Messages

1

Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: April 01, 2011, 11:43:38 PM »

Success!!

I gave the push button part of the micro switch a good blast of Caig, and that seemed to do the trick-- it pops up and down much more readily now, and when mounted back into position, the movement of the tension arm now activates the capstan motor and transport buttons, just as it should... in other words, the 2-track is now beautifully functional!!

I wouldn't be surprised if that switch needed another shot in the future-- the switch probably sat in the depressed position for **years**, while the deck was inactive-- but it's nice to know exactly what the problem was!

Thanks again to everyone, and especially to you, Jeri, for the brainstorm.

Now to clean up this girl a little bit more...  :^)

- Kevin

(And that's a good question about the interior tape mounting for the microswitch... must have been an issue at some point, because in terms of looks, it **is** rather inelegant... certainly does hold the switch in place, though!)

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: April 01, 2011, 06:20:04 PM »

Well, the microswitch finally came out-- it was mounted to the panel with some rather stubborn tape, which finally came loose with a bit of prying...

And what looked like a raised bump on the corner is actually a small pressure switch that goes in and out of the casing...  in the tension arm's "resting" position, the interior armature depresses that small pressure switch.  When the tension arm is moved into the "play" position, the interior armature is lifted off the pressure switch, which should allow the switch to pop right back up out of the casing.

Mine was sluggish, and even stuck a bit in the depressed position, as I clicked it up and down.

Time for some Caig, to see if we can make it work a little more readily..!

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: April 01, 2011, 05:53:47 PM »

That's the problem-- the switch contacts appear to be inside of a sealed unit.  When the tension arm is in the "resting" position, there's a small swinging armature inside the tape machine that makes contact with a corner of the microswitch case.  I'm guessing this causes the internal switch contacts inside to be pushed into an OFF position, which causes the circuit to the tape transport buttons to be defeated.  (That's why I now tend to think of this switch as a "kill" switch...)

When the tension arm is swung into "PLAY" position, that interior armature comes off the corner of the microswitch case, and the contacts inside are then free to move in the opposite direction, which activates the circuit to the tape transport buttons.  Now, in a new (or at least better-functioning) microswitch, the contacts move in and out of position quite readily... but on my machine, it appears that the interior of the switch has either become dirty inside, or otherwise degraded to the point that the contacts take a L-O-O-O-NG time to internally move in and out of position, once the arm is moved.

So unfortunately, as far as I can see, there is no real "button", per se-- only a raised bump that is the contact point on the case of the microswitch, and no other openings that I can see while it's mounted in place.  That's why I was hoping to be able to remove it, to give the entire case a closer look.

So if anyone has actually removed or replaced this switch on one of their machines, I'd love to hear about the process...

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 31, 2011, 11:33:49 PM »

IB:

A good suggestion, and thanks very much-- but after reading up on the issue, it appears the main symptom of such a problem is a failure of the idler wheel to fully engage or disengage the capstan, leading to speed fluctuations or other difficulties.  I actually don't have any problems in that area right now-- when the machine is operative, the capstan and the wheel interact just fine, with crisp engagement and disengagement when the transport buttons are pushed, and no speed or pitch fluctuations during playback.

Overall, I think Jeri really hit the nail on the head-- though I confess I'm still trying to figure out how to remove and (possibly repair) that microswitch.  I've taken out all three of the visible screws that were holding it in place, and the thing just won't budge from its mounting!  And from the side angle I have to use, I can't see any way to get any Caig inside of it...

Thanks again for your thoughtful idea, though...!

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 31, 2011, 01:44:45 AM »

Jeri's diagnosis appears to be exactly right... a sluggish micro switch.   With some patience, and an ear right next to the switch position, I sat next to the machine and waited while I ran an experiment... and heard the switch click after the tension arm had been raised for about 10 minutes.  The switch apparently disengages much more quickly, since after the arm is lowered, I can hear the relay click back out of position after only about a minute and a half (after which you get to wait for 10 more minutes until it engages again when you re-raise the tension arm).  So my earlier report of 25 minutes each way was more than a bit inaccurate, but you get the idea...

And apparently, the indentations in the top of the mounted switch are **not** holes in the casing, since I don't see any evidence that any Caig is actually penetrating into the switch.  I've taken off the side panel and removed the three screws that are supposed to be all that holds the microswitch in place (at least according to the exploded diagram that I finally found), but it doesn't seem to want to be removed for closer inspection.  Anyone know if those micro switches are soldered in place?  And for that matter, where a replacement might be found?

