Audio Technica AT-RMX64 4-track acting up

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notbillcosby

Member
Hey! I (very excitedly) just got an AT RMX64 off of ebay in very good cosmetic shape for very little money. I just got it today and popped a tape in, and the motor has some trouble turning the tape. No weird noises or anything, it just seems... sticky, like maybe something needs to be cleaned. If i press any transport button, it seems to start turning, but the reel(?) on the right doesn't really want to turn, or slows down and gets "sticky" very quickly, then stops automatically. if I hold in on the play button, it spins for a bit (counts up to 10ish) and then gets sticky and stops.

I'm really guessing I just need to lubricate something inside. How do I get there? I bought this machine because I heard they are very easy to service. I'm not an electrical engineer by any means, but I can get around OK with a screw driver and soldering iron. Help me get started!
 
After reading some other threads and looking a little harder, I realized that it's extremely easy to take the metal face plate off of either half of this machine. I opted to open up the transport half! Duh.

IMG_3717.jpg


So here's what she looks like under the hood... Incredibly sturdy, hardly any plastic. I'm underwhelmed with the way the transport controls flex the circuit board that they're mounted on, but that's an issue I'll think about later. Right now, we need the motor to turn the way its supposed to. I'm no cassette tech, but I'd like to be!

I figured taking out the screws I labeled 1-4 in the previous picture would maybe give me access to where I needed to be, but I didn't do it because of the way the tape door feeds through it... I figured I wouldn't actually be able to remove it.

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Thoughts? Maybe it's time to take off one of the wood sidepanels...?
 
I don't really recognise these symptoms or the deck, but the first thing I'd check is the rubber components. Usually there's some kind of belt drive or idler wheel system, and the rubber tends to decay.
 
These are "direct drive" machines... though I feel like I've read people saying things about the belts anyway. Does direct drive just mean there's one less belt?

I'm re-glueing a piece of plastic around the edge of the STOP button that had been flexing when I'd push it, hopefully that fixes some of the spongey weird feel of the stop button, and makes it press into the board a little less. The stop button is a couple inches wide, and flexes in the middle when I push it. Might find a small strip of metal or hardwood that i can glue into the back of the button to provide some more support. The two posts that push down on the little digital clicky switches on the board below it are waaaay out at the edges of the stop button.

Anyway, while waiting for the glue to dry, I got antsy and took out those 4 screws. I was able to get that plastic tray part of the tape section to swing upward with the door, exposing the cluster of technology beneath.
IMG_3718.jpg


I'm sure I'm looking at this from the wrong side. Wonder if I can take the back off of this machine to get at things a little more? I know there's someone else on this board who's used one of these before, they gushed about it in another thread!
 
Hmm, yes. Apparently it is supposed to be a 3-motor deck. That thing in the middle looks suspiciously like an idler mechanism, though - the sort you'd expect to see if it used a single motor to drive both takeup and supply spools.

As you say, the interesting bit is going to be the underneath of the cassette transport, though. If it's a purely mechanical issue, the secret is liable to be under there.
 
This is my first time taking a part a tape recorder with any intention of putting it back together. Is the transport something you can normally unscrew and lift up from the front, or will I need to be looking at the underside of the machine? Yeah, I know, I could just look myself, but I'm already this far into it! Plus I'm still waiting on that glue to dry before i can put things back together and turn it upside down.

BTW, if anyone isn't familiar with this unit (most aren't, i'm sure!), then read about how awesome it's going to be once it works!
https://homerecording.com/bbs/gener...audio-technica-rmx64-cassette-4-track-290751/

Push/pull pots on the EQs to change if they're shelves or peak/dip or high pass... Push/pulls on the Aux's to choose if they're pre or post, 6 xlr ins with phantom on all of them and 1/4" ins and outs for the inserts on every channel... Geez, my 388 doesn't have most of that! There's no tape cue which sorta bugs me... but I'm guessing once I get my workflow going it won't be a big deal, considering I still have tracks 5 and 6 on the mixer to use for new input sources.
 
Here's an exceptionally low quality video with terrible camera work, but at least you can see what it is/isn't doing. I could swear that yesterday the takeup spool would lurch forward a tiny bit when I'd hit play but almost immediately slow to a stop as quickly as it started. Now, it doesn't look like it's even trying.

