I think I know the answer to this but since I could be wrong.

[jdwk]

I have an Otari MX 55n that will be going for service soon. I am running it to see what issues I detect. here is my question;

if a tape REWINDS and slows down, but will FAST FORWARD at rapid speed, thats a problem with the DECK not the TAPE. because if it were THE TAPE, it would drag and slow in EITHER direction?

when I played a little bit of the tape ( about 10 mins worth, It sounded fine, the high end didn't rapidly disappear within seconds as it had with tape that has sss, I got rid of every tape I knew had it.

when I tried to rewind it, MOST of the tape was on the supply reel, and it slowed down pretty quick, but the FF was incredibly fast and it did not slow down one bit as the take up reel filled up. I think this may point to an issue with the deck, because I think it if were the tape, it would have slowed down in either direction. it's an older scotch tape before the back coating era ( black top front large white area on bottom box half) don't think it's as old as 111, but MAYBE not new enough to be 206. it is a live recording of Dave Brubeck, that was taped by the former owner of the tape, which is why I took a chance. Box says 'all but first number" on the front. by live I think this seems not to be from an lp, but an actual concert. unfortunately he used 3.75 ips so I have to break out the 1506 to play it, because the otari can't do it at it's current setting and I don't feel like opening up the back. I need to see if a mod can be done to the otari. there are two screwed down plates on the back that look like some add on Otari offered could be mounted where those plates that cover holes where nothing is, could have a rocker switch added, so I could go easily between low speed and high speed setting on the Otari.

side question, anyone with an Otari MX 55n that has something installed where those plates on the back are? what were they for?

 

[jdwk]

here is the pic of the back, so you can see the plates I am referring to.

 

[Blue Shadow]

Expect there is an adjustment to reel motor torque for winding.

 

[DMRanney]

I find that it makes a bit of a difference when the Reel Size switches aren't set appropriately.

My MX 55 connector panel is just like yours. Wild Ass Guess: maybe those blank plates are for the all-in-one version where all the amp-to-transport connections are internal while the studio version with the transport and amp separated has sockets where those plates are? Or maybe they're for optional Remote Control, Time Code, Dolby, HDX, or god knows what else. I did see one where the plate on the far right had a socket labeled Fader.

BTW it's REALLY easy to switch the speed pairs. The back panel is designed to hinge down and stay just like an old writing desk. And once you locate the proper dip switch it's as simple as can be. You can do it in under 5 minutes.

 

[for_p1]

Expect there is an adjustment to reel motor torque for winding.

MX55 uses microprocessor controlled transport. There are not many adjustments there.

I would start with modern reel of tape like RTM911 and check how it works with it first. It does not make any sense to change speed range from 15/7.5 to 7.5/3.75. It will require full re-calibration after that change. And then re-calibration again after changing back. If playing at 3.75 speed is important, it is better to use a dedicated machine for that.