Sony WM-D6C wow and flutter when take up reel is full

Hi!

I've recently bought a SONY WM-D6C in excellent aesthetics conditions.

I've changed its belts, the pinch roller and the idler tyre, but I still have a problem with the wow and flutter.

When I play cassette from the start the wow and flutter is not noticeable but, when the pick up reel starts to accumulate tape, the wow and flutter begins to increase. No problem with FF/REW or autostop.

I could't find any threads with a solution and I'm completely defeated, what can I do? Could be a clutch problem? If yes is it easy to resolve (I'm completely new in the repair of Walkmans)?


This is the link of my SONY WM-d6c while it plays:



I thank you vary much and I apologize for the broken English

 

That wow and flutter is bad. You can try sending @Deb64 a pm on this site, she may be able to give you pointers she is very good with D6C’s.

By the way the track playing, is that Paul Simon – 50 ways to leave your lover ?

Don’t worry about your English, it’s very good and better than my Italian.

 

Thank you!! I'll try to write to @Deb64.

The track is, indeed, 50 ways to leave your lover by Paul Simon!!

 

Hi @Lucabere17 and welcome to Stereo2go.

I see that you have replaced the pinch roller. I think that your problem may be the new pinch roller sticking in the cradle. You may have a little friction between the pinch roller hub and the cradle.
When you fit the pinch roller, there should be a little bit of free play (axial play) on the pin, about 0.1mm. You should just be able to feel a little bit of free movement of the pinch roller along the pin.
In order to get this, I sand down both sides of the hub with fine wet and dry paper (320 grit or finer).
Also, when you have finished sanding the hub, you must clean the hub and centre hole very thoroughly. Also clean the pin and make sure that the cradle is clean. Any dirt or dust in the pinch roller mechanism can cause wow and flutter problems.
I have had this problem with one or two D6Cs in the past. Sanding the pinch roller hub fixed it and now I always sand the hub when fitting a new pinch roller.

 

Hi!
Thank you for your response!
I've tried it, I've removed the pinch roller, I've cleaned with IPA everything and the pinch roller spins freely with a little of axial movement, but the wow and flutter is still present (if I put a little of pressure on the pinch roller against the capstan the wow and flutter lowers. I'll try to do a video of it).

 

here is the video.
P.S. I know it's not the right way to open the walkman for replacing the pinch roller but I've followed the most idiotic video for replacing it because I can be idiot just as easily unfortunately.

 

In the two cases of this which I came across, freeing up the pinch roller solved the issue. In your case, there are two other things which I would check.
Firstly, is the capstan very shiny? The surface of the capstan should be rough. This can be done using Ferric Chloride. @Valentin gives more information on this here: Help Sony WM-EX1 functions not working correctly

Alternatively, it can be roughened using fine wet and dry paper (2000 grit). You need to be very careful doing this because you don't want to change the round profile or put any flat spots on the capstan.
The other item I would check is the pinch roller pressure, using a spring balance. Instructions for this are given in the service manual.

Are you getting this problem with any other cassettes, or just this one?
The tape pancake on the cassette does not look very even, so the tape may be sticking. It may improve if you fast forward and rewind the tape through a few times.
It is also possible that the tape has become very slippery over time. I have a few tapes, where the tape has become so slippery that the capstan and pinch roller cannot grip it. These tapes won't even play on a twin capstan Revox. Depending on the severity of the condition, some tapes start wowing at the begining of the side and others towards the end of the side (where the pinch roller and capstan have to exert a greater force to pull the supply side spool round, due to the smaller diameter of the tape spool on the supply side).
If the tape is super slippery, you can make the it playable for about a week by baking it. I use a food dehydrator for this. I find that baking tapes at 60 degrees C for around 10 hours overnight works well. Do not try and bake your tapes in a normal household oven; the temperature control is not accurate enough.

 

The capstan looks a bit shiny but, to me, looks like the capstan from another D6C that I have that works perfectly. I'm attaching 2 photos so you can look at it.
I've never tried to rough a capstan, I'll look into it nonetheless!

