Good morning/afternoon and sorry for the long post.

I recently acquired a Sanyo M9935k boombox which would play cassettes slow and sometimes I had to help the motor start spinning by turning the spindles. I replaced the belts and
it basically played normal but about 4-6sec. slower on a typical 3min song compared to another boombox that I have. Yet, I still had to help the motor get started once in awhile. The motor has no way to adjust the speed and I can't find anything to adjust the motor on the boards.

Anyway, I had purchased a motor from Studio Sound Electronics at the same time I purchased the belts, installed it last night because I started to get some feedback through the speakers due to the original motor and now it is way way worse. The tape speed is so slow its ridiculous. Adjustment to the screw on the back of the motor does nothing in its 180 deg. turn. Now, before I go on, when I first pressed play the new motor was turning fast but in the wrong direction and would get a short burst of feedback through the speakers when I would push down on any of the cassette controls. Darn, I had plugged the (-) and (+) wires to the board incorrectly. I reversed them, started rotating in the correct direction but very very slow. I was also getting a constant low buzz through the speakers and whenever I would touch any metal on the box the buzz would go away. If I would untouch the buzz would come back. While trying to adjust the rear screw on the motor the buzz would also go away. The buzz is now completely gone, though. Don't know what happened there.

This new motor is a 9v 2400 rpm unit. It is getting about 10.26 v when in play. Did I mess up the motor? Is the motor not the right motor for this boombox? Where can I get the correct one? Was it defective to begin with?

I took the original apart, which should still kind of work, but the brushes and commutator look very worn out. Brushes look not more than 1mm thick at the thinnest part and the commutator looks about 1/8" worn down right in the middle. I can put some pictures up of this motor if need be but is this motor fixable via brushes and commutator? Doubt it. Is this motor's speed ajustable through any of the four small screws it has inside?

I know the easiest route is obtaining a correct aftermarket motor for my Sanyo but I have no idea what RPM its supposed to be as I can't find any info on the original motor or where else I could get the correct motor.

I need to play my tapes. Please help and thanks in advance.

Well bad news,

I had sent an e-mail to Studio Sound Electronics regarding a possible fault with the motor that I received from them. They responded last night and they said that their whole lot of the EG530AD-9F motors, which they tested because they were going to send me a replacement, were bad. They all ran slow and the speed adjustment did not work. Studio Sound said Mabuchi discontinued this motor and probably dumped their last batch, of bad motors, on them.

Anybody know where I could get a good working motor for my boombox? Studio Sound suggested putting the model of the motor on the net and hope someone else carries a good working one.

Hi Algeeba, I had the same problem with my Sanyo 9935. the motor was shot. I took it apart with a grinder. I think it was to do with the coiling why the motor was shot. Im not sure if that Ams? tracking system makes these motor more prone to failure in old age. Anyway i replaced the motor with a new 9 volt that i bought at a surplus store for 1 buck. I think it does not have a name, but if i go by the store this weekend, I will check (im to lazy to take apart my sanyo for the millionth time). But it works as good as new. Very simple looking one. Does not have the tracking thing in it. really strong with rw ff. I hope that helps a bit.

I appreciate that Themobcrew.

I was looking through the net and I found two companies that sell them cheaper than Studio Sound. One of them for $5 each w/reasonable shipping the other for $1.79 w/shipping unknown. I asked both if they were willing to test the motors to see if they were good but have not received a reply. The one w/shipping unknown I also asked how much shipping would be.

Themobcrew, did that motor have a speed adjustment screw on the back of the motor? Look forward to hearing from you and thanks again.

I can't remember if it had the adjusting screw in the back. I pretty sure by 90% it did not have it. I didn't go by the store this weekend where i got the part, but when i find out what i used i'll let you know. (but its a pretty basic no name model). My unit is in storage right now. I think i lucked out too. But when you took out the motor, you removed the + and -wires off the base of the motor? not the circuit board? I removed them off the base of the motor.

I took the wires off the circuit board so that I could take apart the original motor apart to see what was going on. Crossing the wires did not mess up the motor, though, as the tech from Studio Sound said all their motors showed the same symptoms as mine.

If you could find more of those motors that you found to have as spares, especially at that price, is recommended because 1. you know they work 2. if you order EG530AD-9F motors it is now obvious they are a hit or miss.

I ask about the screw because my boombox is about 4 secs slower than my son's boombox when playing a normal 3 minute or so cassette song and I would like to match mine to his. But it is not that bad, so if no screw than no big deal. I wonder if the motor you have is like one of those that is used for hobbies. Would I be able to find one at a local hobby shop?

Thanks again and I await your response.

Someone mentioned that there are fake motors on the market
because mabuchi discontinued some of there motors. they look the same as mabuchi but there
not mabuchi.

To get a good speed adjust you need to make a 60HZ test tape on a good tape deck.
Than use a analog AC meter to align the speed.

You can probably fix the new motor you bought off Studio Sound. There is a 4 pin motor control IC in there (not a normal transistor) and you've probably damaged it by reverse polarisation. I've fixed quite a few of these before. If you open it, let me know what chip is inside it. Maybe I have one still kicking around.

Cheers. roddy

Roddy,

I took apart the Mabuchi motor apart but I cannot remove the circuit board off of its plastic holder. I can only see the back of the board and it appears that I have to desolder something to remove it. What I can see through two hole on the board is the adjusting pot and a resitor. On the bottom of the plastic holder is the motor shaft bushing, the brushes and there is a number printed on the bottom of the plastic holder "JC03".

Transwave, can you please let me know what to do with the meter and how to calibrate using both the meter and tape?

Thanks all.

Connect the AC analog meter
one side to a speaker
the other to the 12 volt AC tranformer.
Play the tape turn the volume up a bit
Meter will move up and down
adjust for slowest movement.
Test tape can be 50 or 60 cycle.

You have to de-solder the 2 pins which go to the motor brushes. Should be 2 lug looking solder joints. Post a pic of the cicuit board and I can tell you what to unsolder.

Roddy,

the 4-pin chip has lettering: 9D2 (in small) and AN6651 (in large)

Ok, well done. Its an AN6631 motor controller. I'll have a look on Monday at work if we've got one. If not there available here still in Germany.

If you have a multimeter, check the pot (the adjustable resistior) to see that its not open cicuit. I've had that before on a new motor too.

Cheers. Roddy

Roddy,

it appears that the speed pot is open. At first I thought I was getting some resistance but now I am not. That "graphite" is not removable with a fingernail is it? I touched it with my fingernail and I thought I removed some and that's when I started getting no reading. Probably all in my mind but either way it appears to be open.

Would it just be easier to try my luck on obtaining this same motor from another company and hope they are good? It looks like they also sell the AN6651 chip for some 35 cents or so.

Its up to you...If the chip only costs 35cents and a new pot probably costs around the same, try and fix it. Like I said, I've had that before (an open pot) on a brand new motor. The company who sold it to me didn't want to believe me. Well at least youv'e learnt a bit about the motors now anyway you go.

Cheers. Roddy