Otari MKIII Head spot Question and a few beginner questions

JoeisREELcool

New member
This is my first post so I am sorry if this is the wrong spot or if I am doing anything out of order. Please Correct me if need be.

I just got an otari mx 5050 MkIII-2 that spent most of its life in a radio broadcast studio and the rest dormant in the house of an employee. All the guides and parts move very fluidly and the machine seems to still be good for the most part mechanically besides these few things.

1. There is a completely black head marked ER above it (I presume that means it's the erase head) located all the way to the left. I'm thinking it's probably not stock but I don't really know much about this stuff yet. Anyways, the head has a dull mark on it that doesn't seem to be coming off. I'm thinking it may be really old tape residue but I don't know for sure.
So is there a more thorough way to clean than q-tips and alcohol or is this normal (or some random bad sign)?

2. The guides are super worn and I need to get at the stationary ones in/ by the heads but i'm not sure if they unscrew or if they are press fit. They look like 3 pieces. Like two larger diameter sandwiching a smaller diameter guide in the middle. Do they screw out, heat them and pull, just pull without heat, or what?

The Picture makes the black head look a bit worse than it is but the spot is on the upper left section contact pieces (If you know what I mean).
 

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OK, the left-hand head is the eraser. The actual erase elements are normally black, or dark metallic, with the rest of the head surface being plastic. Usually it's white, but it looks like some of the Otari ones are black plastic.
From these pictures I can't see anything catastrophically amiss, though there is clearly a bit of wear on the audio heads.

EDIT: Here's one I found online:
Otari mx5050 mkiii - 2 erase head - Image on imgED
...though that one looks like it's a full-track erase that wipes both channels at once. The head you have is a 2-channel eraser, which can wipe left and right independently (e.g. for overdubbing) so it looks a little different.
 
Thanks for your response

Ok, that would explain why it won't clean up like the others. Maybe most of that dullness is actually wear on the plastic. I'll post a good and clear picture of the head when I get home so you can see the actual "spot" I was referring to. Any Idea on how the guides by the head come apart?
 
Thanks for your response

Ok, that would explain why it won't clean up like the others. Maybe most of that dullness is actually wear on the plastic. I'll post a good and clear picture of the head when I get home so you can see the actual "spot" I was referring to. Any Idea on how the guides by the head come apart?

Not on that deck, I'm afraid. On most decks the guide pillars unscrew, often from the top when the head cover is removed (or flipped open if yours does that). The tape lifters, that depends. On some of the cheaper TASCAM decks they're literally welded to the lifter assembly and can't really be replaced or rotated. On the Otari MX80 they're screwed in from the bottom, but the 5050 is probably quite different.
 
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I got some pictures of the head up close. The white part is more of a magnified reflection than anything else. But what the pictures do pick up is the weird speckled almost rust like pattern on the head. That's more of what I was seeing. It's just a little worse on the top so it looks like one spot in person. Is this normal or am I over exaggerating the problem?
 
They do look a lot more textured than the erase heads I have, but I don't know the 5050 well enough to know if that's normal. Hopefully someone else here has more experience with them and can chip in.
Have you actually tried the machine?
 
Yes, the heads look fairly worn but the interesting thing is that you appear to have both half track and quarter track playback heads - I don't know how standard this was with these machines. The erase head looks clean to me although I don't know about the texture. Does it play tapes properly?
 
Yes, the heads look fairly worn but the interesting thing is that you appear to have both half track and quarter track playback heads - I don't know how standard this was with these machines. The erase head looks clean to me although I don't know about the texture. Does it play tapes properly?

Standard option from factory. I think Miroslav mentioned recently that he got a Otari 1/2 track that had 1/4 track playback option, it can come in handy.
 
Yes, the heads look fairly worn but the interesting thing is that you appear to have both half track and quarter track playback heads - I don't know how standard this was with these machines. The erase head looks clean to me although I don't know about the texture. Does it play tapes properly?

Unfortunately I don't have any tape to play with it yet. I should be able to get a 7 inch spool of RMG/EMTEC 911 mastering tape in a couple days from amazon by Saturday or Friday but nothing untill then. I don't really plan on playing many (or any) pre-recorded things.

'
 
The goal is to get the guides (at least the really badly worn ones) turned to a good spot before the tape gets here. The guide right before the erase head is worn a lot more at the top than the bottom which is what really made me want to get the guides rotated before playing tape on it... not that one tape would matter that much. I figure now is a good time to do it while I'm fired up about having the machine and no tape to play.