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 30, 2011, 08:30:05 PM »

**Very** well-reasoned and logical, Jeri...!!   I've now hit that switch with some Caig (as best I could... there are what look like just a couple of small openings on top of it, and it's mounted pretty close to the capstan motor); while it's drying, I'll alternate leaving the take-up tension arm in and out of out of "play" position for 20 minutes at a time over the next couple of hours-- that should give the internal switch in the microswitch an opportunity to move back and forth a bit.

And now I tend to think of that microswitch as a "kill" switch, rather than an activation switch... makes more sense to me that way.

Thanks for everyone's help-- I think we're definitely on the right track with this...!

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 28, 2011, 11:19:17 PM »

The right hand tension arm is connected to a switch, to prevent the transport from operating if there's no tape loaded, or loaded improperly.  This is to prevent tape spills, and save wear and tear on the deck.  Try turning the deck on without any tape, and then manually pull up on the right hand (take up side) tension arm.  The capstan should start turning (a handy trick for cleaning the capstan), and you should be able to get the reel motors to begin turning by pressing the transport buttons.  Release the tension arm, and these should all stop.

If that's the way your deck behaves, you have normal function.

Well, as I suspected, that appears to be the problem... my **other** (4-track) Otari works exactly that way... but this 2-track doesn't.  I went over and took the tape off the machine-- it started right up with the capstan turning and every button functional (until the stored charge dies off, at least).  This includes the transport buttons, since the motors engaged and the reels spun when the PLAY/FF/REW buttons were pushed-- even with no tape on the machine!

As for the right tension arm of this 2-track, for whatever reason, there is no "bump" or click or any feeling (or sound) of a relay engaging when the arm is moved into the play position.  The machine is fully functional, even when the tension arm is in what should be its "OFF" position.  Moving it in or out of position has no effect on anything.

And sure enough, after turning the machine back off for about 25 minutes with the reel off, the stored charge has dissipated.  When turned back on, the motors do not engage, and the capstan does not spin.  This initially looks like normal operational behavior, but as before, moving the right tension arm has no effect.  The machine only (partially) functions in the EDIT mode.

I'm guessing that this means that the switch or relay connected to the right tension arm is not functioning, or has been removed or bypassed, for whatever reason.  There's obviously still some sort of circuit contact there, since keeping the tension arm in the "ON" position (by leaving a tape threaded on the machine when it's powered off) makes a difference, by allowing enough charge to pass that the machine will start up when powered on... which at least allows it to be fully functional, if in a somewhat roundabout and atypical manner.

So I'm curious as to what to do about that tension arm switch or relay.  Historically, were they routinely bypassed, is it is more likely that this one is just dirty or worn out?  Any repair ideas?

I feel like we're most of the way there-- if this problem can be licked, then the machine will truly be able to function properly.

Thanks to everyone for all the help so far, by the way...!

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 20, 2011, 03:38:22 PM »

Anybody have any ideas on this one?  I suspect the problem is electronic...

If I have a tape threaded up on the machine, and leave it plugged in for a while (but switched OFF), I can then start the machine up and it will be fully functional  (i.e. - capstan starts turning when the machine is switched on, the HIGH/LOW speed switch works, all PLAY/REW/FF functions are fine, etc.).

But, if I **don't** leave a tape threaded up on the machine, and then attempt to start it up,  the capstan doesn't spin, and the machine reverts back to the "...will only [partially] function when in EDIT mode" behavior that I wrote about in my first post.  If I attempt to thread a tape up and play it while the machine is in this state, nothing happens.

I can however, leave the tape threaded up on the machine, turn off the machine and come back a little later (approx. 1/2 hour), and the machine is fully functional again.

It sounds as though having the tape on the machine allows some crucial relay or electronic part to fall into place, which in turn charges something in the transport functions.  Once the reel is taken off the machine, that circuit disengages, and whatever was charged (some caps, perhaps?) dissipates the necessary stored charge over a relatively short period of time.

Any ideas?  Does this sound like a reasonable interpretation?

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 17, 2011, 11:48:15 PM »

I have to admit, I think the Caig DeOxit is probably what did the trick for me-- I had concentrated on all three of the speed switches that you mentioned with regular contact cleaner (and yes, after reading up a bit more, I now know that you shouldn't use contact cleaner on a switch!), and that seemed to help; but after hitting all of them again with the Caig & some Faderlube, the machine appears to be working **much** more consistently.  Indeed (dare I say it), it appears to be fully and regularly functional again!

