This is about a WM-501 (such a beauty!) that I'm repairing from what has the appearance of not having been run in decades... The azimuth is very unstable. I have replaced the pinch rollers with new ones from fixyouraudio.com, lubricated all of the parts that should be lubricated (PAO grease & watch oil), cleaned the tape path with IPA, and checked that all springs are in place where they should be, verifying with a similar model (WM-F200II) right next to it. Nothing seems to be bent, either. This is happening on several prerecorded cassettes. Azimuth can be stable in forward, and be bad or sometimes come in and out in reverse (cycle time of several seconds, very unpredictable). And then sometimes it is stable in FORWARD and bad in reverse. I am fairly certain that the high frequencies fading out is from the azimuth, because I can adjust it and the highs come right back. Anything else to try that I haven't?
Head tilt and head height can also affect this significantly. Do you adjust it by ear or use an oscilloscope and an azimuth 10 kHz tape? Adjusting azimuth by ear is prone to errors since not all the pre-recorded tapes are created equally. P.S. WM-501 is a real looker!
Doesn't appear to be head height or tilt adjustment, but I suppose I could do some creative bending to make a bit of adjustment happen. I did try grabbing the head with tweezers and manually playing with height and tilt, and can't say I could notice a better height or tilt than what it naturally has. I adjust azimuth by ear. When it's off, it's off to the extreme. However... I'm now starting to doubt how sure I am that it's azimuth. I was able to get the "poor azimuth" steady for a bit, and tried adjusting azimuth again, and the highs would come and go as a I turned the screw, but the highs would never get to what they are supposed to be. Until I changed direction and hit play and stop a few times. I'm now starting to wonder if it's electrical. Anyway, this is all hindsight, I have it back together again. There is a temporary belt in there, when the correct one comes in, I'll tear it apart again and try re-cleaning all the electrical contacts. This doesn't seem like a symptom I have ever heard from a poor contact on a leaf switch, usually it's static-y, but I'll give it a shot.
I mentioned HH and HT because they do affect azimuth. However, if you are certain nobody tinkered with the factory head setting, I would not mess with it. Period. You have to have a specialized Track Registration Tape to set play head height (adjusted for min signal). Adjusting azimuth by ear is a very challenging and not rewarding process, and it is hard to get any consistency from tape to tape. I tried to do it by ear on my SONY TC-K679 ES tape deck for years with miserable results, and it was an endless source of frustration. I would highly recommend investing in quality Azimuth Tape (eventually I did just that - problem solved!) and using PC-based scope (freeware) to get it done right. WM-501 is worth it, and you can also use it for any tape players/decks, etc. With the scope, you will see better if this is an electronic or a mechanical issue. A good rule of thumb is to perform all the transport maintenance before going into electrical adjustments. The Tapeheads forum has a ton of information on this. Good luck!
I'm going to try to find a bundle of cassettes with dolby, azimuth, etc. All I have right now is a 3KHz tape for W&F, which has been very useful. I'm starting to get to that next level from just making walkmans "work" to making them sound good, and I should have all of the proper tools. Thanks!
You are welcome! Since you are into this stuff, you will never regret having all the right tools for the job. This is the set I've got and I hope it serves you as a starting point for your search: https://www.ebay.com/itm/176013927759?hash=item28fb3f654f:g:UvgAAOSweWdhHmG6 The quality of the tapes is excellent and it is an unbeatable value for the money.
I would check the alignment of the capstans relative to the cassette shell: remove the door, put a cassette in and observe if capstan sits perfectly in the middle of the hole. Additonally, check the alignment of the pinch rollers relative to the capstan: when you look from the side, is the roller parallel to the capstan ? When you slowly push it towards the capstan is the middle part touching first ? To me this looks like a a problem of tape curling at the pinch roller (which will mess up the azimuth), not an adjustment issue. It's a problem I've seen before on walkmans from these series, some having the pins on which the pinch roller bracket slides on not perfectly straight. In general, walkmans that use these small pinch rollers are very sensitive to capstan/pinch roller misalignments. Is the head height even adjustable on the WM-501 ? The service manual doesn't mention anything about such adjustment. Also, there are no shims between the head and head bridge to suggest there was such an adjustment done at the factory. While I agree that for a perfect adjustment a test tape is needed, one is able to adjust by ear and get a result that's pretty close and adjust with tape later on. The fact that azimuth is varying from one tape to another has nothing to do with the adjustment itself, more likely it's a problem of tape curling at the pinch roller. And this is what needs to be solved first, before doing any adjustment. Can't really see how making the adjustment by ear will make it vary with tape, but adjusting with scope and test tape will not render this result. Azimuth instability and azimuth misalignment are 2 different problems and I think there's a confusion between the two.
