New acquisition Sony WM-F702

Hey guys

Finally managed to pick up one of the Walkman models I’d always really wanted, a WM-F702, in fantastic overall condition, for £45.

Now of course it’s not working, and sadly did not include headphones, so I need to cough up for one of those slightly pricey little adaptors so I can use decent headphones with it. I think the cheapest i saw one of those was around £15 delivered.

So to the functionality of the player…
I knew the display was working at least, which has been a problem with similar models I previously got, and the tuner displays things correctly. That’s about as much as I know really.

I received it yesterday and the tuner controls work fine, although I can’t find a way to turn the tuner/display off as such. I haven’t put a a coin cell in it yet nor read the user manual so maybe it keeps display on with a coin cell in it, but deactivated the actual radio output with the radio off button.
Can’t check since I don’t have a headphone adaptor yet or know pinouts for the circuit to be able to hook up an earpiece directly.

Pinch rollers look like they need replacing and the belt was mush of course so removed that and cleaned it up.

Didn’t have the right belt so I ordered one but had one which I was able to fit just to temporarily try it.
Something I pressed made it whir and click with no tape inserted but I haven’t been able to repeat that, even after removing and replacing battery/tape etc.

With a tape inserted, it seems most keys are still only causing it to change the radio preset, and not try to play the tape or transport.

So I wonder if something is just not sensing that a tape is present maybe?

Anyway, I will rtfm and try to get a service manual then go from there! Really hope I can get this one working out of all of them.

 

These WM-700 series don't have a tape in switch, they should operate with the door open and no cassette inserted.

There are 2 main problems that need to be solved on your unit:
- checking if the table reels rotate freely: you should be able to rotate them easily by hand without significant resistance;
If that is not the case, the gears below (see picture attached) need to be cleaned of old grease and re-lubricated with oil.
It's a very common problem on these units, so don't try to use it without solving this as the gears may break.
- the buttons may need cleaning. Erratic behaviour like you describe is the symptom of increased contact resistance.
These buttons operate using a resistor ladder, so increased contact resistance will generate voltages outside the windows the microcontroller recognizes as a command.

 

Thankyou kindly Valentin, that's much appreciated indeed.
I did see the article mentioning this model in respect of cleaning the buttons' contacts as they can cause erratic behaviour. The information about the gears is especially useful thankyou!

I will try to investigate those points further this evening if possible. I didn't yet find a service manual for this exact model but I did get one for the WM-FX85 which I understand has a lot of similarities. It should be better than nothing anyway.

 

Well one of the table reels spins very easily but the other feels like it must be engaged and turning a mechanism as it has quite a bit of resistance like it is left in play mode maybe.

I'm not sure how to disengage that since the buttons are not really doing anything for the tape movement currently, so I think I should prioritise the button cleaning.
Will have a look for a guide if there is one for buttons removal/cleaning on this or similar but if not I will figure out. As long as I can put the parts back in how they originally were!

 

Look fot F701C or 701c service manual. Yiu should find it

 

You need to engage the solenoid with a pair of tweezers and then rotate the middle pulley clockwise. See picture attached.

But first I would check if the mechanism is really latched. That's simple to check, you only need to see if one of the pinch rollers is engaged.
Remove the belt and rotate the flywheels by hand. Do they rotate freely or one has resistance ?

I recommend only removing the metal top plate (it's soldered on 2 points), not removing the entire buttons PCB as that's unnecessary.
You can first try spraying some contact cleaner and press the buttons 10 times or so before even attempting to remove that plate.
I recommend Kontakt60 as contact cleaner. Don't use the generic WD40 type cleaners.

 

Thanks Raul, I will get one of those manuals you suggested then cheers.

Valentin, thanks for the description and picture. A funny thing happened because before I saw your reply I must have moved or disturbed something and now it appears that all the transport/play/stop/reverse functions are working ok without even cleaning it, and also the button to switch the radio off etc are working correctly.

