Too high a voltage speeding up tapes?

[kb12]

Hi, I have a quick question... I have a reel to reel (Akai gx646) that is supposed to be powered at 100 volts (Japan), when I play it in the US at 120 it seems to be playing all tapes at a higher speed. Does this make any sense or is there something wrong with the machine? I know when I tested it in Japan it worked fine. Thanks for any help...

Kevin

[OthoV]

Japan uses 100v 50hz, US 117v 60hz. There should be plug that rotated to change the voltage and the drive belt moved to the other drive pully step to change the speed.

[kb12]

Mine doesn't have the voltage selector, its a japan only version I guess...

[louisiii]

A couple of things: first if the motors are 50 cycle (Hertz(for Dr. Hertz)) then 60hrz will make the motor armature rotate faster. This can be fixed if you can find an ARC RADIO cycle convert (US Army circa 1940). To control the voltage you can buy a VARIAC tranceformer used to control the speed of the motors for AC motors ( most electronic supplies and bio lab suppliers). If the motors are DC which I do not think they are (too costly) then they can be varied with an inexpensive pot (potentiometer; linear or rotary; a variable resistor (check to motor wattage to size the pots watts; you could generate some heat). There may be a mechanical idler pull and belt that can be adjusted for speed or change the size of the pulleys)). In any case a set of strobe wheels, variable strobe light, and a set of strobe tables are best to have. This will allow to clock the rational speed of your tape reels and allow you to visualise your corrections.
GOOD LUCK

[cbrworm]

Shouldn't the 646 have a servo controlled capstain motor? Do these use the A/C input frequency for speed reference?

I also thought they were direct drive.

I could see the voltage causing problems in other areas though.