Sl-7 Disassembly Problem

[fscl]

DiGreen experiences:

I can even hear a small click from the rear of the SL-7 as if a swtich is responding but perhaps not making complete contact. It does seem to be working more often the more I use it, so maybe that will come back with use. I may also trace down the switch and try cleaning it.

The worse problem is that the tonearm will usually not advance at all when I play a record. Since it does advance occasionally, it does have all the symptoms of a dirty sensor or something out of spec. I just looked through the service manual and couldn't find a reference to the location of the offset sensor.

First try displacing the tonearm through it's full range of movement a few times with the power and the tonearm lock / safety off. Then exercise <<>>, in-out, in-out... etc....as it seems to be getting better. I also try to clean the related plug in connectors on the pcbs

I was looking at page 12 of the Service Manual "Adjustment" section and in particular "Offset adjustment of tonearm and servo gain" section and read through and follow the instructions on page 13 and 14, Steps 2, 3 and 4. Hopefully this will cure the skip problem while the tonearm tracks an LP.

Offset angle detect sensor is an LED / Sensor combination, @ PC 401 on the IC 301 block diagram. I believe this optical sensor is located in the tonearm support well opposite to where the hex wrench is inserted to adjust the centering voltage. You may want to gingerly "blast" some air in this well where the "T" goes into the tonearm support and dislodge any dust / dirt prior to centering adjustment voltage. (ie a turkey baster or something that can push some air quickly and semi forcefully, I think new canned air may be a little too strong unless you've got a "low" canned air bottle).

After displacing and moving the tonearm and application of air, try playing a record again. You may have cleaned the sensor to bring the fine tonearm movement back. If not continue with voltage measurements and adjustments according to steps 3 and 4. A 1 mm test LP will be difficult to find, however, I believe you can use a standard LP for adjustment of the voltages. You really want the voltages correct while moving across one of the vinyls in your collection.

Good luck. Hopefully this will get you spinnin', trackin' and postin' in Currently Playing....

Fred and refer to page 30 for the tonearm connections to clean leading into the pcb, 111 for audio signal and 110 for tonearm drive.....

[Dave in Green]

fscl, again, this is just fantastic advice. I really appreciate the time and effort that you and others are taking to help me. I'll reference the Service Manual again and try to follow all of the steps that you outlined.

I actually already did a few things you suggested before reading your last post, as I had guessed they might be helpful. I displaced the tonearm through it's full range of movement many times, and blew a few quick puffs of air into the opening where the "T" goes into the tonearm support. I had guessed that the sensor was in there and might be covered with dust.

I also continued exercising the <<>> buttons. As I previously mentioned, the full speed tonearm advance and reverse worked flawlessly from the moment I changed the belt. The 1/2 speed was intermittent but constantly improving, and by the end of the last session was working almost 100% of the time.

The automatic tonearm advance during play was the slowest to respond. It went from not advancing at all to advancing a few big steps and stopping. When I saw that the tonearm was not advancing, I'd just hit the cue button to avoid excessive wear on my vinyl, exercise the 1/2 speed advance manually and start playing another track.

Gradually the automatic tonearm advance began to take smaller and more frequent steps. Finally, the last album I put on played through an entire side with the automatic advance working absolutely flawlessly with many small, consistent steps and not a single skip. Based on this, I have to believe that the voltages are probably not far out of spec.

Even though it appears to be working really well right now, I'm sure that it will benefit from cleaning all connectors and checking voltages. I'll continue to post my experiences in this thread as a reference to anyone else who may try to revive an SL-7 in the future.

[flavio81]

The automatic tonearm advance during play was the slowest to respond. It went from not advancing at all to advancing a few big steps and stopping. When I saw that the tonearm was not advancing, I'd just hit the cue button to avoid excessive wear on my vinyl, exercise the 1/2 speed advance manually and start playing another track.

Gradually the automatic tonearm advance began to take smaller and more frequent steps. Finally, the last album I put on played through an entire side with the automatic advance working absolutely flawlessly with many small, consistent steps and not a single skip. Based on this, I have to believe that the voltages are probably not far out of spec.

Even though it appears to be working really well right now, I'm sure that it will benefit from cleaning all connectors and checking voltages. I'll continue to post my experiences in this thread as a reference to anyone else who may try to revive an SL-7 in the future.

Don't move (recalibrate) the arm offset&gain voltages until you are pretty sure you have lubricated and cleaned everything, and replaced the electrolytic capacitors on the arm deflection circuit(s)!!

