Need help fixing my Sony WM102 - it keeps loosing motor speed and kinda dying

Hi everyone,

about two months ago I bought a Sony WM-102 off of ebay with the intention to restore it into a fully working order. I've been slowly fixing it over time - I replaced the belt, cleaned all the flywheels so that it runs smooth, cleaned the capstan and the head, adjusted the speed and head alignment things like that. The only thing I didn't touch yet is the pinch rollers although I plan to replace them eventually due to the high wow and flutter which is probably caused by them.

Anyways, to the point - I managed to restore it into a working order where it can play tapes and it's listenable, not perfect, due to the aformentioned wow and flutter, but not bad by any means. It's getting close. Apart from the wow and flutter ( and a broken off diode which I failed to solder back on ), the only other remaining issue is that the player has problems with loosing motor speed.

It can play normally for hours, but then suddenly it starts loosing speed until it either runs super slowly or dies completely. This can happen when it's stationary, but it's especially prevalent when the player is rotated in some way I discovered. At first, I thought this was an issue with the battery case, it has a capacitor and according to the seller it's been sitting in a drawer for like 20 years, so I figured ,,ok maybe the capacitor has gone bad'' or maybe it's the pins being bent in a weird shape and not having propper contact, so I ordered a replacement capacitor and sucesfully changed it, I also alligned the pins better where the battery case is less likely to disconect if it's bumped or touched. And it seems to have resolved the issue ... for like 5 minutes, untill the same thing as before happened and the player started loosing speed again, so back to the drawing board. I was looking on the insides and removed the board and I noticed that if the board isn't making good contact with the walkman body, then the player doesn't play. I couldn't figure out exactly which part of the board is the critical point ( there is 4 holes for screws which I assume also transfer power, but I couldn't figure out which one, as sometimes having only like one touching meant that everything is working fine and other times having all four touching I couldn't start the player up at all ), but I thought that maybe it was the board being loose and not having propper contact with the body thus triggering this failsafe and not getting power to the motors, so I cleaned the contacts with isopropyl alcohol and made sure the board is secured tightly. For a brief moment it seemed like that resolved the issue, the walkman was running at the correct speed for like a day, irregardless of if I rotated it in some way or not, but then again the issues returned, even with the tightly secured board.

And I'm kind of out of ideas as to what could cause this - or rather, I suspect it's either some faulty capacitor somewhere on the inside, or maybe a cracked solder somewhere, or some issue with the motor, but I don't know how to find out where the issue lies. I'm not super knowledgable in electronics, so reading where exactly the issue is is difficuilt for me, not helped by the fact, that the components are on the inside of the board, which needs to be touching the body in order for the motor to run. I also don't wanna needlessly stick my screwdriver into places that don't need fixing and which I could damage accidentally in some way - like the motor ( which also seems a bit of a pain to get to ).

I'm hoping someone here could maybe know what the issue is or could be and point me in the right dirrection as to how to solve it. Maybe you came accross something similar yourself ? Any help would be much appreciated, I'm in a bit of a dead end and I don't know how to continue next.


Some additional information:
- Sometimes removing the battery box and placing it back again fixed the issue ( although I think that was probaly because I moved the player a lot, so maybe it got like re-alligned ? ).
- Usually, leaving it stationary and turned off for a bit makes it run fine again for some time, I don't understand why.
- The slow down when turning the player is pernament - what I mean by that is, that if I turn the player and it slows down, it doesn't go back to the original speed if I turn it back into the original position, it stays the same slower speed or slows down even further.
- Here are two youtube links showing the issue ( I'm turning the player on purpose to trigger it, but it's generally so bad that even just walking with the player causes it - kinda a problem for a device called walkman hehe ):
https://youtube.com/shorts/wR_T_9aEo5Q?feature=share
YouTube
https://youtube.com/shorts/LuLdfbcDOXo?feature=share
YouTube
- Hope I posted this in the correct place, new here, this is my first post apart from the introductions.
- I'll try my best to answer any questions, but please keep in mind I'm not very well versed in electronical engineering, so please explain things to me like I'm an idiot ( which in this case I am )

 

When the speed drops, the LED also gets dimmer ?

 

I have worked a number of these and this can be tricky. It does sound to me that the motor is struggling a bit even when you first hit play. I am not sure if this has been taken apart before you got it but there are white thrust washers behind the capstans and the centre gear that can disappear if you are not careful. There is a gear that runs off the centre gear (cream coloured) that controls the autoreverse. It can get sticky. Same with the tension pulley on the right (looking at the gears with the back off). The gears under the plate where the tape goes can also gum up. The pinch rollers can also push on a worn capstan and slow things down. Sorry that this is not super helpful but you potentially have a power problem (as per Valentin) or you need to clean and lube all gears, pullies, and potentially the motor.