I gather from common consensus thus far that the erase head "is what it is" and I need some testing to see what it really does. So I'll do just that when I get the tape in a few days.
 
If the guides aren't evenly worn from top to bottom then it is worth checking the whole tape path to see if anything is bent. Bent tension arms are often a cause of this sort of problem.
 
If the guides aren't evenly worn from top to bottom then it is worth checking the whole tape path to see if anything is bent. Bent tension arms are often a cause of this sort of problem.

Ok, the one before the erase head was the only one with serious uneven wear in my opinion. The one before the capstan looked a little but I'd think the arms wouldn't affect the wear since the capstan is in fact right after that guide and the first thing before the erase is the roller that generates the time for the counter. Is there a standard method for checking the guide arms? I dont thing it'd be easy to put an indicator on.

Also all the guides have been rotated now. The methods and work required took a bit so I'm thinking of posting a how to when I get a chance to set down and put up all the pictures and stuff.

The wear I was talking about should be clear in the earlier pictures I posted. You may have to zoom in a bit though.
If you need I can blow up the part with the guide and repost it. Just let me know��
 
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So as an update, with the wear problem aside, the tape is on and after properly setting up 1 JBL monitoring speaker (no sterio yet) the playback seems really close to what you hear when you monitor just the source. So, pretty good.
The problem is, wouldn't be right without a problem or two, the time isn't tracking properly. It tracks in reverse sometimes.

But that's just an update. I was able to get it to tack properly by moving the counter wheel up and down (it seems designed to move this way a small bit) then doing a take. And after being inside it for a while getting to the guides I dont have much doubt I'll figure out the problem quite quickly as I do this kind of stuff all the time.

Thanks for your guys' advice thus far!:thumbs up:
 
Also I've been uploading pictures using the icon in the message box thing but I haven't seen them upload since the first post is there a trick?
 
Another quick update

The time tracking is back to normal. There is a cog shaped wheel that spins the cog like parts past a sensor that together creates the time for the tape(I can post a picture later if I figure out how). So, I unscrewed the sensor part and moved it out from the wheel so I could clean the contacts on the sensor with alcahol and q-tips with most of the cotton material removed for clearance.
Now the time is almost dead accurate and I can fast forward through half of the tape and end up almost exactly where I left off (I tested it). So all seems to be working.

The only thing left is the tape path checks and there seems to be two wires hanging from the back of the meter part of the unit. They are fed through the same small spot where the nab eq switch is, not sure why. My closest guess would be for a direct head out, but why would they do it from that spot and why would a radio studio need that kind of thing?
 
If the guides aren't evenly worn from top to bottom then it is worth checking the whole tape path to see if anything is bent. Bent tension arms are often a cause of this sort of problem.

You were spot on. After just visually inspecting the arms, I found the one before the heads was quite bent. So I carefully straightened it while comparing both sides to a steel ruler. After putting the guide arm back on the machine I noticed the tape was right in the center of the guide as opposed to rubbing one side.
So thanks! I would've probably never noticed otherwise.
 
Ok, so at this point everything is working near perfectly on track 2 and I just got done opening the top section with the gauges for cleaning the electronics and lubricating the pots with fader lube f100(from deoxit). The board look great with pretty much zero dust at all basically in new condition. And the wires I mentioned earlier were found soldered to the same pin(but separate wires) of the two output xlr connectors. So probably a ground or something. Definately not something to worry about since it wont affect any circuits.

I was feeling so good I decided to actually read up some tape calibration procedures in the user manual so I can tune my setup a bit more which proved that channel two can be calibrated to work but channel one can't. :mad:

To be sure the test tone was getting to the tape through the test tones built in I plugged in my old "function generator." I played some test tones by running some wires from the BNC to the xlr input. What I found was that at 100hz the signal has the most output 1khz is less and 10 khz is about a total of 10 db under 100 hz and out of adjustment to fix by eq. It is also worth mentioning that channel one needed a bit of eq at 10 khz to get to zero at 15 ips. But the response is relatively even across the board.

I have only done adjustments as stated in the user manual. No head adjustments or internal circuit board stuff yet. I don't have an oscilloscope yet so I don't want to fool with the head until I get the right stuff (probably an MRL calibration tape included). I'll look at some of the electronics related to channel one and see if anything can be cleaned or adjusted. Any idias to what this may be?

Ps: sorry if I ramble too much. I get excited about this stuff.
 
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