I think the thing that threw me the most about this BII was that I kept expecting the right tape guide (the one under the take up reel) to trip a relay when it was moved into position-- it doesn't, but that's what my 4-track Otari does, so I suppose I thought that all Otari models had that same behavior.

I'll oil the capstan soon, and there do appear to be a few capacitors in the amplifier area that could stand replacing (mostly the ones that look like tan-colored Chiclets), but overall, this machine appears to be in pretty good shape for its age.  Overall, they truly are built like tanks-- and even in stock form, they sound pretty good, too!!

- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 12, 2011, 09:31:06 PM »

It's nothing short of miraculous--

I owe a **big** thanks to everyone who helped... after setting the reel tables, blowing off the crud, some copious use of contact cleaner and the sacrifice of a large number of long-handled cotton swabs, the patient is off the operating table, and apparently now fully functional... at least intermittently.

The Otari 2-track is officially coming back to life!  :D
 
- Kevin

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Reel to Reel Tape Machines / Re: [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 10, 2011, 08:22:03 PM »

First of all, a missing part-- the polished chrome covering of the capstan is missing, and all that is currently there is the raw unpolished metal shaft-- anyone have any ideas of where to get a replacement? And for that matter, how does the outside chrome cap attach to the metal shaft? There appears to be a dimple in the top of the shaft, but it doesn't really look like a screw hole.

The matte finish shaft is the capstan, no chrome cover.

I'd say "You're kidding", but I've read enough of your writing to know that you don't joke about stuff like that, Doc...  Boy, that is one **ugly** part!  How it is able to be cleaned up for use if it oxidizes or just becomes a non-smooth surface over time?

Thanks for the hint about the controller card-- I'll try that next.

- Kevin

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Reel to Reel Tape Machines / [Troubleshooting] - Issues with an Otari MX-5050 BII-2...

« on: March 10, 2011, 02:18:14 AM »

I have an Otari that was sold as a "parts" deck... but after cleaning it up a bit and looking it over, I'd rather bring it back to life than part it out. I have the regular manual (as usual, minus the schematics), but it doesn't seem to shed much light on the issues that this deck has.

Some fixes were easy-- the reel tables needed adjusting (though there was much more available play in the take-up reel table than the supply reel table), both appear to turn freely now; the tape path has been cleaned, years of dust have been blown out of the nooks and crannies, etc... but there are still a few nagging problems:

First of all, a missing part-- the polished chrome covering of the capstan is missing, and all that is currently there is the raw unpolished metal shaft-- anyone have any ideas of where to get a replacement? And for that matter, how does the outside chrome cap attach to the metal shaft? There appears to be a dimple in the top of the shaft, but it doesn't really look like a screw hole.

One of the adjustable tape tension arms has apparently been bent at one time or another... it looks like someone tried to bend it back into shape (reasonably successfully), but I have my doubts as to how true it is... another replacement part needed.

Now the biggie-- there are some dysfunctional functions that need some solutions. The main problem seems to be that when the machine is powered up (and it **does** power up OK), the reels do not operate. None of the function panel buttons have any effect, and the capstan doesn't spin. When the tape is threaded through the path and both tension arms are engaged, the relays do not click into operation as the tension arms move back and forth. Additionally, though it may or may not be a symptom of anything, the pitch control light does not come on at all, either when the button is pulled out or pushed in.

This led me to believe that the transport system might be totally dead. However, after experimenting a bit, it turns out that when the button on the front panel of the machine is set on "HIGH" speed, and the "EDIT" button is pushed, the internal relays begin to click, the capstan motor engages and begins to spin, and the function panel buttons now appear to work... though only one tape reel motor engages, to spill tape, as the manual indicates. This **does** however, show that there are signs of life in the transport area, and that there's a chance that both reel motors actually work.

Is this one one those situations where I should open things up to see if a card is seated properly? I also seem to recall that something to do with the "HIGH/LOW" function could possibly fix this problem though I can't remember if the fix referred to the selecter button on the front of the machine, or the lever on the inside that controls the 3.75/7.5 ips or 7.5/15 ips choice.

The amplifier functions appear to work-- the VU meters light up, and the generated test tones caused movement in both in of them, which was controllable by turning the input volume knobs (as expected).

So, these are a few of the more immediate things... can anybody out there take pity on a repair newbie, and help bring this warhorse back to life...?

Thanks for any help...!

- Kevin