None of these were working yesterday, but the only thing I can think that I have really done as such is that I am pressing the buttons without the case being attached at present, but also I had spun one of the wheels and I think something moved/clicked. So I'm unsure what the issue previously was, but now all of the functions of both cassette and radio appear at least to work perfectly well! Amazing.

So what I have to do next is order one of those headphone adaptors. I have no way currently to know if there is any working audio output yet without one of those, unless of course there is an easy way to get some earpiece wires soldered temporarily onto the board or maybe even a makeshift headphone adaptor perhaps. I wonder if I might be able to 3d Print a piece that will allow me to access the contacts in the headphone socket maybe for now, as it will take weeks to receive one of those adaptors if I order one today.

The other things I need to address though are the pinch rollers, so I will order some. Only one appears to have a dent in it from one of the capstans, the other looks ok, but I will replace both.
But also the motor and mechanism are noisy. The motor running with no belt attached sounds a bit rattley so I guess I need to follow the guides on how to lubricate the motor, but I think I also need to lubricate more of the tape mechanism as it generally makes quite a bit of noise, and sounds just rather dry I think.

Thankyou very much for all the info you've provided and the guides etc on here! I realise it's possible yet that this unit has no audio output or faulty, but I'm excited that the controls are all working now.

I was going to also say that it seems strange there is nothing on the LCD display when it is in tape mode and playing, but looking at the user manual now, it seems like the display is actually only used for the radio and not the tape functionality at all. Seems like a shame that it does not use it at all when playing tapes, and a little bit odd compared to other units, but I guess it's not a fault anyway.

One other thing that surprised me a little is to realise that this model is actually a year older than one of the other Sonys I have, the WM-FX70 (not fixed yet). I always thought that the 702 was a nicer model so it surprised me a little to learn it's slightly older, although I notice it apparently has a lower frequency response than the newer fx70 model too!

Anyway, I will order a headphone adaptor, and then go read the info about lubricating the motor etc and hopefully soon be able to have a fully working machine. It's in lovely condition too so even better.

 

Something is gummed up in the mechanism, likely the middle black pulley.

As far as lubrication goes, there are a couple of things that are a must:
- the motor; On this one it is simpler than what I show in the tutorial as it's put together with a screw, no glue at all.
- the gears near the table reels; even if they seem to move freely, I would clean the old grease thoroughly and replace it with oil;
- the middle black pulley; this one also has grease on the shaft which is hardened;
- the capstan bearings; be careful when removing the retaining washer as underneath there's a much softer one which can be deformed easily;

As for the audio part, clean the volume potentiometer with contact cleaner. Remove the wheel, spray cleaner inside, turn it back and forth 20-30 times.
Let it sit a couple of hours and then turn it again back and forth 20-30 times.

There are no common problems with the electronics on this one (apart from the buttons which seem to work in yours) and there are no electrolytic caps.
So if you re-lubricate the mechanism and motor, clean the potentiometer and put new pinch rollers you can pretty much expect it to work perfectly.
The capstans are to be checked, if there are rust marks (those will render high w&f) you will need to sand them and then roguhen.
Check post #29 here: https://stereo2go.com/forums/threads/list-of-walkman-portable-recorders-common-problems.7535/page-2

 

I just received some fresh supply of contact cleaner today so at least I can try this now.
I often use brake cleaner or carb cleaner for that task on more chunky switches but not for something this tiny and intricate.

I was looking at the back of the motor and realise I need to remove a ribbon cable from over it at the very least, or maybe remove the whole thing.
I have looked at the guide for dismantling the motor itself and lubricating it, which is very useful thankyou Valentin, but I need to look further for any info online that shows either removal of the motor itself from the player/chassis, or just the cable if that's the only access I need at the top of it possibly. From the guide though it looks like removing it entirely is the best option.

I have looked on youtube and google for any existing guides on doing that on these kind of model range but not found an example, so I will have to just figure it out and go very slowly and carefully, with lots of photos so I don't end up with something being a mystery for where and how it goes back again! Fingers crossed that I'll be able to do this correctly without any mistakes. I like taking things apart but I'm very aware these things are very delicate and intricate.

