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Correct Belt for Technics SL-B303

Tucker99

Tucker99

Super Member
AKer ETLS has a problem. He needs a new belt for his Technics SL-B303 and is getting some differing info as to the correct size.

So, from ETLS "[I have a ] Technics SL-B303... I have found that many different sites list it at either the 21.6", or the 23.6". With my own test, I found the total circumference to be 25.5."

His test was a manual measure using a length of speaker wire.

I want to assist and am about to flip him a 23.6" but if he is correct in his measure then the 23.6" won't work.

Anyone actually know the answer??

Thanks gang.
 
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Thank you for helping me to figure this out. Here's one site that shows the 21.6 for the 303.

Belt FM 21.6
Belts are shipped with installation instructions.

This one doesn't show a size...

This one shows
Technics SL-B303 FTBM21.4

and this one 23.6
 
How did the tension feel? Did it feel right, too tight, I doubt it felt loose...lol.
 
What sort of measuring did your friend do?

I have yet to encounter a Technics belt drive that didn't use a 23.6" belt. Not saying none exist but I have yet to meet one.

John
 
Pulled length of thin wire around platter and through one of the platter holes, held tension while putting platter back on spindle, using the two finger holes. I made sure that I held the wire tight enough as to not slip off the platter, and pulled the two ends around the drive motor, marking with a sharpie the intersection. Then measured the length of the two points, to get a total length of 25.5 inches.
 
ETLS said:
How did the tension feel? Did it feel right, too tight, I doubt it felt loose...lol.
Click to expand...

Concerning the 21.6, it didn't seem excessively tight. But, in searching for the part number SFGB321-1, I did run into a number of sites that featured a 23.6 belt.

This thread does spark some curiosity about which is correct. If a 23.6 can drive well with obvious less strain on the motor shaft it may be the better choice. I am curious enough to get one and see what happens.
 
ec1st said:
Concerning the 21.6, it didn't seem excessively tight. But, in searching for the part number SFGB321-1, I did run into a number of sites that featured a 23.6 belt.

This thread does spark some curiosity about which is correct. If a 23.6 can drive well with obvious less strain on the motor shaft it may be the better choice. I am curious enough to get one and see what happens.
Click to expand...


And, that is the cause of my concern. Would the smaller belt put undue strain on the motor, bearings, or the motor mountings? How much quicker would the smaller size belt wear out? Is the 23.6 "loose" enough to cause slippage, either while running, or slip off the platter on power-up or power-down?

While I could run either, I don't want to subject the turntable or any of its components to premature failure. Certainly, someone has the definitive answer to this question as to which size is called for by the manufacturer.
 
ETLS...

You measured 25"

I, and others, think the Technics generally run the 23.6.

I'm just gonna send it to ya...I pretty confident on this one. A TT belt needs to be a bit snug only, not all tight and stretched like an elastic.

EDIT ADDED...In an envelope ready to post...Will take a few days to arrive from the Great White North!
 
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I've never tried the measuring method you describe. Actually, I'm not sure what can be learned from it unless you had some sort of spec or knowledge concerning the optimum amount/percentage that a belt should be stretched when installed.

One thing I've noted, however, is that the correct size belt should be just barely shorter in length than the "race" on the platter, just enough smaller to prevent the belt from falling off. It should require just a tiny amount of stretching to install on the platter. This isn't very scientific but it's my observation with belts from 23.6" to 35.1".

I just measured the race on a JVC turntable I have which uses a 23.6" belt. It measures 24-7/8". That means the belt is stretched about 1-1/4" (around 5%) during installation. Another measurement that would be important is the distance between the center of the spindle and the center of the motor capstan. On the JVC that's just a hair less than 4-3/4" without the belt installed. (Installing the belt pulls the capstan about 1/16" closer to the spindle.)

John
 
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Thank you very much Tucker, a very generous offer that will certainly be put to use.

Boreas, the race measured 24 and three quarters of an inch, and the distance between the center of the drive motor shaft, and the turntable race is only a half inch. That's why I was in a conundrum as to the proper sizing. Thank you all who have helped to shed some light on this problem.
 
ETLS said:
Boreas, the race measured 24 and three quarters of an inch, and the distance between the center of the drive motor shaft, and the turntable race is only a half inch. That's why I was in a conundrum as to the proper sizing. Thank you all who have helped to shed some light on this problem.
Click to expand...

Okay, I just unpacked an SL-B3. Too lazy before. The measurements you came up with for the SL-B303 are the same on the SL-B3. I've got a 23.6" belt on it and it works fine.

Turntable basics says it takes a 22.4" belt. It also says, as you know, that the SL-B303 rakes a 21.6" belt. Why 2 turntables from the same manufacturer, with the same critical dimensions and measurements, would need different belts makes no sense to me. I'm thinking maybe TurntableBasics' info is in error.

John
 
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That's what I suspect as well, it didn't make sense to me why there wasn't more conclusive data out there on the web. I certainly didn't want to subject the motor to torque specs above its capacity and put it to an early demise.
 
ETLS said:
That's what I suspect as well, it didn't make sense to me why there wasn't more conclusive data out there on the web. I certainly didn't want to subject the motor to torque specs above its capacity and put it to an early demise.
Click to expand...

Side loads on the capstan bearing would be the worry for me.

John
 
boreas said:
I just unpacked an SL-B3. ... I've got a 23.6" belt on it and it works fine.
Click to expand...

I think that is the bottom line.

The 23.6" is posted and en route. You will see it in a few days time, well probably a week given the caliber of Canada Post!
 
Thank you Tucker99 you're awesome!! :thmbsp:

John, that was my worry too, not to mention a short belt life as well.
 
I used a 23.6 on mine, worked fine. Most Technics and Pioneer use this size. There's the Karma...

Thanks,
John.:music::D
 
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Hi guys, I just bought a REK O KUT B12H tt. What will be the best tonearm and cartridge? It comes with the S220/120tonearm and a Stanton 380A cartridge. I already have a Grado statement mm cartridge and plan to build a slate plinth for this tt. Thinking about $1k for a 12" tonearm. Any suggestion ? Thanks, Tam
 
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