[Dave in Green]

flavio81, don't worry, I always save the most difficult options for last, and only if needed! In this case, I've used synthetic grease and teflon oil on every moving part, which wasn't too hard. Replacing electrolytic capacitors would be hard for me, as I have no experience working with electronic components.

The good news is that it looks like I won't have to do that. Today when I tried playing more vinyl, the tonearm advance was again working intermittently. So I took the next step of removing the bottom board (which is very easy) and cleaning up the three wiring plugs connected to the sides of the main PCB.

That did it. I just finished listening to about a dozen of my old vinyls, and it tracked them all perfectly without a single skip or hesitation. The tonearm advance problem was apparently due to a dirty wiring plug.

Now that the major problem has been solved, I notice another problem. Every time the tonearm advances, I can hear a slight rumble from my speakers. It only happens when the tonearm advances while playing a vinyl. I tapped on the the side of the turntable, and a similar rumbling sound came from the speakers. So I think the cartridge (Ortofon TM14) may be picking up the slightest mechanical vibration in the turntable. I don't remember it being so sensitive when I was using it many years ago.

I have the SL-7 grounded to an ART USB PhonoPlus preamp, and the overall sound is great. So I can't figure out why the turntable transmits the slightest mechanical noise into the preamp, amp and speakers.

[fscl]

DiGreen writes:

Now that the major problem has been solved, I notice another problem. Every time the tonearm advances, I can hear a slight rumble from my speakers. It only happens when the tonearm advances while playing a vinyl. I tapped on the the side of the turntable, and a similar rumbling sound came from the speakers.

CONGRATS.....

It looks like the SL-7 has come back to life......

The advance should not cause any rumble or transmit any noise through the cartridge to the system.......

Somewhere there is some kind of mechanical acoustic coupling / touching / rubbing going on..... perhaps a screw slightly out of line, etc...

Somewhere, the tonearm not completely free and gimballed from tonearm drive system / dust cover.....

Edit: If you do tap the dustcover on all Technics linears you will experience feedback through the system as the tonearm is built into the lid. However, if you tap the base, you should hear nothing or just the what the base transmits to the dust cover and back through the dustcover.

EXCELLENT on getting tracking and tonearm movement sorted.

Fred and happy another SL-7 is turnin' tunes.....

[flavio81]

Now that the major problem has been solved, I notice another problem. Every time the tonearm advances, I can hear a slight rumble from my speakers.

Mine has that problem, it diminishes (or even dissapears!) if i re-lubricate the tonearm slide rail. BUT i am pretty sure the problem is caused by the tonearm drive string being not tight. So it needs replacement i think.

[fscl]

Now that the major problem has been solved, I notice another problem. Every time the tonearm advances, I can hear a slight rumble from my speakers.

Mine has that problem, it diminishes (or even dissapears!) if i re-lubricate the tonearm slide rail. BUT i am pretty sure the problem is caused by the tonearm drive string being not tight. So it needs replacement i think.

Quick thought, IIRC the tonearm drive motor is held in by metal strap with rubber cushion / gasket / spacer.

Perhaps the cushion no longer has any "cushioning / isolation" effect and may have to be "renewed" (rubber re-conditioner) or replaced, causing the motor vibration to be transmitted to the cover.

Good luck.

Fred and wondering if you backed off the screw / tightening torque securing the drive motor strap, things may improve.....

[Dave in Green]

I was suspicious that my problem was caused by the only mechanical change I made -- replacing the original tonearm drive belt with a rubber O-ring of approximately the same size. The O-ring I used was actually a little fatter and shorter than the original drive belt, and I remember thinking when I installed it that it might be putting more tension on the tonearm drive system.

So I took a second look at the original belt that was off the pulley when I first removed the cover. It looked and felt to be in pretty good shape, so I removed the cover again and replaced the new O-ring with the old drive belt. It seemed like a pretty loose fit. But I decided that was probably a good thing in terms of not transmitting vibration to the tonearm.

When I buttoned it back up, fired it up and put on a vinyl, the tonearm operation was now butter smooth. It's much, much better than with the O-ring. And it's completely silent. So that's one to add to the tribal knowledge about the SL-7: Do not substitute a tonearm drive belt that is not identical in specification to the original. This turntable is a fantastic piece of engineering, and the slightest wrong change can muck it up. I'm going to order an original equipment replacement belt to back up the original in case it keeps falling off or fails completely.

I'm pretty much in awe right now as I just finished listening to Steely Dan's Aja in vinyl for the first time in about 15 years since I changed over to CDs. Yes, I did hear a few small clicks and pops. But the overall sound stage is just staggering. Now I'm ready to invest in new vinyl cleaning equipment and a new stylus for the old Ortofon TM14, as the old stylus must have several hundred hours of use from the good old days. And now the good old days are back!

