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SL-QL 15 track detection

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SL-QL 15 track detection

Postby ariendj » 07 Jul 2018 14:59

Just picked up a Technics SL-QL15 linear tracker. It looks quite good and playback works. I had a Grundig PS 6000 before (rebadged SL-DL5) and it's a nice upgrade.

I mounted my Audio Technica 102EP with the ATN 440MLb needle (thank you VinylEngine!) and the sound is excellent. What worries me though is that the track detection does not work. I read that when the detection fails it is possible that the QL15 will drop the needle at the starting position for 12" records, no matter what record size is actually on the platter. As I also have 7" singles I like to play I am afraid that this might happen to me and that I'd ruin the lovely ATN 440MLb.

This brings me to my question: How do I go about fixing the track detection? Where do I start? As much as I want to fix this deck I really do not want to ruin it by doing something stupid.

I have a soldering station, the service manual for the turntable and a cheap T4P cart for testing purposes. I did some minor repairs on the Grundig before (replaced some switches).

Any Help is much appreciated!
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ariendj
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Re: SL-QL 15 track detection

Postby fscl » 10 Jul 2018 16:15

A few easy things to try first. Remove the tonearm drive cover to reveal the tonearm drive system. IIRC, there should be an LED eye that travels / scans the platter looking for evidence of plastic, it's size and spacing locations. The eye moves in a slot counter to the travels of the tonearm, ie tonearm moves inward, the eye move outward.....:-k.

Clean the eye as it's exposed with the cover removed. Look at the wiring from the eye to make sure it's all intact. Try cleaning / cycling the sensitivity switch.

After cleaning and before committing to the 45, you can try programming selections on a regular 12" LP. Pick an older LP with larger song spacings. If it all works proceed below.

You can try and see if everything's working by putting a clear / colored 12" LP under a regular black 45 with adapter and pushing Start. If it all works properly, it will scan the platter think / cannot see the clear / colored LP travel to the 45 lead in groove switch speed and start to play....... [-o< [-o<

If you don't have a 12" that is non detectable by the turntable. Just use a 45 and press play. The tonearm will scan and detect and hopefully cue to the 45 lead in..... [-o< =D> =D>

If it looks like it will cue at a 12" lead in, then quickly lift the dust cover before the tonearm cues down on the rubber platter. The tonearm will immediately cue back up and move right over to the rest position. Unless your cueing silicone dampening fluid is completely dried out, you will have time to prevent the styli from touching the platter.

Hopefully the cleaning of the eye and sensitivity switch will solve the QL15 automatic cueing capability.

If not then, study the detection circuit and see / find component that's out of spec.

Good luck

Fred
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Re: SL-QL 15 track detection

Postby ariendj » 19 Jul 2018 21:41

Thank you fscl!

Please excuse my late reply. I took the turntable apart last weekend. First I cleaned the track sensor. Then, with the top cover removed it didn't play correctly as the needle could barely reach the record. I put my hand on top of the linear tracking mechanism to add some weight and lo and behold: not only did it play but the track detection also worked. I then confirmed that the IR diode is okay by fooling the 'lid closed' detector and having a look at the sensor with my phone camera.

There are controls for sensor gain and sensor resolution on the back. I'll try to increase the sensor gain a little this weekend, maybe that's what does the trick.

As soon as the track detection works with the lid closed I'll mount my 'testing cart' and try out fscl's trick with the transparent record underneath the 7". Great idea by the way. Turns out that my transparent red copy of 'Strawberry Letter 23' is more useful than I though ;)

In the mean time I ordered some teflon grease and some bearing oil that will hopefully arrive before the weekend. I'll remove all the grease from the linear tracking mechanism and apply some fresh grease. The tonearm doesn't exactly glide across the rail right now. It looks more like it's being dragged along...

The belt also needs replacing as it has gone egg-shaped. For now it will have to do though as I need to get hold of an 18mm belt. I still have lots of 20mm belts but they are just that little bit too large.

I'm not quite sure about the bearing oil. I bought some sewing machine oil as it was reasonably priced (2€/100ml) and I have read that it will work as a replacement for Technics bearing oil. I found some Panasonic oil on amazon but at 10€/10ml I felt it was kind of a rip-off.

What's the best way of going about an oil change? Should I try and remove all the oil from the bearing and replace it with the sewing machine oil? Is there a way I can be sure that all the oil has been removed from the bearing?

Or can I just add a little oil until the bearing is full again? Would it make a difference that I'm using two different kinds of oil?

Thank you as always!
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