Sony Walkman WM-2 Wow and Flutter issues

[Walkmann]

Hi All,

have moved on from fixing my old D6C to a WM-2 that I have just acquired.

It was sold as spares or repair and so I was not expecting a pristine unit. Anyway opened it up and replaced the belt, soldered the loose wires, fixed the DC input plug and repaired the broken circuit board, generally gave it a clean etc etc. All tested OK and worked to an extent. Set it up on the test cassette for speed/W&F etc and it came in at 0.5% wow and it has to be said on most types of music and vocals you can hear the WF. The motor speed is constant and adjusted to as near to pitch as I can get with the small pot.I have done all I think I can but there is one area I have not really looked at which is pinch roller capstan unit. The capstan is clean and is looking polished. I am loathed to use grit on it as suggested by others.

Has anyone experience of this unit and can maybe point me to any common issues?

Thanks in advance

[Ted Kendall]

What is the state of the pinch roller? You may be getting tape slip. The other thing I'd look at is take-up torque. Grit will just land you in more trouble.

[stevehertz]

Is there any opportunity to use some very light sewing machine oil in places where it may help? Motor bearings etc? Administered on the end of a pointed awl. Otherwise I clean my pinch rollers by taking a suitably doped cotton bud across them at 45 degrees. This both cleans and rotates the roller at the same time.

[Walkmann]

thanks for the replies, appreciated.

I have actually used watchmaker oil on all the bearings I could reasonably get to, obviously not all as I would have to strip the walkman fully down but the main ones I could get to. Could be the unit is slightly seized with age but the motor speed is constant which to me would suggest that the main mechanisms are OK.

I think the pinch roller is OK, it has been cleaned and looks and feels ok but could be slipping only a change of roller would confirm I suppose - may do that.

Interesting re take up torque, how do you assess that.

And suspicions re grit confirmed

[TIMTAPE]

A way to roughly test for tape slip because of a poor pinch roller or weak pinch roller pressure is to assist the pinch roller pressure a little and see if the problem improves, or in the opposite way reduce the pinch roller pressure a little and see if the problem increases.

A pinch roller should be firm but compliant. If you indent it with a fingernail the rubber should compress but spring back to normal shape immediately the pressure is removed.

Service techs use a cassette like torque gauge to indicate take up tension and back tension.

If take up tension is so severe that it is causing speed changes, test at the beginning of a tape side, and then at the end of a tape side. Because of the much greater tension the speed change should be worst at the beginning. So (all things being equal) the reduced tension at the end of a side should also reduce the speed irregularity.

There should be only a little back tension from the supply table. Sometimes oil or grease in the supply table bearing dries out and increases back tension. If so, the table can often be removed for cleaning after removing whatever circlip holds it in place. Test for back tension in play and also in fast forward by gently turning the table with fingers and use a similar machine for a reference.

[unitelex]

I would also check
1. Pinch roller spring pressure
2. Pinch roller face flatness (barrel distortion)
3. Replacement belt is of suitable size and good quality (consistent cross-section).
4. The flywheel/capstan bearing. Check for wear add play

Best Regards
Chris

[Reelman]

One problem I had that could explain your W/F is a very slightly bent capstan. Goodness knows how it happened but it was on a small Sanyo Radio/cassette.
Peter

[unitelex]

Also, check the motor pulley and flywheel pulley groove for any debris / remains of the old belt.

If the mechanism had been left for a long time in the "play" position then there could be a groove in the pinch roller where it had been in contact with the capstan. This is a common issue for older reel to reel machines, unlikely for cassette though - worth checking.

If you can determine the frequency of the wow/flutter it should point you towards the likely cause. Higher frequency flutter is usually motor or motor pinion related whereas lower frequency wow is usually flywheel capstan or tape tension related.

Chris

[TIMTAPE]

Originally Posted by unitelex

.. 2. Pinch roller face flatness (barrel distortion)...

. Some pinch rollers are meant to be flat while others deliberately convex. Studer Revox used convex rollers for example. I've never seen a flat roller go convex but have seen flat ones go slightly concave which led to tape wander and chewing. It's also possible to wrongly diagnose as flutter when it's actually tape dropout. An amplitude error rather than frequency. They're very different with different causes.