Micro-Seiki MB-10 TT - Too Slow..!

[woodturner-fran]

The next section (45 rpm drive) is slightly narrower. It steps down in dia by about 4 mm from the lower section (90 deg edge on the step). This section is a "parallel cylinder", no "high or low spots"

well you might have answered that there. See the homemade pulley shown in the pic below. See the way its fatter in the middle and thinnner top and bottom - the motor angle is meant to be adjusted so that the belt rides on the widest part. But you seem to have that sorted.

Last thing I can think of:

Could you measure (accurately with a vernier callipers) the diameters of the drive pulley and the platter (where the belt rides) and work out the ratio of one to the other. So if the motor runs at 250rpm at 50Hz, the ratio of the pulleys should give you 250/33.3=7.507

After that I'm all out of ideas on what to do here....

Fran

 

[stoolpigeon]

At the risk of repetition, you cannot leave out the belt in this calculation.

sp

 

[makinson1]

Don't quite understand this. Doesn't the calculation depend upon the inside diameter of the belt, which is the same regardless of the outside diameter of the belt?

 

[stoolpigeon]

What you have to look at are the effective diameters of the pulley and hub driven by a flexible belt of thickness t.

These can be approximated as actual diameter plus 0.5 t on each side ie actual diameter plus t.

Now if pulley and hub are the same diameter there will be no effect but because the pulley is usually much smaller there is a relative increase in its diameter.

I measured a Thorens TD160 to have pulley approx 13.8 mm and hub approx 159 mm.

Motor speed is 375 rpm so no belt hub speed is

375 x 13.8/159 = 32.5 rpm

I don't have the belt but it is probably 0.5mm thick so with a belt effective hub speed is

375 x 14.3/159.5 = 33.6 rpm

Difference is around 3%

sp

 

[bergui45]

Hi,
I bought a replacement belt on ebay for my BL-10X and the speed was innacurate!
So i bought another one from another shop and it did the trick!
Check your belt thickness and stifness and use only one that's exactly the sma than the genuine part!

 

[bulgin]

Can you check the belt's deflection - somewhere between the motor pulley and the platter rim?

It should be +- 4 to 5mm before you start feeling some resistance. It's difficult to guess from hot as hell Cape Town but the Micro Seiki turntables are favourites here at chez bulgin.

bulgin

 

[DirkLerxst]

As this thread trailed off somewhat inconclusively, I wanted to add that I have just solved this exact same problem on my own MB-10 thanks to user Sreten who suggested a slight widening of the motor capstan. I applied a couple layers of wifey's nail polish and now it is sounding perfect again (though I still have to test it with a strobe disc to confirm). So happy to have finally solved this issue because like the OP I had all but given up on the deck and was ready to get rid of it.. So a big thanks to all especially Sreten for the input even though it is now a decade ago!