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Diagnosing / repairing infrequent turntable RPM variance, very brief & infrequent speed / pitch changes-Technics SL-B1
Jenni28
post Jan 23 2011, 23:58
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This Technics SL-B1 turntable - given by son - has very short (maybe 1 - 2 sec) & infrequent (1 or 2x / LP side??) changes in pitch - quite audible. It's one w/ a pitch / RPM adj wheel & strobe. Maybe this was a seriously cheap unit when new & basically P.O.C. No idea. Never had a pitch problem w/ the direct drive Dual that my son borrowed the cartridge from, but then, it wasn't decades old.

God knows how old this is (S.N. = 001 [kidding] - it's MS1116C161), & could be due to lubrication. Again, I'd expect it to occur more often.

The changes are over so quickly, can't look at the platter / strobe to see if shows anything changing. Have it hooked up to an UPS w/ AVR (automatic volt. regulator). Assuming that works, changes in speed shouldn't be due to voltage variations - but haven't checked voltage changes, much less monitored over 15 - 30 min period.

I believe it's belt driven (not had apart) & problem could be belt slipping, but I'd expect it to occur more often if it was. 99.9% of time, no audible pitch changes.

*** Have noticed the pitch adj (wheel) doesn't hold the speed constant. Could be # of reasons, incl. bad electronic components in rheostat. I used this type table in '70's, & most showed the markings fairly stable. Sure, there was slight variation back & forth, but not from markings dead still to moving at pretty good clip.

The strobe / markings on this Technics start to drift up / down from stationary, then maybe back to stationary for a few min. But I can't tell change in pitch when that happens. It's very touchy - a micro turn of the adj wheel may cause markings on platter to start spinning considerably. One's I used in '60's - '70's had much less sensitive adj wheels. ("You're livin' in the 60's, man!)

Haven't looked at the guts of adj wheel either - if it's mechanical variable rheostat or strictly electronic.
Any suggestions (toss it?)? Thanks.
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DVDdoug
post Jan 24 2011, 20:15
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That's a strange symptom.

QUOTE
It's very touchy - a micro turn of the adj wheel may cause markings on platter to start spinning considerably...

...Haven't looked at the guts of adj wheel either - if it's mechanical variable rheostat or strictly electronic.
This could be the source of the problem. It's probably a Potentiometer (rheostat). A noisy/dirty pot can usually be repaired with some Tuner/Control Cleaner. Sometimes, just working the pot back-and-forth several times can help, but it's best to use some control cleaner. (i.e. If you've ever had a noisy "scratchy" volume control, this could be the same kind of problem.)

Otherwise, the belt is probably the most common "failure" or "wear" item. And/or the lube in the bearings may have become gummy. I assume the "B" means "belt". I had a SL-D1 which was direct drive, and I still have an SL-D3 direct drive.
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Jenni28
post Jan 24 2011, 21:46
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Thanks. Yes, it's belt.
Anyone know where I could find the specs on the SL-B1, or for my Dual 1218? I've looked hi & low. Only thing can find is sites wanting to sell old manuals for very inflated $. Still have manual for the Dual - no specs.

The Dual's a dir drive, but I found it to be quite acceptable when recording new LPs to Reel to Reel in '70's. I monitored w/ a pair of upper end (at the time) Koss phones. I never noticed any introduced noise from the table & I was using a nice Marantz amp & very expensive speakers, which I played quite loudly, to my mother's chagrin. Aw, Mom! rolleyes.gif
(That could explain some of the ringing in my ears).

You may be right about the pitch control being the prob. I can pop off bottom & see how it works. Some brands/ models used a idler pulley that moved up / down a tapered drive shaft (least on dir. drive). If it's electronic & can clean w/ contact cleaner, will see.

As someone that's worked on cars & electronics for decades, it'd really surprise me if a slipping belt only caused audible problems once in a great while. If was belt slipping for say, 1 sec, don't think the platter could slow down, then get back to "normal" speed that quickly. Too much momentum. Sounds like some kind of "braking" issue, or something entirely diff - whether the pitch adj or other.

Why only slip 1x / side? Or none at all, for several records, then 1x on a side? Doesn't make sense, unless there's something diff about this belt driven device than hundreds of others I've encountered. Usually w/ audio equip, once belt stretches out & maybe heats up, it slips & audibly changes pitch quite often. Right now, it's very cool in our house - 69 - 70 F.

