Hi, I am repairing a Sony WM-2 right now and changed the belt with no problems. But there is one problem. When I plug in the second battery, the Walkman gears a immediately spinning around. Sometimes they stop and then start spinning again. When I press play, fast foreward or rewind, the red light switches on and the gears spin normally. What can I do? Regards Torsten
I haven't been inside that model but you may have shorted the battery wires when you put it back together. I'd open it back up and see if any loose wires got pinched and the insulation is opened.
I’m having this issue with my Aiwa HS-PX310 - when I find out why I’ll let you know. I’ve ordered new transistors as these tell the motor to run and can go wrong.
Hi, thank you for your answers. Yesterday I put the batteries into the walkman and it worked fine. I did nothing. Maybe the capacitors had to discharge. I really don‘t know. Today it still worked fine, I left the batteries inside since yesterday. Regards Torsten
Hello, today I heard a strange noise from my work bench. The noise came from the WM-2, it started spinning the wheels/gears by itself. Any further ideas? I hope it is no capacitor problem. Regards Torsten
Exactly what mine does / did. Like yours it semi-cured itself but then got worse - now it runs all the time. I've studied the circuit diagram for my machine and removed and swapped all of the electronic motor control components, however, they were from another machine so I'm not 100% what I put in was okay. Anyhow, the transistors are the most likely culprit if it's an electronics issue - I've ordered new ones. Your machine and mine are a few years apart but the issue could be the same as aiwa probably used the same componets.
I think I've cured the constant running motor. I replaced the transistors again but this didn't work - in fact one new one I put in did funny things to the speed. I then replaced the governor chip (see photo above - bottom right) - IC303 - AN6612S with a new one (they cost a few pounds each). This seems to have done the trick, when you look below you will see that it does have a 'start circuit' built into it. Does your WM2 have this chip in it? I'm no electronics expert but swapping the chip over wasn't too difficult.
Unfortunately today it started up again on it's own a few times then permanently...then it started playing hi-speed-dubbing speed with no response from the motor adjust mechanism. So I'm not there yet - I may have to look at the load adjust shown above...
@Kili1234 I suggest creating a separate thread for the AIWA HS-PX310, as it is less likely you'll get an answer here, because of the keywords used in the title. Let's clarify some things regarding this thread: there are 2 different walkmans which people are talking about: the SONY WM-2 and the AIWA HS-PX310. The 2 have absolutely nothing in common, so no point in comparing faults between them. The pictures above are from the AIWA which uses a typical AN6612 motor governor IC. What I can tell about it, is it's susceptible to reverse polarity and the motor won't run at all when that happens (assuming everything else is ok). A motor running all the time would point to a shorted drive transistor or maybe even the leaf switch staying pressed all the time. The SONY WM-2 uses a very different servo circuit (with feedback from an FG coil), using a custom SONY IC (CX891). In the case of the WM-2, the IC is powered through an 82 ohm resistor, so it has some protection against reverse polarity, don't know if enough not to burn it. In the case of WM-2, start by checking the voltages that are marked on the servo schematic.
I have had both of these issues in a WM-2 that I am rebuilding (the motor running by itself, and the high motor speed). The motor running by itself (also at high speed) turned out to be caused by on of the motor drive wires (RED/WHITE) being caught underneath the external power socket, the insulation getting cut by the terminal on the power socket, and grounding the motor wire to -ve battery. The motor in these units is permanently connected to +3v, and the negative wire is controlled by the servo speed controller. Shorting this -ve wire to the battery negative causes it to run. Regarding the motor running at high speed when PLAY/FF/REW is pressed, with NO response from the speed control pot. This turned out to be a faulty Tantalum capacitor (C601 in the above circuit) in the power supply for the speed controller IC. the Tantalum was pulling down the voltage through the 82 ohm decoupling resistor, and upsetting the speed controller IC. This also has the affect of dimming the red BATTERY LED near the play button. All the tantalum caps should be replaced. I am also having significant W&F issues from this unit. it has new belt and pinch roller, all mechanical bearing lubricated. I am currently in the process of replacing all the capacitors in the speed control circuit to see if its electronic rather than mechanical. I did find that the take-up reel tension was excessive - to the point whereby if you lifted the pinch roller from the capstan during play, the take up reel tension was enough to pull the tape through the tape path at high speed. Lifting the steel "washer" that compresses the take up clutch, that is held in place magnetically, and cleaning the clutch faces and (maybe PTFE??) slip disc returned the take up torque to something more standard. Still the high (~1%) W&F remained. It is interesting to note that the FG (Frequency Generator) servo feedback system for the motor speed control only acts on the motor shaft speed, not the actual capstan speed. this it to regulate speed changes through battery voltages, etc. Other influencing factors on the capstan speed (such as worn or lumpy belts/pinch rollers) are not addressed by the speed control system. However, and fluctuations FROM the electronic speed control system will directly affect the capstan.
