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Otari MTR-90 mkIII maintenance questions
Old 1 week ago
  #1
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Otari MTR-90 mkIII maintenance questions

I recently bought an Otari MTR-90 mkIII machine and I'm looking for some advice on maintaining it/fixing it up. It's generally in good shape but it's seen a lot of use over the years and could use some tweaking to get things just right. If anyone has some insight into the following issues I'd love to hear about it:

- The tape lifters work, but seem to move very sluggishly. It seems like the problem could be in a couple places - either the airpot used for damping the lifters' motion, or the moving parts in the lifter assembly are getting gunked up and they need to be cleaned and lubricated. Anyone has experience with this issue?

- I know bent swing arms are a common problem on these machines. If this is the case, is it pretty obvious? Mine look straight and so far the thing seems to be handling tape just fine.

- I saw Athan sells replacement bearings for the rollers and maybe the capstan motor as well. I'm curious how difficult of a job it is to replace these bearings, and how many sets of bearings are needed (are there two sets in each roller?)

- Has anyone had luck finding quieter fans for the machine?

Thanks!
Old 1 week ago
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Re the lifters, probably dirt and gunk. Clean and lubricate. Re the swing arms, it will show up in the way the tape sits across the heads. Look for same tension top and bottom of the tape. Also record 10 kHz tone, if you have a lot of wavering on some tracks its a sign of bent arms.
Generally the top tracks, because the arms bend in.
Roller bearing replacements are pretty easy. With the rubber rollers, make sure you get the set screws in the areas that are cut on the shafts. You will see what I mean when you take the rollers off.
Old 5 days ago
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Quote:
Originally Posted by Radardoug View Post
With the rubber rollers, make sure you get the set screws in the areas that are cut on the shafts. You will see what I mean when you take the rollers off.
I tried removing one of the rubber rollers and it would not budge. Can't tell if I'm missing a screw somewhere, or if it's just stuck and I need to pry it off (I didn't wanna apply too much force). I removed the screw on top and the two set screws in the side cutout. Am I missing something? In looking through the manual I didn't see instructions for removing them, although I guess the exploded view might be useful.
Old 5 days ago
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The rubber rollers are held on by the two set screws in the deep holes. If you remove them completely you should be fine. There are flats machined on the shaft that the set screws go onto to stop any shaft slippage. The roller will be very tight on the shaft. Use a bearing puller or similar to remove the roller.
Mark the top of the shaft and the roller so you can put it back at the exact same place so the screws will bite into the flats.
Old 5 days ago
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Thanks - and the questions keep on coming. I got the left side rubber roller (tach roller) off, it looks like I'd need to remove the entire tach roller assembly to replace the bearing. Is that correct or am I not seeing an easier way? Also, how necessary is it to have a specialized tool for removing these bearings? I see I'll need something special (forgetting the name) to remove the little c-shaped retaining clip, but what about the bearings themselves? (forgive the ignorance, last time i replaced bearings it was in my skateboard's wheels when I was 12)
Old 5 days ago
  #6
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Yes, its easier to take the whole assembly out. You need circlip pliers to get the circlip out. Your local auto store will have them. I probably wouldn't do a bearing replacement until I had had the transport running and knew there was a problem. You probably should change the rubber rollers, which is why I thought you were pulling them off.
Old 4 days ago
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Thanks. The rubber rollers may have already been replaced, I'm trying to figure that out from the previous owner. The bearings I probably could just leave alone, just one of those things I figured I'd replace if it was reasonably easy. What are common symptoms of bad bearings in these machines? noise? rough feel when turned by hand?
Old 4 days ago
  #8
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Its all about the tape path. Bad bearings will show up as noise in wind mode. If you can feel roughness when you turn a shaft, then they would be bad. But the first thing is to get tape on it and record. If you are serious, buy a wow and flutter meter. They are available cheap on Ebay. Then measure your machine. If the W&F is to spec, then stop worrying about it. Or record long chords from an acoustic guitar. If it sounds fine, it probably is.
I would be more worried about bent arms on an Otari.
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