 
I would look underneath the transport mechanism and look for a broken or weakened spring connected to the wheel mechanism in the middle.
It looks like it uses a solenoid to move the wheel back and forth between the transport wheels to change tape direction.

A spring might be broken and the wheel is always sitting in the rewind position.
 
Had some more time to look at things today. I took the back off:
IMG_3721.jpg

The transport is under the boards on the left side. I couldn't remove anything to get at it, so i took out the two screws in the middle of the lower board that hold the transport down from the back. I flipped the machine back over and took out the 4 screws holding down the tray in the tape section, and then the 4 screws holding the tape section down. After disconnecting two ribbon cables at the bottom, I was able to tip that whole part upwards to show the bottom, using the ribbon cables up top as a hinge:
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Here's a closeup. Keep in mind that it's both face down, and upside down.
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Here's a picture after moving 180 degrees around the transport, looking down at it from the side with the heads on it:
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Back 180 again, i've circled the takeup reel that didn't seem to be moving. Eesh, I don't know what to do next. Anyone?
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Okay, so it's almost certainly a direct-drive capstan, but the reels are single-motor and using some kind of rim-drive. The third motor is probably lifting the heads up or something.

Anyway, as Jaygee said earlier, it seems to be using an idler mechanism to switch between rewind and fast forward, and that has probably broken in some way. See your third picture (post #4) - the drive wheel is in the middle between the two spools. In that photo it is driving the left spool, and for whatever reason it is apparently not switching over to drive the right one instead.
 
After putting it all together, it worked a LITTLE better! But not a whole lot.

Without a tape in, I can get it to play and fastforward, but rewinding works for about 3 seconds and just stops, like someone hit the stop button.

With a tape in, it can play (though I haven't tried it with headphones on or anything... duh! I should do that. I was using a blank tape in a clear case so i could see what was happening below it.), FF works sometimes but slows down in an uneven, gooey way. Rewind, you can hear the wheel engaging, but it doesn't move the reel. You can see the wheel spinning against the drive shaft, which means it must be slipping where it rubs against the wheel. I think some rubber cleaner is in order as soon as I purchase it. Should I try to get a drop of lube into the motor somehow? What kind of lube? I'll try the rubber cleaner first and see if that fixes the problem. The rubber on that wheel seems fine to the touch, but it clearly isn't holding on.

If it makes any difference: The wheel kinda just hangs out, swinging freely from left to right. The direction of the drive shaft turning is what makes it snap from one side to the other, just from the friction of the wheel touching the shaft. I wanted to take the motor and wheels out so i could make sure everything was as tight as it was supposed to be in there, but when I remove all the screws that hold the motor in, it wants to pull the reels out too, and they won't come out through the holes in the tray behind the tape. Aagh. Further dismantling required...
 
You could try a silicon (dry) lube in the motor and see if that helps.
Removing the motor and worm gear might allow better access for lubrication and also test the gear mechanism to see if
anything else needs lubrication.
 
notbillcosby said:
Is there something specific I should use to clean the idler wheel, or just some mildly soapy warm water and a rinse?
Click to expand...

That should work fine. I always prefer to start with the least harsh chemical and only use solvents if a good soap washing doesn't work.
 
The takup reel is not engaged when you hit play. That's why its stopping. I watched the video and because the tape is not being taken up something senses that the takeup side isn't engaged and kicks it out of PLAY mode.

Can you turn the takeup reel table by hand? Is it free to turn?

The rubber tire on that thing that looks like an idler between the two reel tables...is it at all tacky or sticky?
 
The rubber feels pretty 'normal' to me. Not sticky, but not glossy.

There's another video that I took before post #12 but didn't share... I talk too much in it and listening to that much of my own voice makes me not want to share it with others ;) Anyway, here it is. Take a look!

 
I noticed that there's these little rubber stoppers that push on the reels, i'm assuming to help it stop on a dime. Are these supposed to both move up automatically? Only the one on the left reel seems to lift up, but even when i hold them both away from the reels during a rewind, it sitll does that annoying auto-stop thing. Thoughts?

 
Something else! So, if I hold up both stoppers, hit rewind, and keep turning the right wheel by hand, it doesn't stop rewinding! Man, I really need to take the motor out and get a closer look at it, but it's attached to both of the reel tables and I don't know how to get those off the shaft in order to get the motor taken out. Damnit.
 
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