Unfortunately I don't have a spring balance so I can't check it now. If the pinch roller pressure is low how could I increase it?

This problem appears several tapes that I own, both pre-recorded and new blank cassettes.

 

Here's a better look of the capstan

 

Capstan does look a bit polished where the tape rides. I would recommend to roughen it, as if you do it right there are no downsides.
Important point is (regardless if you do with sandpaper or ferric chloride) to do it while capstan is rotating, otherwise it will get out of round.
In the case of D6C, put the unit in REW (so auto-off doesn't trigger) and work on the capstan.

As far as the pinch roller pressure goes, a rough way to test is see if touching it with your finger can easily stop it.
Be sure to clean it with IPA after this test to remove any oil from your skin.

 

Ok I’ve ordered the ferric chloride and I’ll try it!

in the meantime I was looking at the mechanism one more time and I was wondering: should this metallic part be twisted like this? Could this be the problem?

 

The part you have shown is part of the recording latch, and is nothing to do with the pinch roller and capstan mechanism. It does not affect the speed of the tape.
These parts often look twisted. I think they are twisted in the factory as part of the adjustment of the recording latch mechanism, during the test and set up process.

 

Okok, like I thought

 

I've tried to clean up the mechanism and oil it and I think I may have found the origin of the problem: the play idler tyre. it moves with high friction (I've wash the shaft with IPA and I oiled it) especially with the washer on top, sometimes it even stops or slows down. The idler tyre is new (I've bought it from fixyouraudio.com).
I don't know if the problem is the type itself (seams to be the exact size of the original one), the clutch or the black gear connected to the capstan via the belt.
I've cleaned that part of the mechanism with IPA (I didn't disassemble the clutch, just the black gear and the idler tyre itself) and I oiled it but the problem isn't solved. Should I trim down a little the idler tyre?

Here's a close up video, at the end it really slows down:

 

No, I wouldn't trim the tyre.
I don't think this is causing the flutter. I don't think the tape is playing noticably slower at the end of the video than it is at the start.
The smaller idler tyre drives the take up spool. The black gear drives the idler and also the auto-stop gear.
The auto stop mechanism is driven, in turn, by the two white gears to the right of the idler in your video.
The two autostop gears can sometimes become slow or stuck due to the grease used on them becoming sticky and hard over the years. Normally this will stop the auto-stop mechanism from working and can stop the take up spool from turning. In bad cases, the capstan still turns, the belt slips because the take up spool does not turn and the tape spills out of the cassette at the capstan.

At this stage, I would wait until the ferric chloride arrives and then sort out the capstan before trying any other remedies.

 

In a couple of cases it happened that the take up spool completely stoped causing the tape to be chewed up by the pinch roller.

I’ll wait for the ferric chloride to arrive before doing anything else like you suggested.
Thank you!!

 

In regard to the small idler, what I have noticed can happen sometimes is the metal shaft can get pushed further down on the plastic lever when installing the top washer.
Hence why it's a good idea to check this idler rotates freely before getting over it. If it doesn't use an angled pair of tweezers to pull on the idler hub up a bit, until you have some up/down play.

While I don't think this is the source of your problem either, it's something easy to check.

 

The shaft was, in fact, a little pushed down, I lifted it but, like you said, the problem isn’t resolved. I’ll update once the ferric chloride arrives!
Thank you

 

I assume you've looked at the reel gears that drive your take up spool. It is common for these to have almost invisible hairline cracks in them which are OK until that spool gets to a certain weight and then you get a slight jerking motion on that spool. I realise this is past the head and pinch roller location but it doesn't take much vibration before you notice it in the audio output.

 

There is a thread about the clutch gear crack here: https://stereo2go.com/forums/threads/tps-l2-broken-clutch-gear.9534/
If the small idler is not slipping and takeup torque is very low, one can assume there are cracks in the gear, case in which it must be replaced.