Belt on it is elastic - not dried / hard. Don't know what tension should be when stretch belt over to drive spindle, but it's fairly tight. Definitely "snaps back" against spindle when I let go.
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DonP
post Jan 24 2011, 23:05
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QUOTE (Jenni28 @ Jan 24 2011, 15:46) *
You may be right about the pitch control being the prob. I can pop off bottom & see how it works. Some brands/ models used a idler pulley that moved up / down a tapered drive shaft (least on dir. drive). If it's electronic & can clean w/ contact cleaner, will see.


If it uses an idler pulley, then it's not direct drive, right?


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DVDdoug
post Jan 24 2011, 23:35
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Another option is to transfer the cartridge to the Dual.

QUOTE
As someone that's worked on cars & electronics for decades, it'd really surprise me if a slipping belt only caused audible problems once in a great while.
I agree. wink.gif I just wanted to say that most speed problems I've seen in turntables & tape decks have been caused by rubber belts & drive wheels. OTOH, many old direct-drive turntables are still working fine...

QUOTE
I never noticed any introduced noise from the table...
Yeah, I never heard "rumble" or a wow & flutter from any (properly working) turntable. The REALLY BIG problem was the "snap", "crackle", and "pop" from the record (and generally poor sound from poorly produced/manufactured records), And, a bit of hum/hiss from the preamp, and sometimes a little hiss from the record surface or master tape.

This is a bit off topic, but This page has tons of information about digitizing LPs & cleaning-up the vinyl noise. I use the related Wave Repair for removing clicks & pops. It's time consuming (in the manual mode), but it does a great job and it only affects for the few milliseconds where the recording where you identify a defect.

This post has been edited by DVDdoug: Jan 24 2011, 23:38
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Jenni28
post Jan 25 2011, 01:50
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QUOTE
If it uses an idler pulley, then it's not direct drive, right?

Yes, that's not right, or, No, that's correct. My Dual is direct drive & uses an idler wheel (not pulley - I misspoke) that moves up / down tapered motor shaft to slightly change speed of idler wheel, which engages a flange on the platter. The motor shaft has 3 steps for 3 speeds & each one is tapered slightly.

Current problems aside, the Technics SL-B1 specs I found (who knows if they're correct) are a bit better in wow/ flutter & rumble than my Dual specs, even though the MSRP was much higher on the Dual. Some mfgs fudge their specs more than others, or may be I never had sensitive enough ears to detect differences. If I can't fix the Technics, I'll drag out the Dual.

Yes DVDdoug, I've seen that page several times - others will find it useful. I have several wave repair / noise editing prgms to occupy my time. They all have their pros / cons (what little I've used them). Nero 9 Wave Editor (& SoundTrax to record), Audacity (1.3.12b), Creative X-Fi Titanium's software pkg & Cool Edit 2.0 (last ver before Sony bought it & changed name).

Nero's a little light on explanation of what some settings do, but their auto declicker / decrackle / denoise (all separate w/ several settings on ea) work pretty good if fool w/ levels a bit. Not the most intuitive prgm I've ever used, but once learn it, works as advertised.

Audacity is a nice prgm. Like Nero, has way more than I'll ever use. Pretty good documentation - better than Nero's IMO. I like Audacity's equalizer a bit better & has record / play peak meters, even when have waveform windows fill entire screen. Many of its components are written by different people. I imagine it works well once learn it.

Creative's wave repair isn't bad, though I've not tested it on LPs. It's a little light in the loafers - but it is free. Haven't tried Cool Edit but lots of folks have used it for many yrs.
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Glenn Gundlach
post Jan 25 2011, 04:39
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You mis-understand the concept of 'direct drive'. Your 1218 uses an 1800 RPM (4 pole) synchronous motor with a conical pulley. The pitch control varies the height of the idler to change the 'gear ratio' and therefore the speed. Still, if the line frequency changed (it never does) the speed would change porportionally. My Dual 721 is a true direct drive table. The motor runs at 33 1/3 or 45 RPM without belts or idlers. The advantage is no vibration induced rumble. Direct drive speed is maintained with a servo system totally independent of line voltage or frequency. Some are crystal referenced but as Dr Richard Greiner, UW Madison electrical engineering professor in the '70s said, "it's an elegant solution to a non-existent problem".

