Strange noise coming from Akai GX-400PRO

[JBryan]

I was listening to a friend's system last night and he was demo'ing his new find for me...an Akai R2R. It sounded nice and everything seemed to work well but a little later while we were listening to some records, I heard a faint motorboat-like sound ('tock-tock-tock-tock-tock...') that lasted about 15 seconds. He said he hadn't heard it before and as soon as he stopped the TT, the noise went away. A few minutes later, it came back and seemed to come and go about every 5 minutes and last about 15 seconds each time.

I'm afraid I've upset him by pointing this out and now he thinks he has to find a tech to repair his deck. I'm thinking it may just need a spot of oil or such but haven't a clue where to start. I did convince him to order a manual but I'm hopeful that someone at the TP may have had a similar experience and can offer suggestions.

My query isn't simply a gesture to help a friend in that I also have an Akai deck (GX-400D) and not only do I feel a bit responsible for his purchase but I'm also concerned that this may be in my future as well. Any help would be most appreciated. Thanks -Bryan

[docb]

Was the sound coming through the speakers or was it mechanical?

[JBryan]

The noise was definitely coming form his deck (mechanical) and we only noticed it when it was idle (playback stopped) for a few minutes. It would come and go every few minutes and didn't seem to effect operation - speed and playback was fine.

[docb]

Was the capstan still turning while the tape was stopped? If so, it might be capstan bearings making a little noise. Rotating the capstan while the machine is off might help determine if the bearings are getting noisy.

[JBryan]

Thanks Doc. I'll call him tonight and try to get a better description of the noise.

[JBryan]

The noise seems to show up after the motors have been engaged. My friend said that he ran the deck through its paces while the rest of the system was shut down and didn't hear any noise while the deck was idling but when he started playing a tape, the noise came and went intermittently at no particular intervals. After he stopped the tape, the noise occurred immediately after and off and on for a few seconds every 5 minutes or so. He didn't hear any noise during FF or RW but it did show up again immediately after the tape stopped. He described the noise as a "tock..tock..tock..tock" while the deck was idling and he mentioned that during playback, it kind of sounded like the creaking in the hull of a wooden boat or on the docks (in the movies, I'm sure). Finally, he did say that he left the deck on for several hours after and noted that the "creaking/tock-tock-tock" seemed to subside over time.

Once again, he said the noise had no obvious effect on playback or tape speed. Does the fact that the noise occurs only during and after the motors are engaged and shows up intermittently thereafter and eventually diminishes suggest that something needs to be lubricated or maybe the capstan bearings are loose? Is there a clutch or something similar in there?

I realize that its difficult to make a diagnosis from 2nd hand information but I'm not aware of any shops in the Baltimore area that he can take it to. Any suggestions would be most appreciated. Thanks! -Bryan

[docb]

Two suggestions:

Look at the rotating elements and see if you can find a part that rotates at the same pace as the tock sound

Try placing the tip of a screwdriver against various suspect parts and place the fat end of the screwdriver against your ear. When you hit the noisy part the sound will transmit through the screwdriver loud and clear

[JBryan]

Thanks again Doc - I'll pass your suggestions along. -Bryan

[zako]

Since the only thing moving after stoping transport is the Capstan moter. Could be a bearing flat spot,, or just needs a drop of oil at that motor.

[ironbut]

I'd like to make one of my typical "low tech" guesses and say that the drive belt is hard as a piece of uncooked linguine #7. The rubber belts in old tape machines go through some strange changes over the decades. Some turn to goo, but most just get progressively harder. Usually the majority of this time is in storage and with the belt wrapped around 2 pulleys, it turns into a semi hard pear shape. The idler for the capstan keep turning as long as a tape is threaded but the belt (where ever it might lead to) is un-tensioned. But because the belt is in a pear shape, the idler is slowly moving the belt, little by little, until it gets to a point where the hardened curve forces enough tension to try and turn the stationary pulley. That's when you get the tock-tock-tock( it could just be the counter belt). You should be able to get a belt kit from Vintage Electronic Supply (just one of the resources you can find in the "links sticky at the top of the General forum). You should also order a service manual.
http://www.vintage-electronics.cc/index.html

[JBryan]

One more update to his symptoms... He now says that the noise is constant during and after playback. He also said that changing the tape speed speeds up and slows down the 'motorboating' accordingly and finally, when the deck is powered down, the noise continues and slowly tapers off. What mechanism has enough inertia to continue turning without power - the fan, a belt? Could a few drops of oil or a new belt (or both) be in order? I'm at a total loss and have suggested that he start logging onto the few R2R-savvy forums like this one and ask around for a shop recommendation. You guys have been very helpful and if I ever get off my butt and start recording again, I hope to join in on the fun 'round here. Thanks again! -Bryan

[ironbut]

I'm not that familiar with the exact model you guys have. I believe that the last Akai's had direct drive motors (3) but many of the ones (lower than the 647 and 747) had an idler motor which connected to a couple of functions with belts. Selection of the function engaged the proper belt. The idler motor has a large flywheel to keep the speed constant even when one of the belts was engaged. The capstan motor on my machine has a large flywheel also and even after the deck is shut off, the capstan will continue turning for well over 30 seconds. If your friend removes the back of the machine and does what is needed to get the noise to occur, if he looks toward the flywheel (with a flashlight or desk lamp) and unplugs the machine, he may be able to see what is making the noise. It could be something as simple as a warning label that was glued to the inside top that's hanging down and barely touching the flywheel, or it could be a hardened belt. You'll only be guessing until you open her up.
BTW does the counter work?

[JBryan]

Thanks IB,

I'll pass along your diagnosis and hopefully, he'll have a service manual soon.

His counter works fine but funny you should ask, mine didn't when I first got the deck. I replaced the belt but found that the gears still weren't engaging. I sprayed a bit of Deoxit on the ends of the shaft where it met the metal housing and applied a drop of light oil (Labelle 108). The counter works fine now but I can hear it spinning away in FF (its silent in RR) so I may have to adjust or replace the belt again as I'm thinking it may be too tight.

BTW, have you ever oiled/lubed your motors or flywheels? If so, what did you use and where did you apply it? Are there obvious holes marked 'OIL HERE' or did you just put a few drops on the shafts? Thanks again -Bryan

[ironbut]

I use turbine oil that was recommended by some guys over on the Ampex page of recordist.com. You can get it at the larger Ace hardware stores (call first). It's called "Zoom Spout Oiler" and you'll know why when you get it. The bar code # is    50760 23654 and is made by Norvey,Inc. out of Santa Ana Ca.. As far as where you apply it, you'll need a service manual to know for sure and if you really want to do it right, disassembly and cleaning any hardened grease is what most bearing surfaces need after decades of non use.
As far as detective work goes, Doc's suggestion is right on the money (you'll get used to that if you hang around here long). Any rhythmic noises can be traced to some rotating part, and most rotate at a different rate (because of diameter and purpose). One thing to keep in mind, the parts for these machines are all but unobtainable, so until the source for this noise can be found and a bearing is ruled out as the culprit, I wouldn't use it and hope for the best. If the capstan bearing were to seize, you might as well toss the machine.