@Valentin I completely agree with you about the differences between Azimuth misalignment and instability issues. Also, you have 1000 times more experience than me in the Walkman domain and electronics, so I wouldn't even presume to argue about the source of the problem. I trust your judgment and expertise. Regarding adjustments by ear or using a test tape and a scope. The test tape is recorded as a single track on the open reel and not in a shell. This eliminates Azimuth mistracking right from the start. And with the scope, you can visually bring the 2 channels as close to being in phase as possible. Alternatively, The adjustment by ear is done by using a 2-track (stereo) pre-recorded tape. There is an inherent error right there. (That's why Nakamichi invented its unique "Automatic Azimuth Adjustment" feature.) So your only reference is the high-frequency "bright" sound. With the existing shell variations, it often throws you a curve ball: some tapes sound great, others are OK, or one side is perfect, and the B side is off. I have dozens of pre-recorded tapes and not all of them are 100% compatible with each other. However, they all will sound fine on well-adjusted players. I am not saying you can't get it done, but I did not have much luck adjusting my cassette tape decks in the past. (I know more about decks than the WMs). As for the WMs, I prefer not to mess with Azimuth alignment, unless, there is a problem.
Thanks for clarifying, @euroflash ! I agree indeed that using a full track tape for adjusting azimuth is to be preffered for the reasons you already mentioned. There is inherent error in using a 2-track cassette for this adjustment, but if the shell is of good quality this error can be relatively insignificant. As said, not recommending to be done by ear (unless it's temporary and will be re-adjusted later), just stating it can get one pretty close assuming the reference tape is of good quality and well recorded. It's to be noted the 2 signals should also have the maximum amplitude. If you look at page 5 of the WM-501 service manual (this is shown in all SONY manuals), the phase can be 0, 45 or 90 degrees. So adjusting just for in-phase Lissajous curve may or may not render a correct adjustment. That's because the head gaps are not perfectly aligned on the head, so there can be a phase difference even with a full-track tape. For a perfect adjustment one needs to go back and forth between normal mode and XY mode. The difference you mention between side A and side B (if you are reffering to autoreverse units) is typical to autoreverse units because there is a bit of play in the head bridge and also you have 2 different pinch rollers and one might slightly pull the tape up or down during playback, messing up the azimuth. Hence why some units (like the WM-501) have independent adjustments for FWD and REV. Yes, usually if the lock paint has not been tampered with the adjustment is good. When I service a unit, I measure its frequency response, if it doesn't have any anomalies, I leave the azimuth as-is.
@Valentin , "Yes, yes, and yes" on every comment you've made. I prefer to follow the Lissajous Curve to achieve a straight line (In Phase), whenever possible. And this is not always straightforward. There's a lot of back and forth. I also agree that using a frequency response tape is a great way to test the head alignment. @walkmandude Surprisingly, when adjusting by ear using commercial pre-recorded stereo tapes I often arrived at the "bad" results, 135 deg and even 180. See the image below. I also checked on the Height / Tilt adjustment in most walkmans and it is just as Valentin said, there is no provision for that. The head is factory set.
Thanks, guys. I really think this is not just an azimuth adjustment issue, and I'm now leaning towards an electrical issue. I'll be giving all the contacts a good cleaning the next time I have it open, and check for bad grounds. This is a very informative thread, though. I just purchased the array of test tapes from the eBay link, and I already have an o'scope. Very excited to adjust azimuth on the scope, and also use the Dolby adjustment tapes - more than half of my Walkmans are so far out of Dolby adjustment that I just don't use it.
An update, I have given it another go and it's been a lot of work, but sounds great now! I noticed that the head was cocked around 10-20 degrees - in the direction so that track 1 on the tape would be pressed further into the head than track 4. The metal "arm" that holds the head was bent. So I took it out and bent it straight. I thought from looking at it that it would be plastic, but it bends like aluminum or some type of cheap pot metal. It was actually a lot easier than I thought it would be. I bent it straight by eye, and it stopped being so far out of alignment that it was chewing tapes, but it still sounded pretty bad most of the time. I then found out that it would sound better if I pushed the door on it's hinge in a certain direction. I noticed that the assembly that the head and pinch rollers are on had about 1mm of play in the hinge. Not sure how that happened, this thing must have been dropped, there is a dent in the corner. I couldn't find anything bent to straighten back out on the hinge mechanism, so I put in some small plastic washers with a cut out so they would fit to fill in the 1mm gap, and now the hinge only has 1/4mm or so of play. It's very important for the WM-501 to have no play in the hinge, because if the hinge can shift left to right, that ends up adjusting the azimuth lever. After doing this, I could get it the azimuth dialed in the forward direction, but the reverse direction sounded very muddy. I also noticed some other oddities that I won't get in to, but I tried cleaning off the leaf switches again to fix that - and voila, it sounded great in both directions! These WM-100 based mechanisms tend to be some of the most challenging to fix, especially the ones with adjustable azimuth. I can see why they ended up going to fixed azimuth, there is just so much to go wrong the way that had it set up.
