Technics SL-B2

turning japanese
HvdB
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Technics SL-B2

Post by HvdB » 12 Mar 2018 23:11

Hi, I recently purchased a Technics SL-B2 belt drive turntable from which the automatic mechanism suddenly stopped working. The arm doesn't return automatically at the end of the record anymore and also the stop button stopped working. I've been trying to find a solution and took a look at the service manual. Strange enough the pictures at the manual look different from my tt. I cleaned some grease and nothing seems to be broken. Anyone any idea?

Alec124c41
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Re: Technics SL-B2

Post by Alec124c41 » 12 Mar 2018 23:16

Some of those things that slide to change functions will stick very easily, because the grease under them is old and gummy. So cleaning some grease is not sufficient.

Cheers,
Alec

royal_mile
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Re: Technics SL-B2

Post by royal_mile » 13 Mar 2018 10:22

Hi

I agree with Alec, that old grease can cause serious problems for auto mechanisms.

There may be another fairly common issue:

From memory the SL-B2 has a small plastic gear wheel that fits over the spindle, they can shrink and crack with age. The gear wheel drives the auto return cam.

To check the gear wheel:
Remove the mat
Slip the belt off the motor spindle
Remove the platter
The gear wheel should be visible

If it is broken, a 3D printed copy can be purchased. Repair with wire and epoxy is also possible.

Steve

HvdB
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Re: Technics SL-B2

Post by HvdB » 13 Mar 2018 19:01

Thanks Steve, I found the gear wheel and it indeed was cracked. I will try to fix it with glue. Hopefully that will do the job. Do you have any idea how to get a printed one?

royal_mile
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Re: Technics SL-B2

Post by royal_mile » 14 Mar 2018 17:12

Hi

Just using glue may not be successful as the part sometimes shrinks and will crack again when you push it over the spindle.
I've used the following method which sometimes works ok:

Remove the gear wheel from the turntable.
1. Sand a small amount of material from the inside surface - I use a Dremel sandpaper refil by hand to do this.
2. Hold it together over the spindle and check for a snug fit especially where the crack is. If there's a gap, try sanding a little more material until you get a snug fit
3. Glue the crack and hold it together until the glue has set.
4. Clean off any surplus glue then re-fit the gear wheel


They are available from an ebay seller:

https://www.ebay.co.uk/itm/Technics-Tur ... SwBRVafH5Y

This one is based in the UK but it may be worth asking about shipping elsewhere.

HvdB
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Re: Technics SL-B2

Post by HvdB » 14 Mar 2018 19:17

Here is a picture of the mechanical unit, which I have disabled. I think the metal arm should be connected to something, but I don’t know to what part. It looks different from the drawing in the service manual.

HvdB
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Re: Technics SL-B2

Post by HvdB » 14 Mar 2018 19:20

IMG_2486.JPG
(104.86 KiB) Downloaded 475 times

royal_mile
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Re: Technics SL-B2

Post by royal_mile » 14 Mar 2018 20:21

If you try to turn the spindle with the cracked wheel, does the small wheel turn?

I sold my B2 a while ago but from memory ....

When the turntable is playing normally, the small gear wheel on the spindle should sit within the gap in the teeth on the large cam-wheel. In this scenario, the small wheel will always rotate with the platter, but the big cam wheel will remain stationary until the return mechanism starts.

The mechanism probably works as follows:
1. The lever arm moves the small metal lever on the large cam wheel towards the spindle.
2. An extension on the small gear wheel then catches the metal lever on the cam-wheel and rotates it enough to engage the teeth of both wheels.
3. One complete rotation of the cam wheel will cause the arm to return.

To test the mechanism while disconnected:
-make sure the mechanism is level or gravity may move the lever
1. First, reset the mech by moving the metal lever on the large cam wheel towards the centre of the cam wheel (it may already be in this position)
2. Turn the small gear wheel clockwise until it sits within the gap on the large cam wheel.
3. Check the small gear wheel spins independently of the cam wheel
4. Activate the lever - it should come across the cam wheel and nudge the cam-wheel lever.
5. Rotate the small gear wheel - it should catch the cam wheel and perform one revolution.

