FROM 4 APRIL 1995

This is an FYI document about a general laundry list I use for renovating an Otari MX5050.  The information presented here may be useful so..  use it if you feel the urge.

The routine that I do - when I go into 5050 mode - is... 

I remove the head assembly and send it to JRF for inspection and lapping.  The head assembly unplugs from the deck after removing the three "+" screws that go into the tops of three deck-mounted fixed guides.  JRF Magnetics is located in northern New Jersey (USA) and is the center of the universe as far as magnetic head reconditioning or replacement is concerned.  If the heads are too thin or just plain shot they can be replaced.  The cost of relapping varies from $175 to $275 on average.  You can save money by removing the quarter track play head if you don't need it.  JRF telephone is 201-579-5773 and ask for Dennis Charney or John French.

The capstan motor with the attached servo and drive amplifier assembly goes off to MDI Precision for rework - pack it carefully.  The capstan shaft is almost always worn smooth and needs to be resurfaced.  Most of the time I opt for a ceramic sleeve that is final ground on the shaft for minimum runout.  They also can repair the servo / drive board which is not made by Otari and is not documented in any of the manuals I have seen.  I have a copy of the schematic if anyone needs it.  I use MDI Precision Motor Works in Hudson, Massachusetts for all my motor work.  MDI telephone is 508-568-1887 and talk to Jeff Gillman.  The motor rebuild cost will depend very much on what condition the motor is in to begin with.

While the heads and motor are away I replace the power supply caps with a slightly larger and better grade of Panasonic cap from Digi-Key (1-800-DIGI-KEY).  I replace the Omron record relays with Aromat DS2E-24V relays - early machines like "HD's" may require a different relay which I can't remember the details of.  If the pinch roller is not clean and resilient or is shinny or sticky I will replace it - they don't cost much anyway.  I peel off the outer layer of the machine and clean it up as I put it back together later- while the covers are off I can get to all the mechanical assemblies which may need attention.  Guides and Lifters can be replaced (or rotated carefully to present a fresh unworn surface).  I clean things up as much as possible - cosmetics really don't impact on the audio but somehow I feel the machine "feels better".  In the process of going over the machine I often find loose or missing screws or razor blades and hundreds of bits of tape or big blobs of grease pencil or bubblegum and masking tape.  Other things like VU meter lamps (Otari part #LU 2049) can be replaced at this point.  A lot of deck functions can be tested with the heads off since the fixed guides remain.  It does not hurt the machine to run it with the heads off just don't plug or unplug things with the power on.  Always unplug the power cable from the back of the machine UNLESS you NEED the machine to be ON.  It would not be shocking to know why this is.

When the heads come back I mount them on the cleaned-up deck and I check all functions using a roll of scrap tape.  I then more or less go through the book doing deck and electronic alignments. The heads rarely need more than an azimuth tweak if JRF does the optical head alignment. Sometimes the trim pots and other moving parts need to be replaced but most of the time there is nothing actually wrong with the machine once the PSU caps, record relays and meter lamps are replaced.  Maybe the breaks are stiff and these can be dealt with as need be.  Once in a while the incoming idler roller(s) need bearings or replacement.  I buy those parts from Athan in South San Francisco.  They make some very good things...  they make a whole assortment of mechanical parts for tape machines.  Athan's telephone is  415-589-5206.

Generally it takes about a total of four hours to "do" an MX5050.  

I have played around with various mods and such and there are a number of "hot rods" that can be done involving component upgrades and minor circuit changes.  The most often done thing is a gain structure change to accommodate high flux tapes like 499 and 996 - the first amplifier the play head hits has a fixed gain and overloads before the tape does.  Machines are getting old enough now that the various electrolytic caps in and around the audio path could be replaced to positive effect.


I feel analog machines are still useful.  Analog tapes will play twenty or thirty years from now - while I have my doubts that all the hundreds of digital 1/2", 8mm and 4mm cartridges we generate each week will be fully readable even five years from now.  But that is only my opinion and not some pronouncement as to the true nature of things.