) anaerbic adhesives. I am pretty sure there was one designed to fix gears/pulleys to shafts (and they never come off again!). The normal threadlock is designed to come undone easily, but others aren't

'LIVEWIRE?' · 17th Feb 2017, 10:32 pm

It may be possible to drill the pulley boss to accept a grub screw, Tony, but I may see if an anaerbic adhesive will do the job first.

Michael Maurice · 18th Feb 2017, 4:14 pm

What I would do is slightly roughen the end of the shaft with some emery paper then use some JB Weld glue to fasten the pulley to the shaft.

TonyDuell · 18th Feb 2017, 5:03 pm

I've not tried it, but something like this :

http://uk.rs-online.com/web/p/retain...ounds/0693854/

might do it.

'LIVEWIRE?' · 18th Feb 2017, 5:20 pm

Thanks, Michael, for that suggestion. I may use emery paper on the shaft before refitting the pulley.

'LIVEWIRE?' · 10th Mar 2017, 11:29 pm

I've now refitted the pulley using epoxy resin, and hope it will stay in situ. and have also replaced the belt with one obtained from an eBay seller, which seems a little slack. However, despite carefully reassembling the arm drive mechanism, ensuring that it would wind to the RH end stop, the turntable doesn't even rotate. I suspect the cause to be that the microswitch at the RH end isn't closed, which means dismantling yet again to see what's happened.

17th Feb 2017, 12:01 pm	#1
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Technics SL-7 Arm drive problems Specifically that the brass pulley has come off the worm drive shaft, throwing off the small drive belt in the process, resulting in the linear tracking tone arm not moving. I haven't found any way to secure the pulley to the highly polished metal shaft (there's no provision for a circlip), so, does anyone have any suggestions as to how to do this, please?

17th Feb 2017, 12:56 pm	#2
sp10mk11 Octode Join Date: Feb 2009 Location: Cornwall, UK. Posts: 1,275	Re: Technics SL-7 Arm drive problems If there is no locking screw etc, then I presume it is heated then pushed on, on the other hand if it slide on the motor shaft then a drop of super glue will hold it. Beautiful deck by the way Gary

17th Feb 2017, 1:48 pm	#4
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Technics SL-7 Arm drive problems I tried superglue, Gary, but the pulley came off again, despite leaving the deck for several hours before I powered it up again. The surface of the shaft and the inside of the pulley are presumably too 'slippery for the glue to adhere properly.

17th Feb 2017, 2:24 pm	#5
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Technics SL-7 Arm drive problems It seems that there should be a stopper on the end of the worm drive shaft, to hold the pulley in plce.

17th Feb 2017, 9:37 pm	#6
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,225	Re: Technics SL-7 Arm drive problems I assume the pulley is not large enough to drill/tap it for a grub screw. What about one of the Loctite (or similar) anaerbic adhesives. I am pretty sure there was one designed to fix gears/pulleys to shafts (and they never come off again!). The normal threadlock is designed to come undone easily, but others aren't

17th Feb 2017, 10:32 pm	#7
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Technics SL-7 Arm drive problems It may be possible to drill the pulley boss to accept a grub screw, Tony, but I may see if an anaerbic adhesive will do the job first.

18th Feb 2017, 4:14 pm	#8
Michael Maurice Moderator Join Date: Feb 2006 Location: Wembley, Middlesex Posts: 7,230	Re: Technics SL-7 Arm drive problems What I would do is slightly roughen the end of the shaft with some emery paper then use some JB Weld glue to fasten the pulley to the shaft. __________________ Forum Moderator http://www.michaelmauricerepairs.co.uk/

18th Feb 2017, 5:03 pm	#9
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,225	Re: Technics SL-7 Arm drive problems I've not tried it, but something like this : http://uk.rs-online.com/web/p/retain...ounds/0693854/ might do it.

18th Feb 2017, 5:20 pm	#10
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Technics SL-7 Arm drive problems Thanks, Michael, for that suggestion. I may use emery paper on the shaft before refitting the pulley.

10th Mar 2017, 11:29 pm	#11
'LIVEWIRE?' Rest in Peace Join Date: Mar 2006 Location: N.W. Oxfordshire(Chipping Norton) Posts: 7,306	Re: Technics SL-7 Arm drive problems I've now refitted the pulley using epoxy resin, and hope it will stay in situ. and have also replaced the belt with one obtained from an eBay seller, which seems a little slack. However, despite carefully reassembling the arm drive mechanism, ensuring that it would wind to the RH end stop, the turntable doesn't even rotate. I suspect the cause to be that the microswitch at the RH end isn't closed, which means dismantling yet again to see what's happened.