 

There is no guide online about this, I'm pretty sure of it.

You do need to remove the motor from the chassis. There are 2 ribbon cables that need to be desoldered: the DC-DC converter and the motor one.
You also need to remove the 3 wires (take a picture before) that go to these flex cables.
After the solder points are desoldered, the flex that goes to the DC-DC converter (below the motor) must be lifted together with the outer DC terminal (can be lifter with a pair of tweezers).
Motor itself is held by 2 screws in the cassette compartment.

In fact you can see in my previous post #6 that the motor is removed. If you need additional pictures explaining it, let me know, but I think it is pretty straight-forward to do.

 

Fantastic info again thankyou kindly.

First up, prior to trying to remove the motor I’ve applied minuscule amounts of oil (with a pinhead basically) to some of moving parts that I had visible access to, to see if this made any difference to noise. It has helped slightly but not a huge difference.

I discovered after a little while letting it run in different playback or ff/rwd modes (with or without a tape), that it would change suddenly from being a slightly noisy/ticky sound to a nasty loud noise so I would instantly stop at that point.

This was repeatable every attempt where it would operate reasonably normally (albeit with a bit of ticking from the mechanism) to then making this nasty sound after a minute or two. It sounds like dryness/vibration at high speed so I assumed this is the motor itself.

sure enough when I removed the belt then this noise begins instantly when the motor spins, confirming for sure it’s not the rest of the mech.

Anyway, reassured that I have a slightly useful advantage here in having a nice motorised desolder pump (one of those things you rarely use but are super grateful for when you need it), I’ve set to work removing the motor.

I was a little confused about the three wires you described until I realised my Walkman is different to your photo for some reason, and only actually has one of them! You will see in the photo.

I’ve successfully removed the motor now anyway thanks. I think I was of the mistaken impression that this motor type just opens up without removing glue, but that doesn’t seem to be the case as it does appear to be glued closed. *Edit* Just realised your guide does specifically include my model and does indeed say about removing the glue for this type, so I must have completely imagined any other way for this walkman.

I will carefully work through removing that as per the tutorial anyway (thankyou again!) and see how I get on.

Here are the pics so far…

 

Ok managed to get that apart seemingly without any damage (and amazingly didn’t slash my fingers to bits!), so I need to call it a night for today as it’s too late, but I thought it interesting to note discolouration inside the lid of the motor can, and on the top disc that sits beneath it.

I assume that’s from heat or contact between them, but hopefully doesn’t indicate it’s in a really bad condition otherwise.

Anyway, tomorrow after work I will oil/grease it as per the tutorial then reassemble and hope it’s better after that!

 

It's my mistake, I recently fixed WM-701Cs/F701Cs (so this is what I had in mind) which now I realise have a different type of motor than the WM-702/F702.
The 701C motor is held with one screw, while the 702 is glued as it's shown in the tutorial. In fact the pictures used in the tutorial are from a WM-702.
Think this also explains the difference with 1 wire vs 3 wires: the 702 has only 1 wire while the 701 has 3. The picture I uploaded is from an F701C (can be seen on PCB silkscreen).

In the big picture of things, it's not really a big deal as even the glued one is pretty straight-forward to disassemble as only the top metal cover is glued.
The WM-EX series motors are significantly more tricky to open in comparison, as on those the very thin PCB (with coils formed by traces) is glued on the edges.

About the discoloration, if it's just discoloration ignore it. But inspect carefully and make sure the 2 parts are not actually touching each other.
If there are scratch marks it means they're rubbing, but from the picture it looks like just discoloration.
Clean everything well: bushing, motor shaft, rotor, metal disc, coils plate, case. Then re-lube and assemble back.
Turn it by hand and make sure there is no metal to metal contact before glueing the top back.

 

Hey Mister X, thanks so much for that service manual link, I had looked for the correct one online and not found one for the 702, but had some other similar models, but that's great thankyou.

