MSR-16 Erase Issue

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stolenbaby

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Hi All! New to the forum, but long time reader. I just picked up an MSR-16 that I'm trying to get back into working shape, and I'm running into a problem with erasing. Basically, every even track erases, and every odd track doesn't. If I hit record and press my finger into the tape a bit past the erase head, it seems to work ok? That makes me think it's an alignment issue, but the erase head on the MSR-16 doesn't move (according to the manual). For the play/record head, I only see azimuth adjustments, which I'm afraid to mess with as I don't have a test tape or anything. I'm fairly new to this kind of thing, so if anyone knows what's going on with the machine, I'd appreciate it- thanks!
 
stolenbaby said:
Hi All! New to the forum, but long time reader. I just picked up an MSR-16 that I'm trying to get back into working shape, and I'm running into a problem with erasing. Basically, every even track erases, and every odd track doesn't. If I hit record and press my finger into the tape a bit past the erase head, it seems to work ok? That makes me think it's an alignment issue, but the erase head on the MSR-16 doesn't move (according to the manual). For the play/record head, I only see azimuth adjustments, which I'm afraid to mess with as I don't have a test tape or anything. I'm fairly new to this kind of thing, so if anyone knows what's going on with the machine, I'd appreciate it- thanks!
Click to expand...
You could be having an issue with not enough tape tension and/or just not enough pressure @ the pinch roller.
 
RRuskin said:
You could be having an issue with not enough tape tension and/or just not enough pressure @ the pinch roller.
Click to expand...
Interesting- I did replace the rubber on the pinch roller, but I'll look at the tension- I think the service manual has a section on adjusting that which doesn't need any fancy tools- thanks!
 
If you look at the erase heads in some machines the gaps can be staggered. What you describe is a case where the head gaps that are maybe first have correct head wrap and the one that are odd do not or are barely in contact. This is a tape to head contact issue. Putting a dry cotton swab to the back of the tape to aggravate the interface should only result in a decrease of performance if the head is positioned properly but when you see a increase that means the head to tape contact is not ideal and that that head needs adjustment so all track are getting a good contact. This bottom head mount system is not the ideal way and so there is a screw mounting the head from the bottom that holds the head while two hex nuts allow for adjustment and lifting the head from the rear. People on the assembly line do not always get the deck perfect and then there are a lot of years since it was built so all kinds of characters could have been at the deck up until now. The head might need to rotation to get the head in correct tangency.
 
According the the manual for the MSR-16, "the erase head is fixed and has no adjustment". There seem to be only 2 screws that hold it to the block (top and bottom), so nowhere to go with that really, plus the supply side tape guide is locked in place on the same block. I haven't had a chance to check the tension out, since it turns out you do actually need special tools (a spring scale at minimum, a tentelometer would be better). So, perhaps adjusting that like Rick said will pull up some slack on the take-up side of the erase head and fix the issue- I'll update when I get a chance to try! Here is an image of the block- the only adjustments seem to be azimuth for the play/record head:

Screen Shot 2021-12-22 at 9.24.12 AM.webp
Let me know if I'm misunderstanding!
 
The R/P head Azimuth adjustments are usually sealed with some type of Locktite type liquid. Does it look like someone has tried to adjust them?
 
The clear-ish goop on the 2 adjustment screws appears to be undisturbed, so I don't think anyone has messed with it.
 
The tensions on machines are often messed with and terribly wrong. I had a 48 that had a play tension of about 20g/cm when it is suppose to be 80. The hands that get into these do not have the right tools nor do they have a clue what they are doing and really don't even know when they mess them up. A person brought me some push on rubber parts thinking he was smart and bought these- same trap, don't buy any push on rubber parts as they never work right and I will never allow those to be put on any machine I work on. They are junk.
 
Finally got a spring scale and was able to test the pinch roller pressure via the manual, and it checked out perfectly (1.6 kg). Unfortunately, the tape tension measurements require a tentelometer, and even if I could find one for sale, it would probably be for more than what I paid for the machine, haha!
 
That is why I tell people that when they take a unit with servo tension to a shop and they do not have the right tools don't even leave it there as all they will do is goof it up.
In unit that have erase problems I check signals at head wire, then in even one case I used the scope to test the signal level at the pole piece and the one channel that was bad was drastically lower even though the input was the same and the resistance was the same. Things can still happen to old head that can make them not work whatever they are. This was a gold like two channel erase head- these are the oldest items. Like on the A4010S.
 
I finally purchased a tentelometer and adjusted the tape tensions per the manual. Unfortunately, it did not solve the problem- the odd tracks still erase poorly. It seems that the tape's path between the erase and rec/play head is out of alignment so that the erase tracks are not making good contact on one side of the head, but that it is also not adjustable on this machine (only azimuth, no height adjustments). I may go ahead and remove the entire head assembly to be sure. If anyone has more ideas, just let me know!
 
You mentioned that when you applied pressure with your finger that it erased ok across the entire tape so it isn't the head. Is there a center guide misaligned or worn guide somewhere in the path?
 
It seems to erase when I place a little bit of pressure in between the erase and rec/play head. Tricky thing is, there's nothing in between those two- no guides or anything. I did notice that the tape is running into the top flange of the guide on the supply side right before the erase head, so maybe I'm assuming the wrong side is having the issue, but I have the corresponding tension roller screwed down to its lowest point already, so I'm not sure what else I can do there for better alignment. I'll keep messing with it, but open to any ideas!
 
stolenbaby said:
It seems to erase when I place a little bit of pressure in between the erase and rec/play head. Tricky thing is, there's nothing in between those two- no guides or anything. I did notice that the tape is running into the top flange of the guide on the supply side right before the erase head, so maybe I'm assuming the wrong side is having the issue, but I have the corresponding tension roller screwed down to its lowest point already, so I'm not sure what else I can do there for better alignment. I'll keep messing with it, but open to any ideas!
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If the tape is hitting the top of the guide, that guide is too low. There has to be a way to raise it so the tape is running evenly through it.
 
So here is the tape path from the manual:

Screen Shot 2022-09-12 at 11.41.12 AM.webp

The tape guides are not adjustable, and I noticed the tape rubbing and almost curling up to the top of the left tape guide, but only when playing. I removed the cap of the left tension roller and adjusted the screw to its lowest point, but it persists. I believe the right one is also at its lowest point. Perhaps the assembly the tension roller is on was bent at some point, or my reel table height is causing issues after the tension roller? Is it possible that the pinch roller is somehow pushing it up? It seems to sit fine in the right tape guide, but there is that dummy head there. This is my actual machine:

PXL_20220910_191657051.MP.webp

PXL_20220910_191650261.webp
 
Do you have the service manual? Is there any way to move the supply guide back? Perhaps it's too far forward and not allowing proper contacted with the headstack.
 
The diagram from my previous post is from what I think is the service manual (has schematics and layouts). As far as I can tell, the guide just screws right into the stack. What do you think it means that the tape seems properly placed until it starts moving?
 
If the guides & reel table heights are properly set and the only problem is with the erase head, then I'd be looking at that head being too far back. Even if there is no adjustment per se, there could be some wear at the mounting point. Just out of curiosity, is this problem repeatable with a different reel of tape?
 
Good question! I have only one other reel of ATR master tape- I'll try that next. Thanks!
 
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