Sl-7 Disassembly Problem

turning japanese
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invisibleorange
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Re: Sl-7 Disassembly Problem

Post by invisibleorange » 05 Aug 2014 03:35

Just wanted to post a quick THANKS here. This thread helped me chase down a couple of issues with my Technics SL-6. Now it's right as rain. Kicking back with Tull's "War Child".

Skating away... on the thin ice of a new day.....

Cheers!

-IO

andrewb
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Re: Sl-7 Disassembly Problem

Post by andrewb » 20 Aug 2014 06:28

I will probably be back to this thread myself soon. I'm probably picking up a "mint" (we will see about that) SL-7 with the runaway speed issue later this week. I've had an SL-5 for awhile, on which I have only had to replace the belt, but I think it's time to trade up! :)

fscl
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Re: Sl-7 Disassembly Problem

Post by fscl » 27 Aug 2014 16:24

Not an SL-7, however, a Technics linear servicing U toob for reference:



Happy restoration of Technics linears...... :)

Fred

healthyhouse
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Re: Sl-7 Disassembly Problem

Post by healthyhouse » 04 Sep 2014 18:23

If this is still open and being read, what is the real difference between some of the top models? sl-7, sl-10, sl-ql1, etc. I know about the built-in step up amp in the 10, and some of the programmable electronics, but not much else that I can find. Thanx for any help on this.
BTW, I just landed an SL-7 with Ortofon TM14 delivered to my front door for $77, all it needed so far was a cleaning of the old peanut butter-like grease from the arm gears. I cleaned the stylus and cart with a magic eraser and some turntable liquid cleaner. Put it under a scope - wow! what a diff. The pics tell the story. Went from a cruddy lump of rock to a shiny cut diamond.
Istill have some arm issues, it seems a bit out of line on some inner tracking. Sometimes it gets off kilter.
And a couple small electronic intermittent issues - like a loose wire issue or something - and the sound goes out for a second. Just haven't gotten to those since 99 percent of the time it sounds great.
Finally, I need advice on lubes and grease -- some people say white lithium, others say other stuff. I don't know which to do.

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 05 Sep 2014 13:30

we told you all about this in the other thread HH :)

andrewb
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Re: Sl-7 Disassembly Problem

Post by andrewb » 05 Sep 2014 18:09

Lensman, did you re-cap the entire board or just around the speed control area? I replaced C201 and 208, and even tried 208 reversed based on your post, but with luck so far. How about Q202? I hear it might be a suspect too.

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 05 Sep 2014 23:28

yes i recapped everything andrew,im no electronics engineer but yes id go for q202 first with it being the FGamp,but id advise replacing all of the caps in the speed control section first,i think theres around 6 in total.

shame they dont give a proper diagram with voltages for the different transistors,would make fault finding a bit easier!

healthyhouse
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Re: Sl-7 Disassembly Problem

Post by healthyhouse » 03 Oct 2014 19:49

I was on the SLQL1 forum and was directed here for an SL-7 problem.
There is a Low frequency very short thump when the arm motor engages to advance the tonearm toward the center during play - so I hear the repeated thump thump thump thru out the entire playing. It was not noticeable once I freed up the gears and cleaned some of the old sticky yellow grease. It started after I completely removed cleaned the old grease and applied new lithium grease to the worm gear/rope gear and synthetic sewing machine lube oil on the tonearm guide rail.
At that point I thought it was due to an old loose misshapen belt so replaced that.
But, It continues.
It is very low frequency, sounds like I am lightly tapping on the lid, it is very loud and noticeable when I use my subwoofer, and less so when I don't. Note: I use the unaltered direct stereo pass-thru (no sub) on the amp system (Denon AVR-2312).
Thanx for any ideas.

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 03 Oct 2014 21:00

try putting some oil in the top of the motor spindle for the arm drive motor.

failing that a thump might be the servo is off;so the tonearm is getting so far over,tripping the sensor voltage which then causes the motor to kick in double quick to make up the error.

healthyhouse
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Re: Sl-7 Disassembly Problem

Post by healthyhouse » 04 Oct 2014 02:51

Lensman, the servo does go off and on, it only goes on (to move the belt, arm, etc) when the arm moves over enough to trigger it, like 2,3,4 rotations worth. isn't that how the motor's supposed to work -- on/off/on/off (stop/turn/stop/turn). I can not find where the sensor for the arm is (not by looking or in the service man), and does the motor gain adjustment change this level of response? or will it simply slow it down enough to not play catch up as you suggest?

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 04 Oct 2014 13:04

yes thats how it should work,but its the amount of arc the arm has to travel to trigger the servo to move the arm;so for arguments sake the arm will move say 5 degrees before moving as opposed to 20 degrees and that might cause a thump as the arm motor has to rotate faster to catch up.im only summising its the motor,could be something completely different.

also no need to worry about the sensor,the adjustment screws are on the back behind the ADJUSTED sticker,i did mine a few months back,fred was good enough to link to the writeup i did earlier in this thread.

healthyhouse
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Re: Sl-7 Disassembly Problem

Post by healthyhouse » 04 Oct 2014 22:18

found the sticker - pretty obvious! thanx. will consider that.
however, i don't think the motor has speed, I'm pretty sure it turns at a steady speed, it's a servo mechanism, so it is directed to rotate the correct distance, not fast or slow. so my guess, if the thump is from the motor it's like a torque thump. not sure, just a guess. I can't find any places the arm mechanism might 'bump' to cause the thump. i can test it with the arm cover off and the lid in the up position, and haven't seen, felt, heard anything other than the motor. not sure how if it's a ground loop issue, or a loud old switch issue (like when you first start an auto table and the old mute switch kicks off and you get the thump/crack noise thru your speakers.

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 04 Oct 2014 23:25

true,the motor can run at 2 different speeds though,is there any play in the spindle? another thing you could try is isolating the motor a bit more,maybe a bit of extra rubber under the mount? at least then you'll be able to rule it out.

another idea;hows the drive rope?

healthyhouse
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Re: Sl-7 Disassembly Problem

Post by healthyhouse » 05 Oct 2014 03:35

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.
today, when this happened, the pulley and rod would not pop back together, and it freely spins on the end of the rod. i noticed a tiny piece of material on the end of the pulley. when I took it off, there was about 3 small broken pieces, crescent shaped. amber color. at first, i thought it was brass. but no, some sort of plastic or glue.
when I got the pulley out, i see that is has a bevel edge around the rod hole. apparently, technics used some sort of glue/adhesive to hold the brass pulley on the rod.
here's the interesting part. when i put this back together, i find that if you leave off one washer the rod sticks out of the end of the pulley; when you put the washer back, the rod is exactly flush with the face of the pulley - exactly. so, the bevel leaves just enough space around the rod end to put a bit of adhesive.
Any ideas if this is correct?

lensmanMK2
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Re: Sl-7 Disassembly Problem

Post by lensmanMK2 » 05 Oct 2014 11:15

havent got a clue to be honest,never run into that! sounds somthing similar to anti tamper glue you put on screws.

take a pic and maybe fred and others can chime in?

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