 

Sadly, I can't really say conclusively, as the LED diode was already snapped off the board when I got the walkman from the previous owner. It was just taped there with a bit of duct tape and while it lit up occasionally and flickered a bit, it's really hard to tell if this was because of any power related issues or just the diode not getting a propper connection. I tried fixing it, but was unsucesfull sadly and now it doesn't work at all so can't really confirm.

 

It's possible that the motor is already struggling a bit - I'm not fully sure how it should sound when it runs without any issues, as I don't have a fully functional unit that I could compare it to. As for the rest - I'm fairly certain it's been taken apart before, as the diode was taped to the board, which tells me that the previous owner probably accidentally snapped it off so they probably did some repairs on the board.

In regards to it being a lubrication problem for the gears - I'm not so sure of that, for one I did try to generally clean and lubricate everything I got to - as you mentioned, it's all held by these tiny washers which are very easy to dissapear ( and not so easy to remove ), so I didn't want to remove anything I didn't strictly have to ( just for the record, no washers should be missing on this unit as far as I know ). The reason why I also think it's not the gears causing this, is because it runs fine for hours at a time sometimes - for example yesterday I was traveling to my country's capital and I took it with me so that I can listen to the music on the train and it worked for like 3 hours, switching tapes, reversing, autoreversing and playing the other side - it all worked fine and then randomly after like 3 hours it started to slow down, so I knew it was dead by that point. The machine has a mind of it's own I fear.

I think maybe removing all the gears fully and just taking the whole thing apart would probably help with things atleast marginally, but as I mentioned, I don't really wanna touch things if I can help it, just so that I don't loose some washers or break something by accident, since replacements are hard to get. In any case, thanks for the reply !

 

Ok, fair enough. From the videos it does seem that it does slow down when upside down and then the speed increases as you flip it back (although not fully). There is some level of gravity effect going on here. That is why I mentioned the capstan thrust washers (not the retaining split washers). The capstans are heavy and can rub upside if the thrust washers are missing. Same with the motor. If there is belt residue or hardened oil in there, something may rub differently inside when you move it around. You are right, it may be something else but something worth looking into unless you are going to find someone to work on it for you. Thank you.

 

I took the motor apart since it seems to be causing the issue. I'll try to clean everything as best as I can, but I want to ask - does anyone have any experience with how it should look ? More specifically the motor wheel ? It seems a bit worn to me, but I have no idea how it should actually look like, so maybe it's fine ? Any help would be appreciated.

Btw just for info, I did look at the washers, they are present and they don't seem to be causing any issues, the capstan wheels are rotating fine without any resistance.

 

dunno if the motor is the issue or elsewhere (like things needing lubrication, which would be really any of the spinning bits that ride in a bearing (motor, flywheels)), but it sounds like its drawing more current than it can sustain- which i literally just wrapped up another player with the same issue
capacitor you replaced was probably acting as a decoupling/filter, swapping out the old diminished one for a new one sorta delayed the onset of the problem but you didnt really fix the problem itself causing the capacitor to drain (decoupling = it acts as like a little battery for when load spikes happen, but it can also filter electrical noise n junk out and keep them from entering the main VCC(power) rail)
so honestly id try lubricating the things bearings if nothing else is glaringly wrong. get friction to a minimum = the motor wont have to pull as hard to spin
not an electrical expert so thats kinda my explanation of things to the best of my ability

thats what id try atleast, get yourself some moebius watch oil since this one uses lightweight parts (in turn the motor isnt super beefy), if you use oil thats too heavy itll only slow it down so you want some light stuff there

 

Quick update: After the cleaning and lubrication, it definetly runs smoother - or ran. It worked perfectly for about 5 minutes ? Then it started doing the same thing as before - that is slowly loosing speed and dying. Well, I guess it's not that then.

 

I tried lubricating whatever I can get to, the flywheels, the motor now, any gears, all of it. It's all working smoothly, there is nothing that feels like it gives any major resistance. For the first few seconds the motor even runs well, it just all works perfectly fine, then it starts loosing power. I don't know why. I checked and all the washers are there, as I mentioned I replaced the capacitor in the battery compartment, and it also doesn't help. I'm really just kind of lost as to what it could be. Maybe some capacitors on the board could be faulty ? The decoupling thing makes a lot of sence, even if the issue originally was with that, it probably uncovered more issues further along ? Hard to say, I'm not very well versed in electrical engineering either.

 

i would check the replacement you used was a 1500uf4v but id guess you did a 1:1 replacement there already so its probably fine
you could try measuring the motor voltage next- it should avg around 1.5v give or take according to the service manual (IC601, pin 20)-