[flavio81]

Quick thought, IIRC the tonearm drive motor is held in by metal strap with rubber cushion / gasket / spacer.

Perhaps the cushion no longer has any "cushioning / isolation" effect and may have to be "renewed" (rubber re-conditioner) or replaced, causing the motor vibration to be transmitted to the cover.

The vibration is on the horizontal component, not vertical. So i doubt that rubber has anything to do. It is (i am 100% sure) due to the arm advancing in a jerky (jumpy, not smooth) manner; but then why causes this? as i said, i think is a combination of the tonearm guide rail having too much friction and the tonearm string being not tight.

...ALTHOUGH maybe they both can be perfect but the tonearm motor rubber BELT can be creating the jumpy advance due to slippage or lack of strength!!

[flavio81]

We should create a sticky thread for the linear trackers!!

[fscl]

f81 writes:

The vibration is on the horizontal component, not vertical. So i doubt that rubber has anything to do. It is (i am 100% sure) due to the arm advancing in a jerky (jumpy, not smooth) manner; but then why causes this?

I really don't understand this statement. When everything is working correctly, as DiGreen attests, the movement should be "buttery smooth.... And it's completely silent".

If your SL-7 arm is advancing in a "jerky (jumpy, not smooth) manner" then it is not working correctly. The tonearm, while playing an LP should not be perceptibly displacing sideways causing the tonearm drive motor to advance in "jerks, jumps" / like it's catching up....

I've never seen my tonearm motor in action, however, I imagine it is a slow continuous motion while the LP plays and this tonearm rotational motion is virtually silent with NO rumble or jerking necessary to keep the arm in coordination with the LP rotation. The action is like a pivoting arm, smooth movement of the arm across the LP surface.

This is true with all of my Technics linears.

@DiGreen..... CONGRATS

Fred and it's fun to watch my linears track an off center LP... the tonearm wags like a dog tail and makes for some really seasick sounds....

[Dave in Green]

The vibration is on the horizontal component, not vertical. So i doubt that rubber has anything to do. It is (i am 100% sure) due to the arm advancing in a jerky (jumpy, not smooth) manner; but then why causes this? as i said, i think is a combination of the tonearm guide rail having too much friction and the tonearm string being not tight.

...ALTHOUGH maybe they both can be perfect but the tonearm motor rubber BELT can be creating the jumpy advance due to slippage or lack of strength!!

I know for sure that the jerky advancing of my tonearm made a vibration that could be heard through the speakers. In my case, the cause was definitely a replacement for the drive belt that was too short and tight.

I think there are many things about the tonearm drive system that could cause a jerky motion -- too tight or too loose drive belt, not enough lubrication, problem with tonearm drive rope, maybe even a problem with the tonearm drive motor that would cause it not to run smoothly.

[flavio81]

f81 writes:

The vibration is on the horizontal component, not vertical. So i doubt that rubber has anything to do. It is (i am 100% sure) due to the arm advancing in a jerky (jumpy, not smooth) manner; but then why causes this?

I really don't understand this statement. When everything is working correctly, as DiGreen attests, the movement should be "buttery smooth.... And it's completely silent".

If your SL-7 arm is advancing in a "jerky (jumpy, not smooth) manner" then it is not working correctly. The tonearm, while playing an LP should not be perceptibly displacing sideways causing the tonearm drive motor to advance in "jerks, jumps" / like it's catching up....

Exactly, exactly. That's what i'm trying to say. The vibration only appears if the movement is not buttery smooth.

[fscl]

f81 writes:

The vibration only appears if the movement is not buttery smooth.

Is the movement of your SL 7 tonearm not buttery smooth and silent? Does it degrade over time?

After removing excess, old, decrepit grease, relubing with modern lubricants along with tonearm belt inspection / replacement, I've never had any other motion than buttery smooth silence while playing an LP.

Barring any major abuse / unuse, I expect my Technics linears to last / play maintenance free forever?...... These units are very well designed and some are built like tanks.... see "H" designations on linear spreadsheet.

This thread along with the parallel SL-QL1 cueing should be combined and turned into a Technics Linear sticky.

Fred and the only vibration I get is with my more (ab)used SL-QL1 sniped on fleabay originally considered for parts but revived and working and only experiencing a mild "thunking" when cued at fast speed inward... , but buttery smooth and silent while playing an LP and at other cue speeds, out-slow & fast, in-slow...... and considering opening her up again to see if I can correct this....