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Akai ap b20 slowing down

Posted: 12 Aug 2019 01:03
by Pesceabrodo
Hello,

I am having a problem with my akai ap b20, it seems run too slow. I tried to change the belt but nothing changed, do you know if is possible to regulate the speed ? I also noticed that the capstan probably is too low to the level of the belt? Do you have any ideas ?

Thank you so much,
Pesceabrodo

Re: Akai ap b20 slowing down

Posted: 12 Aug 2019 21:05
by musicmn
Hi, from the info I have been able to find online this turntable uses a AC motor to spin the platter. This turntable does not have any pitch controls for the platter speed. The platter speed is regulated by the platter belt. It is very important that the platter belt has the correct thickness and width. A belt that is to thick and to wide will cause speed issues and a belt that is to thin and short will also cause speed issues. But before you go and order a bunch of different size belts make sure you have at least serviced the motor and the platter spindle. If the motor and platter spindle have old lubricants or no lubricant in them this will cause all kinds of speed issues. For the platter spindle it should be removed from the spindle housing. The spindle and inside the housing should be cleaned of all old lube. Then fresh sewing machine oil put back into the housing so the spindle can turn freely and easily. The motors bearing should also have fresh sewing machine oil put into them. By now the motor is usually dry from any oil. It's very important that the lower bearing in the motor be oiled. With out oil the rotor shaft can burn and this will cause slow speeds or uneven platter speed. Service both the motor and platter spindle then check the platter speed and see if that helped the slow speed issue. Let us know how it goes.

Re: Akai ap b20 slowing down

Posted: 14 Aug 2019 01:30
by Coffee Phil
Hi Pesceabrdo,

Welcome to the foum.

+ 1 to what Musicmn said.

In addition to that I’ll add a bit. The belt should run with the high spot in the middle of the belt. If the motor is mounted on grommets check the condition. Also check the alignment and operation of the speed change mechanism.

How slow is the speed? If everything looks correct I can believe 5 to 6 % could be due to the wrong belt. It is highly unlikely the the motor is off speed but it can be checked with one of those little optical tachs available on Amazon for ~ $15 USD. The speed on 50 Hz should be 1500 RPM. As musicmn said the belt is critical to speed. The effective radius of the capstan included ~ 1/2 the belt thickness. You machine has a high speed motor by today’s standards. That forces a very small capstan so the belt is especially critical.

After dealing with the cleaning and lubing if the belt is running in the correct spot it may be a good time to invest in the little tach before starting the belt search. Here is a link:

[url]https://www.amazon.com/s?k=optical+tachometer&crid=OLGIEBIRRR0J&sprefix=Optical+tac%2Caps%2C228&ref=nb_sb_ss_i_1_11[/url]

If everything checks out, you need the correct belt. Put real effort into that search as it may not be easy. I actually had to grind a belt to speed for my Rec-O-Kut Rondine 2 as at the time a belt thin enough was not available. The belt on the R-O-K is around the platter so while it was a rubber dust mess, it was doable. Grinding the belt on your machine will be a good trick so you may have to construct a fixture with pulleys and a motor to do it off the machine. It will be worth the effort to find the correct belt.

Phil

Hello,

I am having a problem with my akai ap b20, it seems run too slow. I tried to change the belt but nothing changed, do you know if is possible to regulate the speed ? I also noticed that the capstan probably is too low to the level of the belt? Do you have any ideas ?

Thank you so much,
Pesceabrodo
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