Sl-7 Disassembly Problem

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fscl
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Re: Sl-7 Disassembly Problem

Post by fscl » 05 Oct 2014 16:20

This is the main weakness / complaint of the cover supported / suspended tonearm drive system, the potential for noise transmission into the music reproduction chain.

In my obsession of Technics tangential players (first a SL-7 that became dodgy), I've come across many in various states of repair / disarray. Some drives are / have been restored to silence, there's a QL-1 bought for parts that now plays perfectly but has the annoying thumping when traveling quickly ie run out groove to the center label and high speed left / right cue to songs. Not audible tracking music though.

On these units fresh rubber..... :oops: is your best friend. New, plump, fat, resilient rubber helps to isolate vibration and noise from the tonearm and cartridge. As these parts are no longer available, I've resorted to rubber restorer to renew.

In taking apart and reassembling these tangentials, I've come across critical rubber that should / does deaden drive vibration.

1. O-ring belts. If these are too tight, the vibrations in the drive motor will leak through as described by Dave iG above.
2. Drive motor rubber cushioning. There is usually a rubber jacket / rubber piece that surrounds the drive motor and is then clamped to the upper cover. I've found loosening the clamp, readjusting the rubber jacket / rubber isolater and cinching the clamp just tight helps in reducing vibration transmission.
3. Hand in hand with this is to lubricate the tonearm drive motor shaft and drive the tonearm drive motor in both directions for a while with a battery as described above. The smoother this motor turns the less the vibration. The motor is designed to turn in both directions and some high speeding will turn in brushes and commutators.
4. Tonearm guide rod bushings. I've found these to be totally flattened and distorted by the clamps that secure the guide rod. With the use of rubber restorer, they've plumped up like the PL-12 motor mount bushings. Once again clamping these rubber guide bushings at the ends of the guide rods just tight allows the rubber to dampen motor vibrations and lessen vibration traveling through the rod to the tonearm.
5. Re-greasing (very sparingly) the worm and spur gears with a modern grease that won't thicken and remains in it's original viscous state dampens vibrations. Though I do not like regreasing the guide rod (as it's exposed and can attract dirt and dust) you can try using a light PTFE grease as dampening.

HTH, good luck.

Fred

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 05 Oct 2014 16:47

might get some rubber restorer myself and give everything a quick spray.. before it becomes a problem!

fscl
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Re: Sl-7 Disassembly Problem

Post by fscl » 05 Oct 2014 16:52

healthyhouse wrote:Well, you are right, i forgot about the 2 speeds (via cueing).
So, during my explorations, a new problem. The brass pulley became loose and won't turn the worm gear. this also happened right after I got it but i was able to "pop" the pulley back on the end of the chrome rod (or axel). it stayed put ...........snippage...........
Any ideas if this is correct?
Never had problems with any of the pulley wheels falling off. I've taken a look at page 8 and the link to the SL-10 pictures VE member monoethylene has contributed. None of the pictures of pulleys show any glue, I believe the pulleys are held in via slightly undersized centers of washers that "slip and snap" onto the pulley guide shafts. Kind of like the infamous Sankyo drive tire / tyre (for you in UK :D ) pulley on Naks. If these washers no longer friction fit and hold the pulleys, I'm sure you can use something like red nail polish..... etc....

Good luck

Fred

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Re: Sl-7 Disassembly Problem

Post by knube2 » 15 Nov 2014 21:22

Hello

Please be kind as this is my first post, I have been following all the great advice on this site regarding the SL-DL1 and have performed open heart surgery and cleaned and re lubricated the tone arm as described and fitted a new belt, I only have one other problem i need to try and sort out, when playing a 45 the strobe light is rock steady and the adjustment wheel is about in the center, however when i'am playing a 33 the adjustment wheel is fully clockwise and the strobe segments are still slowly moving to the right so i have no more adjustment, I have used switch cleaner on the pot and connections but this has made no difference,I see on the main PCB VR101 and VR102 but cannot find any reference to them, is it possible these could be for adjusting the base setting of the TT speed.

Any advise would be greatly apresiated

analogaudio
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Re: Sl-7 Disassembly Problem

Post by analogaudio » 15 Nov 2014 21:44

Welcome to VE :-)

Check the library here for a copy of the service manual for your model, or a close equivalent model. It is very likely that the two trimmers you mention are used for coarse adjustment of speed, so that "normal" is found with the fine wheel in center position approximately. I have successfully made this adjustment on another Technics model for the same reason, simple and straightforward :-)

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Re: Sl-7 Disassembly Problem

Post by knube2 » 16 Nov 2014 17:44

Thank you for the welcome.

Had a good search through all the documents on this site and found one with a reference to two VR's, 101 (33) and 102 (45) for adjusting the speed,although they were not on the main PCB like the SL_DL1 but I thought that being built by the same company and there attention to detail I would give it a go, before I made any adjustments I marked there existing position with tipex so i could go back, as in the other documentation is referred to VR101 for the 33 I started with this one as I only had a problem with this, turned it anti clock wise, this had the effect of slowing the TT down and I needed to go faster so another three attempts in the opposite direction and it is now spot on with the fine adjustment wheel in the center, I did have to turn it further that I thought 5-6mm, as to the VR102 I can only assume it is for the 45 adjustment but as mine was ok I left it alone.