Tantalum capacitors do indeed go bad (short circuit) sometimes, but this is not that common of a problem (not in general, it may be on this particular device though). I have seen even instances where an electrolytic went short (but it's extremely rare), causing no Vcc on the pre-main IC, hence no sound. In such cases, the shorted caps usually get warm or even hot so you can feel them with your hand. You'll also see an increase in current draw (hence a drop in battery voltage), which can be observed as you mentioned by a dim led. Of course everyone is free to replace all caps, including tantalums. If quality ones are used, there is obviously no problem in replacing. What do you mean by "steel "washer" that compresses the takeup clutch" ? Are you reffering to the nylon washer between the magnetic part of the clutch (which drives takeup reel) and center gear ? The high wow&flutter is of concern, 1% WRMS is extremely high (unusable), the normal value should be 0.2%-0.25% WRMS. A problem with the motor itself should not be excluded as a potential cause. There is a paper piece glued on the rotor, which sometimes gets loose and creates friction. The motor can be disassembled and repaired if that is the case, I will have an upcoming thread about that with pictures (will also link an existing one). I must also ask: did you install a high quality belt ? A cheap belt from a 50 belts pack will typically have 1% wow&flutter. I assume you have cleaned the pulley grooves well given other stuff you have done. As for belt-drive units, the FG coil is never put on the capstan because the belt is elastic and there would be delays in the "correction" applied by the feedback system, so it won't work. Capstan servo systems work only on disc-drive/direct drive units. So yes, such a system will not correct for mechanical problems like a loose belt or worn out pinch roller, but that was not the point of such a system to begin with. The servo is supposed to do the following: - maintain a constant speed independent of battery voltage (within a certain range obviously); - maintain a constant speed independent of temperature variations: that is why the speed trimpot is ceramic (low temp coefficient) and some servos have a thermistor; - maintain a constant speed independent of load on the motor (within a certain range): this can be done by measuring the motor current (without FG) or by measuring the actual speed (FG coil); The thrid aspect is intended for maintaining the same wow&flutter and speed on most cassettes, despite some have more friction between reels and slip sheets that others and despite of tape position: at end of tape, when reel is full there is more load because clutch is slipping more. Let us know what you find.
Hi Valentin, Thanks so much for the reply. Yes, I was also caught out by the bad tantalum in this case, considering it actually failed in front of me while testing the unit. It did give me hope that if one had gone very resistive, that others around it may also be in similar condition. I have ruled out (or thought that I had) any other mechanical sources of the W&F, so was turning to electrical. Interesting about the loose paper on the motor rotor also. this I had no idea about. If the tantalum replacement yielded no results, I was going to power the motor from an external supply, just to see if there was any change to the W&F. This would effectively eliminate the electronics, if the same W&F remained. The belt and pinch roller were both from Marian at FixYourAudio. I have rebuild a few cassette decks using his parts, and always been great quality. Yes, the steel washer I am referring to is the one magnetically held in place on the top of the center gear, that sandwiches that brown nylon washer (not sure if this was the source of the magnetism, or the bottom metallic surface was. I did clean the whole assembly, and then confirmed that the clutch was not the cause of the W&F by unloading it during play (removing the take-up spool from a cassette recorded with 3.15kHz, and letting the tape temporarily spool into the surrounding landscape). this allowed the take-up mechanism to rotate at full center gear speed. no change to W&F. I am assuming that this magnetic clutch assembly does not need lubrication between the surfaces, even though there was evidence of something in it when I cleaned it...?!? Yes, the scale on my W&F meter only goes up to 0.6% RMS, and its almost always pinned, with it coming back into measurement range about 30% of the time. Very audible. The repetition of the flutter is slow (or quick for wow), and is almost consistent with the rotational velocity of the center gear however. Confused. I will drive the motor with an external source to eliminate and electrical influence. Thanks again Valentin, look forward to seeing the thread on the motor rebuild. Steve **EDIT** Yes, all three brass surfaces were badly discolored, and even slightly corroded by the old gooey belt. they were all polished up with steel wool and all remaining evidence of the old belt removed from the inner grooves.
@Steve Caldwell Parts from Marian are of very good quality, those are out of the question to be the source of the problem. In regard to the motor itself, there is a better way to take the electronics out of the question: measure the voltage at the motor with a multimeter: you should see a steady voltage with only small variations at the second decimal (tens of milivolts). If you see high variations, it's clearly a problem with driving the motor. Powering the motor with external power supply I don't think is very relevant because that will eliminate all the servo action and the wow&flutter will be very high (because it won't compensate for any load variation). The clutch does not need lubrication, but given it's magnetic it won't make a difference anyway. What I do lubricate on these is the plastic shaft on which the clutch rotates, to minimize wear. Motor restoration thread (existing one): https://stereo2go.com/forums/threads/wm-3-tps-l2-wm-3-motor-disassembly-and-maintenance.7424/ Will add mine in the future and the link will also be availabe in the list in my signature.
Hello! I'm having the same issue with my wm-2 motor running. It was fine and then all of a sudden it won't stop running and the volume is incredibly low. I've checked all the electrolytic caps and they are within range. What else can I check? There's no flickering of the led and no pinched wires.
Capacitors are not going to cause such a problem, even if they were to be bad (which I don't believe they are). The first thing I would check is the leaf switch (S901), maybe it stays engaged all the time. Note that the auto-stop mechanism not moving freely may also cause the leaf switch to stay pressed. Given one of the levers in this mechanism also engages the leaf switch, this can be a suspect even if the latching problem does not occur. Link here: https://stereo2go.com/forums/threads/sony-dd-series-play-ff-rew-buttons-not-latching.7524/ The fact that volume is incredibly low may or may not be related to this problem. Does the volume change when rotating the potentiometer or it stays at a fixed level ? Is your current draw within specified values ? It should be 115mA during PLAY and 120mA during FF/REW.
Thank you for the quick response. I am looking now and when I press STOP or PLAY there is no change in the leaf switch. It only changes when I press REW/FF. I have attached a photo. The volume does change when rotating the potentiometer, yes. It goes from not audible to very quiet. I don't think the pot is the issue because when I initially was working on it, that was the only issue and I fixed it through cleaning and reflowing solder points. This issue only came up when I reassembled it for what was supposed to be the last time
