That leaf switch in your picture should be engaged in PLAY mode and disengaged when in STOP. There should be another leaf switch near the pivot point of the center gear arm, that is for FF/REW. Check that as well, if it's properly fitted, if it engages/disengages properly. According to the schematic, the 2 switches are in parallel so if any one of the 2 is closed, the unit will be powered on. I'm not 100% sure the schematic in the service manual corresponds to your unit and there is also a possibility that the FF/REW switch engages the motor, but also the muting circuit. If that is the case, an always closed FF/REW switch can explain both the motor always running and the low volume. From your picture I can see 2 wires going to a second switch, so a switch is there. And given your wires colors do not correspond with the service manual, I incline to believe what was stated above.
You're correct - I see there is another leaf switch. I guess the switch I showed you in the first photo is FF/REW because the gold one under the play button does in fact engage when I press PLAY and disengage when I press STOP. So if both leaf switches are working as intended, what could be causing the motor to keep going?
Yes indeed it is correct, the 2 switches are the other way around. You need to start diagnosing one thing at a time. Start by desoldering the wires from the 2 switches (the end that is connected to the PCB) and observe if there is any difference. If motor is still running measure the resistance between the 2 points on the PCB and see if you have continuity (with batteries taken out). If so, checck the PCB for any solder bridges. Is the tape speed normal ? Does the tape speed trimmer actually produce a change in the tape speed ? If tape speed is normal and trimmer does produce a change, then the servo circuit is working properly. If you were to remove the PLAY leaf switch and put the unit in play, does the unit run at normal speed or not ? I'm interested to know an estimate, like if it's going significantly faster or significantly slower (by eye). Also, when the unit is always running, is just the motor always running or both the motor and the amplifiers ? Meaning do you hear noise in the headphones (assuming no cassette is inserted) ?
Thank you! I will check tomorrow when I have daylight and get back to you on most of the details. The tape speed was normal according to what I had set it to, but I will check tomorrow to see if the speed trimmer still works. When I did have a cassette in, there was no sound when it stopped, only the motor running.
Ok, so let's take it one step at a time. The entire circuit is ground switched: the 3V is constantly connected, while the leaf switches connect or disconnect the ground. Given only the motor is running, but not the amplifiers, it means the ground side of the servo circuit is somehow constantly connected to ground. Looking at the PCB diagram the ground is common to both the amplifier ICs and the servo IC, so I don't know how the motor is always running, but the amps are not. This does not make sense, unless the amps are working, but at a very low volume. So please start by desoldering both leaf switches (at the PCB side) and see if the problem persists. If problem is still there, you can eliminate the wires shorting to the chassis as a potential culprit. Take a look yourself at the service manual diagram and schematic and try to figure out how ground is still connected to the servo circuit, despite leaf switch is open.
Alright, so I disconnected the leaf switches from the PCB and the motor continued to run. I checked and there is continuity between the two points for the PLAY/STOP leaf switch. I am confused because they are rather far apart so I don't know how they would be bridged? But I am out of solder braid right now and will have to wait for more to come in the mail before cleaning up the board. The tape speed is now very fast but I can not hear anything at all. The speed trimmer does not seem to have any effect any longer.
You need to check the PCB throroughly and see why there is continuity between those 2 point, because it shouldn't be like that. Tape speed very fast and trimpot not doing anything can mean a couple of things: - the servo IC is not working (output stage is shorted); - one of the drive transistors outside the IC is shored; - there is no FG signal going to the servo IC; - motor is somehow connected directly to the supply, bypassing the drive transistor (a potential bridge somewhere); In regard to FG, the resistance of the FG coil should be a couple of hundred ohms (don't remember the exact value). So you can desolder the 2 purple wires and measure the resistance between them. If it's an open circuit or very high resistance, you have a problem. In regard to the PCB do make sure there is nothing conductive on the surface of the board: measure on a place where there is no solder mask and see if you have any resistance.
Thank you, Valentin. Once I get my solder wick I will see what I can find. The strangest thing is it was working fine until the last time I closed it. Hopefully nothing is beyond repair
Ok, I got my wick and cleaned up the board! Progress in one place. It is no longer running without reason and there is no longer continuity between the leaf switches. Now we are here: - still no sound -there is a clicking noise when I hit play - FF and REW don't do anything. I don't see any cracked gears but I also don't know how they would have cracked between now and last time anyway. I measured between the FG points and got 07.40-1.12
1. Does the motor still run at high speed/trimmer pot not doing anything ? 2. Between FG points on the motor or on the PCB ? The reading is in ohms or kiloohms ? Please state the measurement unit as well, as a number doesn't tell much. Let's focus on these 2 first. The FF/REW not doing anything probably means the FF/REW leaf switch is not closing or there's a broken wire. You have the full plastic gear on your WM-2 and that type doesn't crack. The only gear that can crack on your unit is the small reel gear attached to the supply reel. Did you disassemble and re-assemble the mechanism in the meantime ? Please state in more detail what you did, cause from your description things start to break out of the blue and in reality there is a cause for these (and the aim is to found out what that is).