The underside of the cam wheel has a guide that moves a pin which, in turn, lifts the arm and swings it back.

Steve

HvdB
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Re: Technics SL-B2

Post by HvdB » 15 Mar 2018 17:21

Hi Steve, it works exactly as you described. I managed to fix the small gear and now everything works well again. First only the stop button worked, but finally also the automatic return at the end of the record. Thank you very much for helping me out!

Cheers, Hans

sanman68
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Re: Technics SL-B2

Post by sanman68 » 09 Oct 2018 16:52

Gentlemen you have managed to solve my technic sl be turntable issue. Cracked gear! I was just wondering how the last poster managed to fix it, replace or glue?

musicmn
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Re: Technics SL-B2

Post by musicmn » 09 Oct 2018 19:48

Hi, I just finished servicing a Technics sl b2 with a cracked gear. I used two ton epoxy to fix the crack. One thing that should be done before you try and glue this gear it make sure you clean it well with alcohol. That way the glue/epoxy will adhere better to the plastic. Then as stated just slowly file out the inside of the gear until it fits over the splined part of the spindle snuggly. I used the same epoxy to hold the gear on to spindle but again clean the spindle with alcohol first. This is the third or fourth gear I have repaired this way with no ill effects.

eddie edirol
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Re: Technics SL-B2

Post by eddie edirol » 09 Oct 2018 19:52

sanman68 wrote:Gentlemen you have managed to solve my technic sl be turntable issue. Cracked gear! I was just wondering how the last poster managed to fix it, replace or glue?
Replace first if you cant find a 3d printed part, glue as a last resort.

absurdbird
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Re: Technics SL-B2

Post by absurdbird » 12 Dec 2018 11:28

Hi guys.
First post here.
I came across this thread (and this forum) searching for exactly this problem with a Technics SL-B2 I found in the street.
Auto return was intermittent and jerky (crack mismatching with the gears). Stop button didn’t work at all.
Also; belt perished, no stylus.

Really glad it was a relatively simple (and free fix).
I’m so grateful that I’ve registered to thank you for your excellent nerdery, technical investigations and generous sharing of knowledge. =D>

My input;

• I didn’t know this kind or plastic shrinks.
• I cleaned out the cracks (my sprocket was still in one piece -just-) with 120 grit sandpaper -because I was impatient and didn’t have any isopropyl or methylated spirit- but also I think a mechanical key is good when glueing unknown plastics (nylon?)
• I rolled the sandpaper and reamed out the inside of the sprocket so it was a very loose fit.
• The enlarged cracks allowed me to get the glue (Araldite 5 minutes I had in a drawer) into them, I built up a layer around the inside of the sprocket to make a collar/cylinder of epoxy which will hold the whole lot together (I hope)
• I reamed out the set epoxy with the sandpaper roll carefully, until the sprocket fitted tightly onto the knurled section on the spindle.

IT WORKS!

New belt £5 delivered
New stylus £10 -I ordered this before I repaired the deck, I might get a better one if the cartridge is still good

Recommendations for a stylus for a 270c cart?

Working Technics SL-B2 £15!
Thank you Hivemind.

Sam01
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Re: Technics SL-B2

Post by Sam01 » 13 Jan 2019 17:43

Hi guys,

I’m just repairing my Technics sl b2 as the gear has cracked. I’ve cleaned the shaft etc of old lubricant, what is best to use as a lube when re-assembling.

Thanks in advance.

musicmn
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Re: Technics SL-B2

Post by musicmn » 13 Jan 2019 19:10

Hi, IMO Super Lube grease works best in these mechanisms. Its available at most hard ware stores in small tubes which is more then enough for this mechanism. I use a small artist brush to apply it just remember a little goes along way.

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