Fluctuations in tape speed - what would be the issue?

[rekloos]

I have a Otari MX5050 and i'm having too much fluctuations in speed,
i know this because i've recorded a drumstem then dumped back into logic and
it was all over the place.

Granted this machine hasn't had a 'real' tune up in a while, what would you guys think of being the issue at hand ? belts? motor?

I'm also noticing problems with the pitch control swithc, when it's on it doesn't give me the right control over pitch - again, it seems to fluctuate a lot and it's never the same, it's quite random...

thx in advance.

[Jules]

Try recording an A 440 hz tone.

(at say minus 10 or 15 on the machines meters)

Always a good idea anyway. For session master tuning calibration.

See how that behaves.

See if playback, picked up by a tuner fluctuates wildly.

Problem could be electronic or mechanical or both.

[ripple_fx1]

Hi Rekloos - I would imagine your pitch control will operate properly once you've the speed problem worked out. Your capstan motor is the most likely culprit, or more precisely, the circuit that governs it's speed. I'm speaking generally here, because I'm not familiar with the motor control of the 5050, but there is most likely a feedback loop incorporating an optical or other tach method which keeps the motor speed tightly controlled. Look for dust or other debris in the tach, or dirty connections somewhere in this circuit - and don't discount a dirty or faulty pitch control switch, as it's probably part of the PLL. Cheers! JR

[guylento]

How clean are the heads? How new is the tape? Lots of tape has shedding problems and I've seen machines actually slow to a stop because of sticky shed on the heads. No servo system can correct that much friction.

[rekloos]

@jules

k, i can do that tonite see what happens. and when you say 'playback picked up by a tuner', do you mean just play back the recorded audio and use a [guitar?] tuner to check for fluctuations?

@ripple

yeah, i figured the pitch issue is somewhat related to the speed fluctuation i'm
experiencing. i'm gonna try to open it up in the next couple of days and do some
investigating.

@guylento

the tape is brand new, Synergy 456. last i've cleaned the heads was a while back, maybe couple of months but i haven't really used this machine that much,
i mostly use it for dumping samples to it which are short but now i want to do full tracks - i will do a full clean up soon see if that helps.
also, i did notice that even when i first turn on the machine it takes a few minutes to start working properly - if i put the tape on and start playing or recording as soon as turn it on it goes very slow, i have to wait a min or so to get the right speed <<-- what do you think about that?


and thx for the responses guys

[Mr_David]

Do you mean you've got a multitrack in Logic.
You then bus the drums out of Logic - record on to tape.
Then playback the tape and record back to Logic.
Then the drums are out of time with the rest of the multitrack?

What are you doing sync wise?

Without something like a couple of Lynxs keeping your tape motor steady and everything in sync, then this is what happens.

Apologies if I have misunderstood your situation

[Phil Cibley]

Inside the capstan motor is a sensor that looks something like a tape head.
These sometimes get dirty and cause speed problems. Also clean the pot/switch
combination that controls varispeed on the front panel.

[rekloos]

How do you take the capstan out? Or how can i open it and clean that sensor?

Originally Posted by Phil Cibley

Inside the capstan motor is a sensor that looks something like a tape head.
These sometimes get dirty and cause speed problems. Also clean the pot/switch
combination that controls varispeed on the front panel.

[Bill@AudioVision]

The 5050 was a pretty basic machine, not much in the way of tension servos. Check the capstan for excessive polish. If the deck is high millage, a polished capstan can allow tape slip. The pinch roller needs to be clean as well.

[rekloos]

Originally Posted by Bill@AudioVision

The 5050 was a pretty basic machine, not much in the way of tension servos. Check the capstan for excessive polish. If the deck is high millage, a polished capstan can allow tape slip. The pinch roller needs to be clean as well.

got the pinch roller cleaned up along with the whole front end - heads, buttons, switches, etc.

can't seem to find a way to get inside the capstan or get it out, there's a flat plastic ring around the capstan shaft which keeps it from coming out when i pull on the [uscrewed] capstan motor. do i have to take the whole front end to do it?

[brianroth]

The 5050 capstan motors require oil on the upper bearings. Remove the pinch roller (keep track of any "spacing" washers that may be installed above or below the roller's center!). Unscrew the round ring that surrounds the capstan shaft itself. Beneath you will see a sort of "foam rubber" ring, and here is where you apply a FEW drops of oil on a semi-regular basis.

From the Ampex/Recordist website:

"Many Ampex manuals specify Gulf OC-11 oil, or turbine oil, for lubricating capstan and motor bearings. This oil is available from Ace Hardware. They sometimes call it "zoom spout oil." The Ace Hardware SKU is 12054; the UPC is 650760236548 (012054)."

