Otari MTR90 mkII Take Up Reel has the wobbles....bearing replacement?

[stuartpre]

Hi, thanks for reading.

After getting my Otari MTR90 mkII 2" 24 track machine as a 'parts machine' and then fixing it all up, I have had about 6 months of fun, using the machine about 1-2 sessions per week.

Apart from replacing all the MDA power transistors and the fans and the capstan, and mechanically and electrically lining up the machine, all has been well. Until i noticed a wobble in the Take Up reel when in fast forward or rewind..

The wobble is about 5mm at the edge of reel looking down, birds eye view.

I know pretty much nothing about these motors, but after youtubing motors and phoning a bearing supply shop i guess it could be time to replace the bearings...

I found a guy who does electric motor work who can press the bearings, on and off for me..

The question: does anyone know the part number for the bearings?

And is there any other parts i need to check/renew as part of this procedure? Brushes?

And thirdly, should I do the supply reel at the same time?

Oh and does anyone know of an 'exploded view' schematic of the motors from the MTR90 mkII?

Stu.

 

[radardoug]

5mm wobble is unlikely to be bearings. Are you talking about when you have a spool on the machine? 5mm of wobble in the motor would be all over your recordings. Find a mechanical engineer with a dial guage who can check the motor runout. The so-called precision metal tape spools are often not very precise.

 

[stuartpre]

Hi Radardoug,

I didn't think of that. Certainly i haven't noticed any sound problems in the recordings.

So i just compared the horizontal 'wobble' at edge of reel/spool, it is more pronounced on my newest tape from PYRAL SM900.

I compared it with another reel i have been using RMGI which has the wobble but to a far lesser extent, only visible on the bottom surface of reel, not on the top surface of reel...

Then I switched the PYRAL reel with tape over to the other motor and yep, the wobble follows the reel, so the motors are just fine.

These reels do seem a bit thin, now that you mention it.

What brand of reel is best? I could buy some second hand tape and pick a few 'good' reels and discard the dodgy new reels as I find them on PYRAL. That is run my new tape onto good old reels.

 

[radardoug]

The reels are all much of a muchness, the only precision bit seems to be the hubs. Ampex reels were thick sided, otherwise its a crap shoot. If you are carefull you can bend them flat. Note on an MTR90, make sure when you thread the tape that you have it tight on the reel. If the tape slips and then grabs you can bend the two arms on either side. Those motors are very powerfull.