sanyo m7900k motor adjust speed

[aus10whales]

hello all,

i recently repaired a sanyo m7900k boombox. new belts, idlers, general cleaning, etc. it’s all working perfectly now but the motor runs very slow. if i sync up a tape with a digital file, it starts going off track after a few seconds.

the issue is, per the service manual, “The speed can not be adjusted by means of motor in this machine.”

there is no variable resistor built into the motor, and when looking at the board that the motor is connected to for power, i cannot find anything there either.

is there really no way to adjust the speed on this thing? the slowness has made it basically unusable with cassettes.

any help and guidance is much appreciated!

thanks

 

[Daz 125]

there should be a speed adjustment pot on the motor..look at the back of the motor and u will see a hole..put in a small flat ended screw driver and gently turn clockwise. it should speed up. if not then turn it anti clockwise ..just go easy with it..u dont want to break the speed pot

 

[aus10whales]

there should be a speed adjustment pot on the motor..look at the back of the motor and u will see a hole..put in a small flat ended screw driver and gently turn clockwise. it should speed up. if not then turn it anti clockwise ..just go easy with it..u dont want to break the speed pot

hi, thanks for the response. usually that is the case and i have done that many times, but not for this boombox. the casing on the back of the motor is solid. i even removed the rear casing plate of the motor to see inside and it’s just the motor, no circuit board with a pot. the small board that the motor is connected to does not have a pot to adjust the speed either. unfortunately this is why i’m lost.

 

[Superduper]

Some boomboxes do not have any electronic speed control mechanism. The Sanyo M9998 is one of those which is puzzling, so your options are to ensure that the entire rotating assembly is cleaned and free of sticky gummy crap, and belts are correct (not loose, not over tight). If the speed still isn't correct, then you are looking at replacing that motor. On a positive note, the replacement usually will have exactly that same pot adjustment on the obverse of the motor like you are used to. The negative is that almost all new replacements are cheap chinese counterfeit clones that are inferior quality to the original and may exhibit unreliable operation.

 

[Daz 125]

hi, thanks for the response. usually that is the case and i have done that many times, but not for this boombox. the casing on the back of the motor is solid. i even removed the rear casing plate of the motor to see inside and it’s just the motor, no circuit board with a pot. the small board that the motor is connected to does not have a pot to adjust the speed either. unfortunately this is why i’m lost.

your right..according to the service manual its not adjustable..which means you need to replace the motor because yours has a centrifugal speed control on the armature..that means taking the motor apart to adjust the little screws to get the speed right..good luck with that as they are a pain in the arse to get right..