I haven't checked recently with my local Westlake/Ace to verify, but they DID stock that at one time, and it seems fine to use with Otari machines based on my experience.

Bri

[Phil Cibley]

Originally Posted by rekloos

How do you take the capstan out? Or how can i open it and clean that sensor?

DISCLAIMER: This is not a job for the squeamish or inexperienced.
After removing the pinch roller, remove the collar around the capstan, it should
unscrew. After that, remove the back cover and remove 6 screws that hold the
circuit board upright. Once the board is flipped down, you will see the motor which
is held in place by 4 screws. The servo board is held in place by another 2 screws.
The motor and servo board should be removed as one. From there, you should be
able to see where the top panel of the motor is screwed down. All the stuff you'
have to access is under that top panel. At this point, it is VERY EASY to totally
ruin the motor. I would leave this to a pro, especially since these motors are probably going to cost you north of $1K to replace, if you can find one.
When I used to need this sort of work, I sent the motor to MDI Precision
Motor Works in Hudson, MA. (508)562-4420. The number and address may not
apply any more since the last time I needed to do this was over 10 years ago.
Good luck.

[David Kulka]

Many possibilities:

Incorrect pinch roller pressure.
Capstan motor.
Capstan servo circuit.
Incorrect supply or take up reel tension.
Brakes rubbing.
Sticky tape.

I would get hold of a owner's manual and go through the transport adjustment steps...good chance this will reveal the problem. In my opinion, most likely issue is pinch roller pressure. Try to determine whether the tape is slipping against the capstan. Does the machine tend to run slow when the supply reel is nearly empty?

[stellar]

my 5050 8 track has a switch inside to take an outside voltage speed control...if this is set to the wrong position the speed will fluctuate as described. It should be set to INT not EXT.

[rekloos]

thx guys, i got a hold of some documents with more info and things are
looking better now. i''ll probably stay away from the motor for now until i think it's necesary but i do want to oil the capstan and now i now how [it is in the manual].
found this post on 'tape project forum' where somebody said they've used
light synthetic motor oil and it's no problem - what do you guys think?

[Radardoug]

I notice you say you have not cleaned the machine in a month. Cleaning of tape recorders is VERY important!
The rule is, clean and demag every 8 hours of tape operation, or more often if the machine shows signs of shedding or gets dirty. A tape recorder is not like your DAW, it needs regular cleaning. When I receive tape recorders to fix, invariably the first thing I have to do is clean them, and then educate the owners.
I can hear you saying what's demagging? Tape recorders need to have residual magnetism removed from the tape path. This requires a demagger, usually a transformer-like device with a steel pole sticking out of it. This is turned on and moved slowly past the heads and all steel guides and then slowly away from the machine to a distance of a metre or so before being switched off. If you are serious about using your tape machine you need as a minimum a demagger and an alignment tape.

[rekloos]

hey radardoug.....
yeah, i haven't cleaned it much but i also do not use it much, i've been mainly
using it for dumping samples/sounds for saturation purposes and we're talking about running the tape for 5-10 min at at time, maybe once a week so i don't feel like i should be cleaning it as often as some ppl would, when you use it on a regular basis for full trax recordings.
that been said, i am planning to use it more often and do full trax so that's why i'm doing this major clean/lube.
i wasn't aware of a lot of the info but once i got into it i just kept learning and applying - know what i mean? - and i feel comfortable with everything so far....

so far i've cleaned the heads, all the rollers and everything else that moves including pots, switches, knobs, and all sorts of connectors inside the machine [i've used deoxit cleaner and fader lube] really good.
i'm getting some oil today as brianroth suggested and do the capstan then once
everything is back in one piece i will demagnetize the heads as i got a demagnetizer.

[Radardoug]

Sounds good! Tape recorders need TLC.

[Steele]

OK rek

Try this
Open the machine to get to the main PC board, PB 46Q. Remove the screws to the frame so you can let the PCB filp down. There is a speed switch for H and L speed. Spray the switch with Cramolin and toggle it a few times. That should do it. Did for My 5050.

Good Luck


Greg Steele

http://www.derekstudios.com/

[rekloos]

Originally Posted by Steele

OK rek

Try this
Open the machine to get to the main PC board, PB 46Q. Remove the screws to the frame so you can let the PCB filp down. There is a speed switch for H and L speed. Spray the switch with Cramolin and toggle it a few times. That should do it. Did for My 5050.

Good Luck


Greg Steele

Derek Studios

thx, got that clean.

[rekloos]

on a unrelated note, does anybody know why there's a gray cable sticking out of the back of this machine? it doesn't have any connector, it is cut off at the end and right next to the power cord. it seems related to the power because if i look inside the machine it eventually gets connected to the same board the main power cord comes out of.