This thread covers a potential problem that can be found in the SONY WM-DD series (exception WM-DD9) that makes the azimith unstable and even varying significantly from one cassette to another. The thread has been updated for a much simpler solution, please read post #11. NOTE1: that there is also a spring that connects the head mounting screw bracket (the one that's not adjustable) to the upper part of the carriage. If that spring is missing for whatever reason, it will cause azimuth instability. NOTE2: there are some DD units which do not have that spring (like the WM-DD33), so only consider this if a spring was fitted there from the factory. If some cassettes sound muffled, while others sound ok you should consider looking into this issue. It will be more obvious when playing Dolby encoded tapes. The problem I will be showing is a bent pinch roller bracket: this will cause the roller to put more pressure on the upper part of the tape than the lower, thus dragging the tape down. In extreme cases, this can even cause the unit to eat tapes. This eating tapes issue was presented in another thread (on a WM-2 or WM-5), which I can't find at the moment. I chose not to show the detailed procedure of how to straighten the roller bracket, as one can make it worse rather than better if not careful. You will need to take the head bridge out, as described in this thread: https://stereo2go.com/forums/threads/pinch-roller-replacement-tutorial-for-dd-series-walkman.7080/ There are 2 ways to identify this problem: - oxide residue accumulated on the roller will be a lot more visible on the upper half of the roller and a line at the middle that separates the upper/lower half - with the door removed, move the pinch roller towards the capstan with your finger. If the alignement is correct, the barrel shaped roller should touch the capstan with the middle part first.
Very good of you to put out there, this was the same problem I had with my WM-2 a little while back which I fixed by swapping the roller bracket. Also I noticed that you've roughened the capstan in the 'good alignment' JPG you attached. I've done this to only one player of mine and wondering if perhaps I should be more liberal with how many players I do it too? As in if its worth doing just for the sake of it.
@Xjmczar I wanted to put a link to your thread, as I remembered your problem, but could not find it (can't remember the title). Please add the link yourself so there is more information about the topic. I did not mention in the first post, there were 2 units which had this problem: a DDII and a DC2. On the DDII the azimuth was ok (but straigthened the bracket anyway), while on the DC2 the azimuth was off and varying from tape to tape. The funny part is the azimuth adjustment from the factory (untouched lock paint) was done such as head was tilted visibly to one side. After I resolved the issue, the correct azimuth was with the head parallel to the bridge. The 2 pictures I posted are not from the same unit (not took them on the same day), the first is from DDII, the second is from DC2. Capstan was roughened on both, as there was some uneven polish that also helped to drag the tape downwards. You can clearly be more liberal in doing the roughening, it's something that can't hurt. I usually do it when the unit is above its wow&flutter spec, but it's clearly worth doing just for the sake of it as you said. Another aspect that I should mention is the bracket should be bent in the lower part (bent inwards towards the capstan), as bending the upper part will restrict the head bridge travel to about half and the head will stay on the tape on FF/REW not giving that mechanical muting function. Will also wear the head more. EDIT: Despite my recommendation to bend the bracket on the lower part, that's not what I did in my repairs. Instead, I grinded some metal from the carriage itself (taken out of the unit), in order to make room for the roller to move further back. After repairing other DDs with same problem, my conclusion is bending the upper part is the correct repair, as otherwise there will be too little clearance between pinch roller and capstan when in stop mode (picture attached). Another interesting fact is the WM-D3 had that part of the carriage already cut from the factory, so that does not need any grinding. Also have a feeling this might be a common problem on DD units (possibly from the factory). It's the first time I see it, as discovered it by coincidence. Looking at the pinch roller, the oxide residue was much more pronounced on the top half than the bottom half with a clear line at the middle. This caught my attention: as the roller had cracks on it (talking about the DC2 with replaced roller), I thought maybe the roller has a bulge in the upper part. After replacing it, I noticed the same strange oxide residue just on the top half. Only then I realised the roller was not parallel to the capstan. To me this is something to be checked as I'm convinced these 2 units are not unique. Your WM-2 proves it actually.
It certainly looks as though it's a common problem. Interesting that we haven't really heard about this all that much before, considering our examples should indicate the abundance of this issue. I'd like to know, if this was a problem from factory, how this passed QC and managed to fly over the designers and engineers heads. Perhaps it was a delicate operation which only began to reveal itself in the form we see it today with age and use. It is rather odd though how this bracket should be manipulated in such a way to cause the problem in the first place considering it's not a very exposed component in the device. Here's the link to my thread concerning the WM2: http://stereo2go.com/forums/threads/walkman-ii-major-tape-path-problems.7399/#post-54024
It is possible that a lot of other units I serviced had this problem but I just didn't notice because it wasn't as bad as in these 2. It's something I will look for in the future and update the thread accordingly. Will also check the units I have in my personal collection (only a handful) to see if they have the problem. My theory about the issue being from the factory is the following: the roller bracket looks like it's made from a metal sheet that is stamped and bent in an industrial process. And probably after that the holes through which the roller pin comes through are drilled in a separate process. The 2 holes are not exactly the same diameter: the bottom one is a press fit for the pin, while the top is the same diameter as the pin. This could be done in several ways: - drilling a smaller hole through both parts in order to make both holes parallel to the pivot/mounting point of bracket and then enlarge the upeer one; - drilling them completely separate, which can cause misalignment problems; The offset is very slight, about 0.5mm at most so it could easily happen just by not aligning the bracket properly when drilling holes or simply by the bending process itself when the bracket is formed, as it is possible the holes are drilled before the bracket is bent into the final part. Then there is the pin on which the head bridge and roller mounts on the carriage. That may not be perfectly straight as well, although by eye it doesn't look like that's the problem. The situation with the WM-2 also doesn't suggest this being the problem, but the bracket itself. In regard to quality control, I think it would be easy to miss such a problem because in production: - the azimuth is adjusted with one specific test tape; unit is not tested after that with multiple tapes; - the worker that does the job very likely doesn't have the time to look carefully at the geometry of the head after adjustement; just obtains the desired result on the scope, then applies the lock paint and job is done; Even in further testing it would be difficult to spot a slight misalignment, especially if it does not mess up the azimuth. And of course the fact that everything is new, capstan has no wear, buries the problem even deeper. In time this will cause an uneven wear on the capstan, which will tend to drag the tape down, even with a new roller and straight bracket in the worst of cases. However, I'm afraid that many walkmans which have this problem may not present any obvious symptom.