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DonP
post Jan 25 2011, 13:41
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QUOTE (Glenn Gundlach @ Jan 24 2011, 22:39) *
You mis-understand the concept of 'direct drive'. Your 1218 uses an 1800 RPM (4 pole) synchronous motor with a conical pulley.


I should have noticed the model number, as I have a 1214 on the shelf (using a direct drive 622 now).

Idler wheels have the same issues as belts in having to stay soft enough to get good grip, plus performance is dependent on staying perfectly round.
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Jenni28
post Jan 25 2011, 17:25
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Glenn - I didn't misunderstand the direct drive concept. But you're correct, the idler wheel design is a variation of belt driven, so technically it's not a direct drive. But it's not belt driven, either. That's what I should've said, "Idler wheel driven instead of belt driven." Thanks for pointing it out.

All good info, but we're getting slightly off topic (myself, as well).
1st, I'm not an electronic repairman! Maybe now that cause of pitch problem seems to be identified, others have further suggestions on dealing w/ the problem (read on).
The pitch speed adj on Technics SL-B1 is purely electronic. The voltage from the AC to DC transformer was consistent.

Checked the only resistor (other than variable ones) - was at specs. Have no way to check a capacitor on this pc.

For each speed (only 45 & 33), there's a variable resistor ( I believe). They are ~ 1/4 in. in dia across top (round, grayish blk).
There's 2 parts to them - a lower stationary & upper section, same dia. as lower, & upper part can be rotated w/ sm. screw driver. Each is labeled on the board "45" & "33". These then feed the motor. These may be what are called speed pots?

Guessing after 30 yrs, the continuity between upper / lower half might not be good, I rotated them back & forth from each stop several times, noting original position of each rotating top half. Didn't use any contact cleaner - to start.

Plugged 'er back in & pitch adj wheel now seems to adj pitch up / down consistent w/ how much the wheel is turned. During short test, stroboscope / pitch adj now seems to hold platter at constant speed once adj, w/ only slight movement of platter marks - back & forth, varying by one mark, (occasionally). From memory - 30+ yrs ago - most all tables w/ strobes showed very slight movement of the platter marks. Long time ago!

Tiny movement of pitch adj wheel no longer causes wild speed changes. Turning pitch wheel causes smooth incr / decr of platter speed. No telling if fix is permanent, but obviously those were the components related to pitch problem. Won't call this "solved," until use it for long periods.

Jury's still out, but * appears * my theory may be correct - belt slip wouldn't cause such very short & infreq. pitch changes. Now on to issue of different cartridge - another post.

Glen wrote:
QUOTE
The advantage is no vibration induced rumble.

I'd always thought (& thought I read) that belt driven tables were supposed to have LESS rumble or other noise from motor itself, because table was isolated from motor? Is that not correct (comparing tables from similar price / quality)?

This post has been edited by Jenni28: Jan 25 2011, 17:32
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cliveb
post Jan 30 2011, 11:18
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Apologies for coming in late - I've been away on a skiing trip last week. I have a couple of comments.

QUOTE (Jenni28 @ Jan 25 2011, 16:25) *
Glenn - I didn't misunderstand the direct drive concept. But you're correct, the idler wheel design is a variation of belt driven, so technically it's not a direct drive. But it's not belt driven, either. That's what I should've said, "Idler wheel driven instead of belt driven." Thanks for pointing it out.

As a general rule, idler wheel drive is the worst of the three standard methods - belt drive and direct drive are typically much better. But if anyone can execute idler wheel drive well, Dual would be on the shortlist. Not that I know anything about the 1218, though.

QUOTE (Jenni28 @ Jan 25 2011, 16:25) *
Jury's still out, but * appears * my theory may be correct - belt slip wouldn't cause such very short & infreq. pitch changes. Now on to issue of different cartridge - another post.