Thank you for your reply - 1. The motor doesn't seem to be running high speed. Speed trimmer is still not affecting it visually, since there's no sound I can't really tell. 2. The reading was between the two FG points in M Ohms. Visually, the FF/REW leaf switch is making contact and closing. I will re-solder the wires once again. I have not disassembled anything besides to access the PCB. It's why I am so lost and why I imagine it's electrical and not mechanical...
If the FG coil reads in the mega ohms, then it's open and that is what is causing your high speed and trimpot not doing anything. Even if you have measured in circuit (with wires still soldered), you should get a much lower reading. But to be 100% sure, confirm what resistance you are getting when measuring out of circuit (with the 2 purple wires desoldered). What I am interested in is the resistance of the coil itself (meaning measure at the open end of the 2 purple wires), which is inside the motor. With FF/REW, check the continuity: do you get continuity at the PCB when FF/REW are pressed ? If not, check continuity at the leaf switch. If you get continuity, one of the wires is broken. In regard to the no sound situation, what is the current consumption of the unit when in play ? You should get about 115mA. Let's forget about the potential mechanical issues like clicking noise and other things for now and focus on the electronics problem.
> My initial reading was actually with the wires desoldered. > How would I measure at the motor? It doesn't seem to be possible to open the motor up unless I am missing something. I would not be surprised if the wires are broken inside. The wires in this unit are very soft and deteriorated. Some of them had come off when I first bought it and had to be resoldered on. I also had to replace some wires with new wire. > I do get continuity at the PCB when FF/REW are pressed. I do not get continuity at the leaf switch. > I am not sure how to measure power consumption, what points do I measure?
Ok, if the reading was with wires desoldered then you have an open FG coil. The 2 most likely causes are the wires themselves (given what you say about the general condition of wires) or the point where they are soldered onto the coil itself. The motor can be opened and fixed, however it's not something I would recommend if you haven't done this before. Here you have a tutorial with the disassembly of the motor, look and decide for yourself: https://stereo2go.com/forums/threads/wm-3-tps-l2-wm-3-motor-disassembly-and-maintenance.7424/ From what I remember there was another thread with repair of FG wires, but I don't know what the title was. Ok, so you do get continuity at the PCB when FF/REW is pressed, but not at the leaf switch ? That doesn't make sense. Please double check your measurements. For power consumption measurement, you need to wire the multimeter in series with the battery terminals and power the unit from an external supply. You will need to switch the positive lead of your meter to the dedicated mA/A position. Given what you say with wires, I would double check on those, as these may be the cause of some of your intermittent issues.
Yes, I agree, I don't think it's worth opening up the motor. You are correct, I am getting continuity at the leaf switch! My probes are not very fine so I think they were placed incorrectly. In this case should I try replacing these wires with fresh wires? And if that doesn't work, maybe I will be forced to delegate it for parts since I don't want to go into the motor :/ Unfortunately I do not have an appropriate external power supply to test the power consumption.
Ok, so you are getting continuity at the leaf switch, but not at the PCB ? If so, the wires are the problem (which would be the first suspect anyway given what you stated before). Check the continuity of the wires themselves and move them around to see if you get an intermittent connection. Looking at the picture you provided in post #22, I cannot see anything obviously wrong with the wires: they don't look corroded, their isolation looks good. That is why I suggest to do more measurements before drawing any conclusion. Take it in a logical way: the switch needs to close the circuit between those 2 point on the PCB. There are only 2 things that can cause an open circuit: either the switch itself does not close (it's a good idea to clean those leaf switches by the way) or one (or both) of the wires is broken intermittently. So please do more measurements and try to figure it out more yourself, as thread already has a lot of posts without bringing too much useful information to others reading it. At this point I don't know if it's even worth pursuing this repair further as the MNF-1600B motor is pretty expensive and any potential donor unit to have this motor (TPS-L2, WM-2, WM-3, WM-5, WM-7) are even more expensive.