Another resurrected SL-DL1 running like dream and hope fully for many a year to come.

Once again thank you for all the useful information from the dedicated people on this site sharing there knowledge.

fscl
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Re: Sl-7 Disassembly Problem

Post by fscl » 20 Jan 2015 15:22

Thanks to LmMk2 for main PCB removal:

viewtopic.php?f=16&t=74336&p=599777#p599777

Fred

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Re: Sl-7 Disassembly Problem

Post by Kota62 » 23 Feb 2015 03:22

I bought my SL-7 in October of '81 at RAF Bentwaters (UK), my first assignment in the Air Force, used it continually til about 15 years ago when it went into storage due to the convenience of the digital age... Pulled it out of storage recently & thanks to the terrific folks here, diagnosed & repaired the frozen tone arm motor.
Can't tell you what a pleasure it is to spin vinyl again. we have a 2nd & Charles here who carry old records for a couple of buck a piece, loads of fun flipping through records again.
Cheers
Gary
BTW: found the original receipt, paid $261.00 :)

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 28 Mar 2015 19:07

had a bit of a brown trouser moment with my sl7 a few days back,was playing fine then the arm decided to scrape across the record,not good for my ears..or my sanity,im getting sick of fixing this bloody thing!!

so had a quick poke around and found this... oh dear.

32232

turns out normal trim pots wont do,as technics decided to mount these backwards,so i needed some that could be adjusted from behind as well,and be vertical.. no problem i thought,i was wrong!

after a bit of searching i found some from mallinson electrical over in good old yorkshire,they confirmed that these could be adjusted from the back,1 day later they arrived!

fitted tonight and all is well,bit snug shoving them on the servo adjust board,so i put some tape behind the old cut trimmer cover so it wouldnt short on the case

32233

after messing round readjusting it i settled on 1/5th to the left of where it is on that pic.

just hope the damn thing gives me a break for a while now!

fscl
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Re: Sl-7 Disassembly Problem

Post by fscl » 29 Mar 2015 06:12

lnsmnMkII,

Just to clarify your post, the SL-7 tone arm solenoid malfunctioned and didn't lift the tonearm before traveling left or right and resulting in a blood curdling zzzzzzziiiiippppp across the grooves..... #-o ](*,)

What pots were adjusted to make the tonearm lift up off the grooves..... :-k :-k

Or was the logic faulty in not controlling the tonearm correctly..... :-k :-k

Fred

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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 29 Mar 2015 13:17

yes fred it was the servo adjusters at the back,vr302 was a bit rusty and the back decided to fall off causing the logic to think the tonearm wasnt straight,and decided to try and keep correcting;by dragging the arm across the record.

you can mimic the same thing by turning vr302 just over 3 quarters to the right (looking at the deck from the front),if you do it slowly you'll see the arm slew over to the left while playing then it'll just start dragging itself over the record.

got lucky this time,no damage to the record i was playing or the stylus,glad these things are light trackers!

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Re: Sl-7 Disassembly Problem

Post by Skauneboy » 06 May 2015 17:17

On my Technics SL-10 the thing that finally got rid of the "thump problem" was to grease the tone arm guide rod. I had originally used dry teflon lube but replaced it with a more viscous teflon grease which seems to dampen the vibrations from the servo motor perfectly. Worth a shot if you, like me, can't get rid of that low frequency thump no matter what you try.

The one annoyance left to fix on my SL-10 is to tune the return position on 12" LP's. On a few LP's the tone arm returns before it has reached the run-out grooves. In the service manual the only adjustment mentioned for the tone arm return is the micro switch one. I've found that this mechanism is only engaged when I play 7" records and that 12" playback seems to rely on some kind of non-mechanical detection. Anyone figured this out?

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Re: Sl-7 Disassembly Problem

Post by Skauneboy » 08 May 2015 14:28

Ok, I think I've worked it out. When I got the TT the tone arm rope was broken so I replaced it with a dial cord which is slightly thinner than the original one. This obviously affects the distance the tone arm travels for each revolution that the servo motor turns. Something the motor logic of course doesn't care about. So the position for auto return on 30 cm records and start position for 25 and 17 cm records are slightly off.

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Re: Sl-7 Disassembly Problem

Post by warpig » 23 Jun 2015 06:00

Skauneboy wrote:Ok, I think I've worked it out. When I got the TT the tone arm rope was broken so I replaced it with a dial cord which is slightly thinner than the original one. This obviously affects the distance the tone arm travels for each revolution that the servo motor turns. Something the motor logic of course doesn't care about. So the position for auto return on 30 cm records and start position for 25 and 17 cm records are slightly off.
Hello
I have an SL7 that in some cases will lift before the end of the record. Did you fix this problem. I attempted to adjust the end switch S307 without any success. Bought it used but it may be the rope was replaced by a previous owner.
Thanks
greg

fscl
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Re: Sl-7 Disassembly Problem

Post by fscl » 10 Nov 2015 20:27

Distortion caused by dirty muting switch, thanks to ve7chk:

https://www.vinylengine.com/turntable_f ... 52#p672152

Fred

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