Hi everyone, I am working on a WM-102 where the pinch roller on the back tension side is causing the tape to ride over to the side of the roller enough to cause some tracking issues at the head. In this unit, there is a gap between the roller and the capstan but the tape still runs over pinch roller and there seems to be some level of grip causing the tape to creep past the edge of the roller. The pinch roller seems good. If the pinch roller assembly mounting post is the issue (bent or something), what is the general logic (outside of trial and error) on what nudging to possibly do here? I attached a quick sketch for clarity. I expect more back tension would help but I don't think that is an option to adjust on a WM. When autoreverse is engaged and this side is pulling the tape, it is more aligned in the middle when engaged against the capstan. Thank in advance!
simple mspaint breakdown of the parts maybe something is getting stuck and its not fully locking into the correct position, leaving one slightly engaged they ride on that ridge (highlighted), at the position closest to the roller its held back from the tape, at the end where it rounds off thats the engaged position thats what id start with checking before anything else. cant say ive heard of this issue happening before so i cant say with high certainty im pointing in the right direction here could very well be something is bent if someone was fiddling around in there before, not quite sure how theyd manage to do that though
This WM-100/200 series mechanism is a bit unique regarding the pinch roller engagement: there are 2 pins for each roller. When mechanism is engaged in PLAY, 2 of the pins (smaller ones in the back) push both rollers out at the same time regardless of FWD/REV, while one of the second pins (big ones) pull one of the rollers back depending on FWD/REV. It's to be noted the parts of the roller brackets marked in red in picture above can develop wear over time, rendering less clearance between the capstan and roller. This is why it's a good idea to grease that part of the bracket. You should be able to put at least 1 piece of paper between the capstan and roller when mechanism is in stop. There are some common problems with this carriage: 1. Roller bracket holding pins can get bent, rollers sitting at an angle relative to the capstan. This needs to be checked visually and corrected if necessary. 2. Head bridge gets bent because it's aluminium and springs (head azimuth one + retracting one) are pretty stiff. This needs to be corrected.
Thanks Squiggly and Valentin. I double checked and the pins are working properly and I have decent clearance in both stop and play positions. The tape rolls over the pinch roller and does not touch the capstan. The pinch roller, on its own, is causing the tape to ride towards the body side quite significantly. Everything looks pretty square but I will do some more experimenting. If possible, I will try to take a short video. Thanks again.
Have you checked the tilt angle of the head and rollers ? Remove the door and one of the 2 cassette holders and check visually from one side. Take the capstans plane as the reference.
sounds like worn/bad rollers then, they can skew the tape off to the side like that id check the roller surface for uneven wear, a tiny bit can be fine, but if you notice its very round or worn near the top etc id just bite the bullet and replace it/them -i would also check what valentin suggested, its possible and cant hurt to check all your bases you want the roller and capstan to be both making even, solid contact- -sorta inaccurate mspaint drawing of what i mean but you can get the general point lol slight imperfection is alright, but it sounds like yours is a bit beyond that. normally rubber will smush flat but yours either has lost material (rounded) or is severely hardened at the surface. clean with windex might improve it (make surface slightly more plyable), but id replace it in either case
Thanks Valentin and Squiggly, I appreciate your comments here. I put new rollers on and it helped but most of the issues appear to be some bending of the pinch roller assembly mounting pins. I nudged them a bit to better square off the rollers and the issue has improved considerably. I am now noting that the motor starts to slowly slow down and after 5-10 mins can drop 50-100hz. If I stop and hit play it is still slow. If I wait for a while or FF/rew, it will reset. Pretty strange. I am still trouble shooting but has anyone seen this? Happens on all tapes, motor and entire gear system has been cleaned. It’s like something heats up and starts to seize a bit. I also bypassed the battery and provided power direct to the board. Thanks in advance.
(pref with a scope, but multimeter should work) id check the motor voltage before and when it starts doing this to compare voltage- *note itll vary depending on what speed pot is set to, hence gotta measure the before first if say a electrolytic acting as a decoupling cap begins to fail itll do something like this over some extended playback time, its due to it not being able to charge fast enough to meet the motor varying voltage demand (ie it runs out eventually) you might notice it plays fine again after being left to sit for a minute, im recapping a tps-l2 with the same issue right now with known deteriorated caps. seems to be more common the older the player is its just a fact of life electrolytics fail with age eventually, ehh cant really replace the sizes found in the wm-10/wm-100 models, but valentin recommended trying smd tantalums for them if you have the tools to attempt it
Thanks Squiggly. I appreciate all the detail on this. I will do some voltage measurements and report back. I did replace the 220uf near the motor and it didn’t help. Since it didn’t fit (as you noted) I put the old one back. It only has 4 electrolytics on this so I could replace easily enough. Thanks.