Thanks Valentin, yes the discolouration ended up removing easily with a cotton bud and some IPA, and the bud was pretty dirty afterwards. I was surprised because the marks had that discoloured look you get when metal is hot, but I guess it wasn't that since that sort of heat mark does not usually come off with a gentle clean.

So the motor is lubed and reassembled now, and soldered back in place. Happy to report that it is now way more quiet thankfully, so that has really been worthwhile.
So aside from the pinch rollers and still having no idea if this unit actually creates any sound yet (as I do not yet have a headphone adaptor) I thought, great, this is sorted now!

With the motor refurbed and new belt in place, all the controls were working perfectly, so I reassembled the rest of the player, and put the lid back on, carefully making sure the switches were all aligned properly.
And a strange thing happened. Remember when I originally said the logic buttons were not responding correctly and that all the buttons were doing the same thing? Well it was doing that again once reassembled, even though they all worked perfectly a few minutes before. I couldn't believe it!

So I messed around with it, and after a while I concluded something must be either shorting, or pressing down on one of the switches maybe when the cover is put back on and the screws fastened.
It did then at one point begin working correctly again, but overall it's being weird again after reattching the cover, so i think I will need to remove the cover again, and take a closer look for whatever is causing this to happen.

On the plus side though, at least the motor repaired ok so it's all good!

 

Well, exciting times.

I received the headphone 3.5mm adaptor at last today and can thankfully say this unit has no issues at all with the actual audio output. It is solid and seems to have a lot more power and body than I would have expected.
So that's great.

The cassette playback is very very wobbly/'watery' sounding so I would hope that might improve once I can fit new pinch rollers to it.

Aside from that, I noticed something odd with the FM radio, that the frequency does not seem correct. One of our local stations is on 97.2 mhz for instance, but I was receiving it on 98.5mhz somehow.

Good start though for sure!

 

Glad to hear it's working ! For my own curiosity, what eneded up to be the problem with buttons not doing anything ?

I definetely hope so, but more inclined to suspect the capstans themselves to be the actual problem. Check for any rust spots, these capstans are very prone to rust.
If they're rusted, they will need sanding (while unit is running), then roughening with ferric chloride. But some have deep rust (although by eye it looks superficial) and in some cases the capstan/flywheel assembly needs to be replaced.

This is caused by the FM VCO not being properly adjusted. See picture attached.
For this adjustment you will need a ceramic tip screwdriver and patience as this adjustment will drift as the circuit warms up.
So you need to adjust, leave the unit on for 30min, re-adjust. And it may take a couple of such adjustments to make it perfect.

 

Awesome info as usual thanks!

with regard to the logic buttons I haven’t actually done anything to it to resolve that, although I did spray in a little contact cleaner in situ and worked the buttons quite a lot at the same time.

They’re behaving ok for now so I’ll just see how it goes for now and dismantle more later if it becomes an issue again. I guess.

The capstans do not appear to have a very smooth surface from what I recall when I checked them but I need to look again. I remember thinking though that they’d been shiny smooth on other units I had and not on this.
Did not notice any rust but I haven’t looked closely enough yet.

I should have no problem smoothing them up if need be though as I have some very fine sanding cloths that go right up to 15 or 30 thousand grit, and lots of polish compounds. I do also have ferric chloride I think as well.
What is the purpose of using that? Is it to lightly etch the surface?

 

In regard to capstans, rust may not be very visible. You need to take a closer look and check for any dark lines/spots.
Move your fingernail across the surface of the capstan: it should not catch on anything. Unfortunately on these very small capstans any imperfection will cause wow&flutter.

The purpose of sanding is to make it flat again in case there are rust spots. I use 800 and 2000 grit sandpaper for this. No need for higher grit than this as the purpose is not to make it mirror finish, as you need to roughned it again anyway.
After sanding it with 2000 grit sandpaper it will be way too smooth for normal operation and tape with slip between the capstan and pinch roller as the capstan won't have enough grip.
This is why you need to make the surface rough with ferric chloride after this step.

The unfortunate part is there is a limit of how much a capstan can be sanded because after a certain point you will reduce its diameter too much causing a drop in tape speed.