Messages

1

Tape Tech / Re: MX5050 problem - Thanks for having me here!

« on: December 16, 2011, 06:13:05 PM »

Hey guys, just to give you an update - the problem was definitely with the tach sensor. Referring to my earlier post, I did replace it with a coil from one of my parts machines - though it seems I didn't mount it very precisely. You know how I said the speed would fluctuate seemingly at random? Well, turns out it followed this pattern:





This appeared to be the control voltage informing the capstan motor how fast to spin. Since the source of my problem was confirmed and I was itchy to see the machine in full operation, I decided to take your advice and swap the whole motor & servo PCB assembly. Powered up and bam! Worked like a charm.


Then I went on to FULL calibration, using this original manual from Otari, starting with capstan speed. I'm proud to say that after a month and a half the machine is up and running beautifully!


I do have a few questions about reference level which I'm sure are answered elsewhere, so I'll poke around. For the record, here's a link to the lengthy thread on gearslutz which includes tech detail and a bunch of pictures, in case anyone is having the same problem. I'm so glad this is resolved!


Thanks guys,
Dan

2

Tape Tech / Re: MX5050 problem - Thanks for having me here!

« on: December 06, 2011, 08:41:14 PM »

Thanks for the reply, docb -


I certainly will try swapping the entire motor if it comes to that. I'm encouraged right now because changing out the tach sensor did result in a change in operation - even if its not fully operational. If nothing else at this point, I want to fix this damn thing because of everything I'll learn along the way!


No worries on the delayed approval. I'm glad to be aboard. And considering I have another 4 decrepit 5050s sitting in our storage closet, I'm sure I'll be contributing a lot!


Thanks,

3

Tape Tech / MX5050 problem - Thanks for having me here!

« on: December 06, 2011, 04:59:00 PM »

Hey guys, I've been waiting to be approved for this forum for a while. Thanks for having me aboard.


While I was waiting, I described at length a problem I'm facing with an Otari MX5050 B-II. The full detail w/ pictures etc can be found in this gearslutz thread. Long story short, my capstan spins too fast... about 1.4x too fast at 15 ips. So when I load up a 15ips cal tape and play the 1kHz section, the machine outputs 1.41kHz.


Speed controls (either on the front of unit or back of main PCB) have no effect. They controls DO, however, work. Changing speed settings results in the correct voltages hitting the capstan servo PCB. This led others to suspect the tach feedback coil, tucked at the bottom inside the capstan motor housing. (It looks a lot like a playback head).


So I removed that from circuit, and found that the coil was open. Or at least, there was no continuity between the two poles when using a DMM. This should test like any other coil, no? Anyway, I took the one from my parts machine, removed that from circuit, and again saw no continuity. Unsure of whether these test results meant the coils were working or broken, I installed the replacement pickup, reassembled the motor and installed it.





Unfortunately, normal operation was not restored, though playback now fluctuates in speed (with no modification to controls). One possibility: the 2nd tach pickup is also broken... Anyone have any ideas?


Thanks in advance, and I look forward to being a part of this community.

4

Tape Tech / Re: MX5050 B II 2 R/P issue(s)

« on: December 06, 2011, 04:41:09 PM »

I came across the complete calibration manual from Otari. It contains information on adjusting the bias levels on the amplifier. The pdf is too large to attach, so here's a link: otarialignmentprocedures.pdf


Hope this helps..