Hi there, Just to mention that I too had flagged an azimuth stability issue - may have been in your WM-D3 calibration thread @Valentin ? - that I was able to resolve after adding a spring from the head block to door frame that I’d seen used in other D3’s - but that mine was missing. Then ran into the exact same issue when calibrating another WM-D3 recently, where again the unit was missing this spring and so azimuth would move in and out from the correct setting according to my oscilloscope. Basically, I would properly set azimuth, then I would press Stop and upon pressing play again my scope would show that azimuth was off. This second unit I actually built a tiny hook made from wire that I wrapped around the screw holding the tape head, then attached a spring in the same way that I’d seen other units use. Maybe though, instead of this being an issue of 2 units with missing springs, it’s instead related to the pinch roller brackets. Will add a few pictures tomorrow in case it’s helpful. Thanks!
I mentioned about that spring in the first post. And yes I remember you mentioning about it in the WM-D3 restoration thread. However, not all DD units have that spring from the factory (as mentioned in first post). The spring is to keep the head bridge in the same position, despite some play in the pivot point where it mounts to the head carriage. Given how small the play is in that pivot point, the spring can only make that much of a difference (it's likely the reason it is not fitted on all DD walkmans). It is of course possible that you had a combination of both problems: a bent pinch roller bracket and a missing spring. Adding that spring possibly made the other problem less severe and hence you drew the conclusion that the spring alone fixed the issue. Don't know if that's the case or not, you need to check and confirm this. Also don't know how bad your problem was... Did the walkman sound very muffled or it was only a minor azimuth error ? And please do add some pictures for reference. Take the picture so the point where the spring is hooked is visible, as the ones which don't have the spring from factory also don't have that hook below head screw.
Here are some pictures of the DIY “hook” that I attached the spring to. The wire hook beneath the screw is a piece of a much longer spring, cut and bent into the shape here. I placed it beneath the head of the screw and tightened, then used as a hook for the head block spring.
What I see is interesting: so your WM-D3 did not have that hook from the factory ? I don't see any lockpaint mark on the upper carriage hook either. The WM-D3s I serviced in the past all had this spring from what I remember, but that does not necessarily mean that all D3s had it from factory. Have seen DD models (2 that come to mind are the WM-DD and WM-DD33, but these are not the only ones) where that spring was clearly not fitted from factory (head screw lockpaint untocuhed) and they worked just fine without it. How is the alignement on your pinch roller ? I can see some different witness marks on the bottom quarter of the roller than the rest of it. That can indicate a slight misalignment.
Excellent thread @Valentin and I believe that may account for a number of people who have noted a muffled sound on playback after doing the full CG replacement on a DD Walkman. Certainly drawdown of the tape due to pressure difference along the surface of the pinch roller would be similar to azimuth setting being out of alignment.
Want to update this thread as I have more info on this problem affecting DD walkmans. 1. First of all, this issue exists on all DDs (except DD9) to varying degrees. Despite the fact in most cases it won't cause azimuth instability, it's something that should be fixed. 2. The azimuth instability problem can have other causes as well, including a capstan that does not sit straight. Note that some units have some plastic shims behind the capstan bearing/FG coil assembly. Be very careful not to lose these shims or change their position as the capstan will sit inclined to one side creating a tendency to pull the tape up or down, messing up the azimuth. 3. Have found that the real root cause of this problem is, in fact, not a bent pinch roller bracket but the pin on which the entire head/pinch roller assy slides is not sitting straight on the carriage. Noticed this because I saw uneven wear on the head on many of these units, having a lot more wear on the top side than in the bottom. While the fact head is not sitting straight isn't as obvious, as there is no reference to compare its position to, in fact it's the entire assy which sits like that. 4. Given what is stated at 3., the solution of fixing both problems is actually much much simpler than what I presented in this thread. The shaft on which the head/roller assy slides must be bent a little bit using a pair of pliers (covered in tape). I already tested this solution on a DD with lapped head and I can see after head break-in that the tape/head contact patch is now uniform, confirming the fact the head sits parallel to the tape now. Will edit the first post to mention this, as this is something that takes way less time and can be done by anyone.