Have you seen this thread on the SH forum: http://www.stevehoffman.tv/forums/archive/...p/t-139348.html? (I know that here on HA we think that the SH forum is stuffed full of loonies, but it's worth a look). This comment caught my attention because it sounds very much like your problem with the SL-B1:
If long term testing reveals gross speed fluctuations (where it is playing fine, and suddenly slows down noticeably), then the circuit board capacitors may need replacing.
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Jenni28
post Jan 30 2011, 19:04
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Thanks Clive, for the link. I wasn't familiar w/ SH forum. One poster in the link you gave to SH, Rolf Erikson (who MAY be same as Rolf Ohlsen???) may be same person that runs Vintage TX audio repair & supplies place. In post, indicated he sells supplies. If is same person, was very helpful via email at Vintage TX, though I've not bought anything - so can't endorse, yet.

Good info to know if what I found as possible solution to speed varying (via email to a repair place) is try cleaning the "speed pots" as he called them. I described them above. I didn't even clean them - yet - just turned back / forth w/ tiny screw driver. I would post pic, but can't upload files on this forum?? Immediately after, the speed variation problem / strobeoscope markings fluctuating went away. *(NOTE: mfg / expert info confirmed the RPM markings on TT will vary - 'rock' - a tiny bit, due to natural variance in elec line freq. - "normally" 60 Hz in U.S.).* Time will tell if that is only problem, but others should look at that 1st for same problem symptoms. You could use contact cleaner. Poster in SH forum suggested naptha, though no idea why. I can see using it to clean grease, etc. off, but not as final step.

Re: Dual drive type. We all kind of got off topic, as we all tend to do. That Dual 1218 had slightly poorer wow/flutter & rumble specs than my freebie Technics SL-B1 - when both were NEW. The Dual is 38 yrs. smile.gif But, not sure diff is enough to worry about. Dunno. Right now, torn between getting my Sony R-R working or buying a very decent stylus for my Pickering XV-15. Will fit both TT's. ** IF ** the R-R tapes are still good sound quality, AND Sony will play them properly w/o investing way too much$, the recordings on my tapes were 90% off pristine LPs. Whereas, the LPs I have to digitize are not generally pristine, requiring much more time using wave editing. My health sort of limits time I can spend working on old equip or # of hrs spent at computer cleaning up WAV files.

R-R tapes (BASF best quality) have always been stored in AC / heated area. But have NO idea if quality after 38 yrs will be worth digitizing, until spend $ on the RR deck & don't know anyone w/ a working R-R deck to test tapes. If looking at it only from economic view, quickly reach a point where $ & time repairing 40 yr old audio equip far exceeds buying old rock albums released on CDs. Restoring old equip as hobby is fine & I really like that stuff, but not necessarily the cheapest or fastest way to get old LPs digitized. I'm fast approaching the breakover point.
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eevan
post Jan 30 2011, 21:04
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QUOTE (Jenni28 @ Jan 30 2011, 19:04) *
You could use contact cleaner. Poster in SH forum suggested naptha, though no idea why. I can see using it to clean grease, etc. off, but not as final step.

That's what DVDdoug suggested in the first reply. Use a dedicated contact cleaner, cause they also contain lubricant. I used Tuner 600 by CRC Kontakt Chemie and Philips 390 CCS.


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Jenni28
post Jan 31 2011, 15:29
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QUOTE (eevan @ Jan 30 2011, 14:04) *
Use a dedicated contact cleaner, cause they also contain lubricant. I used Tuner 600 by CRC Kontakt Chemie and Philips 390 CCS.

I don't know that all contact cleaners contain lubricant - but not 100% sure either way.
Thanks for info about CRC's Tuner 600 - haven't seen that one. Which / what type store(s) sells it in your area? Only electronics, or hardware / home centers, too?

If others go to store looking, they sell lots of CRC products in my area, but they often only show "CRC" in sm. print somewhere on product for some products, like lubricants.

eevan - A close relative is named "Evan" - I always suspected the name was of Russian (in your case, Serbian) descent - yes? Perhaps a variation of Ivan?

This post has been edited by Jenni28: Jan 31 2011, 15:33
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eevan
post Feb 1 2011, 22:42
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QUOTE (Jenni28 @ Jan 31 2011, 15:29) *
Which / what type store(s) sells it in your area? Only electronics, or hardware / home centers, too?
Electronics stores sells Kontakt Chemie products here.

