Technics SL-B2 warble - is it fixable?

[ASeattle]

Hi all,

I just discovered this great forum for TT discussion and am wondering if you can help me. I have an old Technics SL-B2 and it has a distinct tendency to speed up or slow down. The speed adjustment helps correct the problem, but it still warbles and wavers.

The problem stems from a time when my finger got in the way when the arm was returning to the rest position, and seems to have messed up something.

I had it serviced a few years ago with a new belt, cartridge, etc. But it still warbled. I'm wondering if it could be fixed by spraying some Deoxit into some part of the pitch control. Or other ideas.

Thanks for any advice!

 

[Montycat]

Almost certainly a cleaning of the speed pot will help. Some oil in the motor might be a good idea too and it could be time for a new belt again.

 

[ASeattle]

Thanks for your help. To access the pots, do I open up the TT from the underside? And by cleaning, do I spray in contact cleaner? I have a cleaner called "Super Contact Cleaner" by MG Chemicals, which is for cleaning and removing oxidation from switches, relays, potentiometers, ICs, jacks, plugs, etc.

The motor makes a faint roaring noise when it spins without the belt. Where would one put in oil, and what kind? It surely can't be as simple as WD40!

 

[ASeattle]

I read in the Technics service manual that strobe speeds can fluctuate due to voltage shift from the power supply - with no change in record speed, since it is a direct current motor. By the way, I used a protractor from VinylEngine.com to adjust the cartridge in the headshell. It called for me to move the cartridge (an AT91B) all the way forward in the headshell. Sound is much, much better. Very full with crisp highs and punchy bass.

Still wondering about how to clean the pots and switches and oil the motor, if anyone knows!

 

[Dr Tinear]

If Vinyl Engine has the service manual for the SL-B2, download it and read it. Cleaning the pots is easy once you know where to find them. You will probably have to remove the bottom cover from the turntable (unplug it from AC power first, of course). You should find four pots in the circuit. Two of them are the user-accessible speed adjustments; the other two are coarse speed adjustment pots on the motor control board. Spray all four with DeOxit and exercise them, and treat the 33/45 switch as well.

If cleaning the pots and the 33/45 switch doesn't stabilize the speed, you may need a new belt or the electrolytic capacitors in the motor control circuit or power supply may be getting tired with age. For belts I recommend a genuine PRB belt instead of the cheap Chinese or Taiwanese knockoffs. On my belt-drive Technics SL-230, using a cheap belt resulted in audible flutter -- not severe, but enough that I could notice it. Replacing the belt with a PRB belt eliminated the problem.

 

[ASeattle]

Thanks Doctor! It seems to have worked. The patient is, amazingly, holding constant speed. The belt is very supple and fits well. Next question is whether to upgrade to a cartridge with more output than the AT91B. I'm looking at the Ortofon 2M Red or the Grado Prestige Black of Green. They both have higher voltage output than the AT - 5.5mV and 5mV, respectively. I'm basically cranking my 25 watt/channel NAD 302 amp to get a good sound out of my Paradigm Atom Monitor V.5s. Any thoughts?

 

[Dr Tinear]

Neither one of those cartridges will give you a huge increase in output level. The AT91B puts out 3.5 mV at a groove velocity of 5 cm/s (the standard test condition). The Ortofon will play about 3.9 dB louder than the AT; the Grado, about 3.1 dB louder. Acoustics experts say that a 3 dB change is a "just noticeable difference," so you won't hear much of a change. Unless you have to run the amp's volume control close to maximum to get the volume level you want, any of the three cartridges should be a good match.

That said, you'll probably get better sound quality from either the Ortofon or one of the Grados. The elliptical styli on those cartridges will draw more detail out of the record grooves with less distortion than you're getting from the conical stylus on the A-T. I'm not an Audio-Technica expert, but I know that they offer elliptical styli as upgrades for many cartridges in their line, so that could be another option.

 

[ASeattle]

Following up on this post....I got the Ortofon 2M Red cartridge, and it made a huge difference. The sound is two or three times louder now, and the clarity and detail are superb. With the old cartridge, I had to turn my amp up three quarters of the way, or more, to fill the room, and the sound was muddy. With the 2M Red, I only need to turn it up a quarter of the way and the sound is clear and musical. I played an old Verve record of Ella Fitzgerald singing Cole Porter songs, and it was tremendously open and sweet sounding. Bob Marley comes through with crisp drums and tight-sounding bass. Not sure if the Grado would have been even better, but this upgrade has restored life to my vinyl collection. My speakers, by the way, are Paradigm Atom V.5s.

 

[MacNoob]

If you're seeing a huge increase in volume swapping the cartridge, either the old cart or stylus was faulty (demagnetized?) or the action of swapping it corrected a poor connection or poor adjustment.

Either way, you've solved the problem and are enjoying your records the way they were meant to be heard.

I've had volume issues corrected by as simple an action as removing and reinstalling the stylus.

 

[ASeattle]

Thanks MacNoob. I wondered about that. The stylus of my old AT cartridge didn't sit firmly in place. In other words, it would wiggle in the slot in the cartridge. So that was certainly the problem.

Now, here's the next question....

I put the new Ortofon cartridge on the stock headshell from my Technics SL-B2. It sounded great, but I had also opted to buy a new Ortofon shell head, figuring new wires and a more precise metal headshell would be an improvement.

When the new headshell arrived a week after the cartridge, I noticed that it rotated slightly when I screwed it on to the tonearm. Did that take the cartridge out of alignment? I eyeballed it to see if it was level, but who knows. I tried the old headshell and it rotates a little, too, though not as much. Any thoughts on this? I assumed the Ortofon headshell would be better, but maybe vintage is best?

 

[Starquest]

Technics headshells are pretty much impossible to beat, especially for their turntables. Which vintage headshell do you have? Is it the metal or plastic one? I've had issues with newer, cheap, non-Technics headshells, and the azimuth problem you're talking about is frequently an issue. Now I just buy the OEMs on Amazon for $20.

But if you can get your Ortofon adjusted level, then it should be fine.

 

[grottyash]

Ortofon headshells are also impossible to beat

When you say rotated slightly, do you mean the needle is no longer vertical to the record? If so, that means the azimuth is not correct, which will affect the sound. You need to check the manual to see if it can be adjusted.

 

[MacNoob]

Loosen the headshell, rotate it to the angle you want (as close as you can get) and tighten it down while holding it in place. Typically there will be a little bit of play in the position of the headshell.

 

[hi*ball]

One easy way to get the angle correct is to put a mirror under the cartridge. You will be able to see the cartridge and its reflection and this will aid you in getting it aligned correctly.

Like this:

 

[ASeattle]

Thanks for the tips and alignment advice. The vintage headshell is black plastic with metal on the underside. It came with my Technics SL-B2 when I bought it back in 1978 or so. That tonearm looks nice, hiball. I'm going to try the Technics headshell again and see if I can hear a difference when I get time.

 

[eb2jim]

I'd be curious to see what you think. I tend to not hear much if any from a Technics to say adc headshells. For spares now I buy the Technics knockoff from Musicians Friend. They're $8 and virtually identical to Technics.

 

[hi*ball]

That tonearm looks nice, hiball. I'm going to try the Technics headshell again and see if I can hear a difference when I get time.

That is a nice tonearm. Unfortunately, it's just a pic I grabbed off of the internet. None of my turntables are that nice!

+1 for the $8 American DJ headshell.

 

[ASeattle]

It's funny, in addition to the azimuth concern, the Ortofon looks like it curves rather than being a straight extension of the tonearm. It could be my eyes playing tricks. I'll take a picture tomorrow and see what you guys think. $8 for a knockoff headshell. Really? The Ortofon was $20 something.

Having said that, my records sound pretty good.

 

[eb2jim]

Yep - $8 all day everyday. Like the early Technics head shells they don't have Technics printed on them. - plain black. Other than than there isn't a damn bit of difference between them. Except the price.