QUOTE
eevan - A close relative is named "Evan" - I always suspected the name was of Russian (in your case, Serbian) descent - yes? Perhaps a variation of Ivan?
Well, I don't know the origins of name Evan, but you're right, my name is actually Ivan. Here we don't use name Evan. Instead of writing „I” uppercase, I prolonged it (like in „green”), hence username is eevan smile.gif


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Jenni28
post Feb 2 2011, 02:49
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Yes, eevan / Ivan, some persons from Europe sometimes pronounce his name ee-von (long 'e', as in green). I'm pretty sure they're variations of the same name, but not sure of the derivation or Evan.
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Arnold B. Kruege...
post Feb 2 2011, 13:42
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QUOTE (Jenni28 @ Jan 23 2011, 17:58) *
This Technics SL-B1 turntable - given by son - has very short (maybe 1 - 2 sec) & infrequent (1 or 2x / LP side??) changes in pitch - quite audible. It's one w/ a pitch / RPM adj wheel & strobe. Maybe this was a seriously cheap unit when new & basically P.O.C. No idea. Never had a pitch problem w/ the direct drive Dual that my son borrowed the cartridge from, but then, it wasn't decades old.


This exact problem can be caused by a grease spot on the drive belt.
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Jenni28
post Feb 2 2011, 18:03
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Arnold, yeah, sounds like a grease spot on belt might do it. Wonder if played very long, the grease might transfer to capstan, then onto other areas of belt? Then would have intermittent pitch fluctuations. Depends on type grease & amt, I guess. Don't believe was the cause in my case.
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Arnold B. Kruege...
post Feb 3 2011, 14:19
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QUOTE (Jenni28 @ Feb 2 2011, 12:03) *
Arnold, yeah, sounds like a grease spot on belt might do it. Wonder if played very long, the grease might transfer to capstan, then onto other areas of belt? Then would have intermittent pitch fluctuations. Depends on type grease & amt, I guess. Don't believe was the cause in my case.


I've never worried long about a dirty belt being a problem because belts are easy enough to clear. Just find some electronic cleaner that says it is good for rubber parts and a paper towel or two. Sometimes there is stuff you can't see that causes problems.
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stephan_g
post May 29 2011, 01:29
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Old thread, I know.
QUOTE (Glenn Gundlach @ Jan 25 2011, 04:39) *
Direct drive speed is maintained with a servo system totally independent of line voltage or frequency. Some are crystal referenced but as Dr Richard Greiner, UW Madison electrical engineering professor in the '70s said, "it's an elegant solution to a non-existent problem".

As the proud owner of a SL-BD20 which in direct comparison is playing audibly fast and didn't feel like exposing its adjustment pots when I was poking around in the nominally right spots (at least as per the SL-BD21 service manual *), I'd have to disagree here. If I'm going through the trouble of recording, editing and converting, I don't want to find out that the pitch is off afterwards. That kinda put a damper on my vinyl digitizing activities. Stupid thing has some rumble, too. (Maybe I'll give the platter bearing some oil, but I don't think that's it. Almost impossible to reach, too.)

Now of course it doesn't matter whether rotational speed is referenced to mains frequency or a crystal oscillator, as both will be sufficiently accurate. Rotational speed should, however, be firmly locked to that reference without a chance of oxide layers in adjustment pots messing things up. (Guess my next turntable will have a strobo and pitch control, possibly with pitch defeat.)

*) EDIT: With the help of a flashlight, it turns out there only is empty PCB behind the adjustment holes. Ah well, that's budget turntables.

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Glenn Gundlach
post May 29 2011, 05:46
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QUOTE (Arnold B. Krueger @ Feb 2 2011, 04:42) *
QUOTE (Jenni28 @ Jan 23 2011, 17:58) *
This Technics SL-B1 turntable - given by son - has very short (maybe 1 - 2 sec) & infrequent (1 or 2x / LP side??) changes in pitch - quite audible. It's one w/ a pitch / RPM adj wheel & strobe. Maybe this was a seriously cheap unit when new & basically P.O.C. No idea. Never had a pitch problem w/ the direct drive Dual that my son borrowed the cartridge from, but then, it wasn't decades old.


This exact problem can be caused by a grease spot on the drive belt.


He says it's infrequent, maybe 1-2 times in 15 minutes. The grease spot would spread out eventually. He also says the pitch control isn't stable. It may be as simple as a dirty speed pot. If that is indeed the problem I wouldn't bother trying to clean it, just replace it. A pertinent question is if the Technics is a P.O.C, where is the Dual?

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