Akai GX-4000D reel table block

[evildmp]

I'm restoring an Akai GX-4000D. The reel table blocks - i.e. the entire reel table assembly, including spindle and pulley - are disassembled and appear to be incomplete.

The service manual lists a bewildering array of washers of different materials and sizes for this assembly, and worse, it's ambiguous.

Does anyone have a reel table block from a working model that they can report on, to help me work out exactly what parts are required where?

Thanks!

 

[reeltimeau]

evildmp, I'm not going to be able to help you much here as I am also having problems with this assembly; in fact, I have had a thread running here to try & solve, without success, a noise problem I'm having within this assembly. As you have found out, the manual lists many washers which seem to have to be increased or decreased depending on pressure measurements with a spring gauge. The more washers you add, the noisier the assembly becomes as more pressure is applied to the felt covered friction rollers. I don't have a spring gauge, so my attempts to get the number of washers right has been entirely unsuccessful.
I'd be interested to know what your original problem was that made you disassemble the blocks.

 

[evildmp]

evildmp, I'm not going to be able to help you much here as I am also having problems with this assembly; in fact, I have had a thread running here to try & solve, without success, a noise problem I'm having within this assembly. As you have found out, the manual lists many washers which seem to have to be increased or decreased depending on pressure measurements with a spring gauge.

It seems bizarrely complicated. Can you work out what "(A)" or "(2)" after some of the part descriptions mean?

"SUP" means it's part of the supply block assembly only.

Some parts are listed as being nylon. The washer "Flywheel Thrust (A)" isn't listed as such, but in my machine it is nylon. So what other washers might be nylon without being indicated?

The more washers you add, the noisier the assembly becomes as more pressure is applied to the felt covered friction rollers. I don't have a spring gauge, so my attempts to get the number of washers right has been entirely unsuccessful.

Maybe the felt requires renewal. But a spring gauge seems like a sensible investment. You may be misjudging the required torque significantly.

I'd be interested to know what your original problem was that made you disassemble the blocks.

I'm an inveterate fiddler.

 

[reeltimeau]

I too am an inveterate fiddler. I have a problem with the take-up reel making a noise which is obviously the felt rubbing on the adjacent roller, which it has to do to make the adjacent roller rotate. I replaced the felt, added & removed some of the washers, but the noise would only vanish if the friction was so weak as to not move the reel table at all. I'm totally baffled & am trying to get hold of a spring gauge. Basically I want someone to tell me that the take-up reel table does NOT make any noise at all on an accurately adjusted deck. I'm supposing that over the years the washers that are now in the assembly might not be exactly the same as were there when the deck was new. As to your question regarding the "(A)" & "2", well again, I'm absolutely useless.

 

[evildmp]

I too am an inveterate fiddler. I have a problem with the take-up reel making a noise which is obviously the felt rubbing on the adjacent roller, which it has to do to make the adjacent roller rotate. I replaced the felt, added & removed some of the washers, but the noise would only vanish if the friction was so weak as to not move the reel table at all. I'm totally baffled & am trying to get hold of a spring gauge. Basically I want someone to tell me that the take-up reel table does NOT make any noise at all on an accurately adjusted deck. I'm supposing that over the years the washers that are now in the assembly might not be exactly the same as were there when the deck was new.

That's correct, the take-up reel table should not make any noticeable noise.

Is it definitely the felt making the noise? Is there perhaps something impeding smooth rotation, that requires excessive friction to make it work?

 

[reeltimeau]

There is no noise when in FF, so your theory about something impeding is probably correct. The only thing I can see slowing it down is the pinch roller!! When the end of the tape passes thru the capstan, the take-up reel does spin very fast, as it does on all decks I've seen. I'm sorry, we seem to have gotten on to my problem & not solved yours!!

 

[evildmp]

There is no noise when in FF, so your theory about something impeding is probably correct. The only thing I can see slowing it down is the pinch roller!! When the end of the tape passes thru the capstan, the take-up reel does spin very fast, as it does on all decks I've seen.

Are you certain it's the felt, and not one of the other drive parts in the machine? If you remove the entire reel table, and rotate the various parts by hand you might be able to judge whether the noise is coming from the felt or somewhere else.

Try this: mount the end of the spindle in a power drill, and rotate that at various speeds, retarding the rotation of the two take-up rollers to simulate playback/fastforward conditions. Do you still hear the noise?

I'm sorry, we seem to have gotten on to my problem & not solved yours!!

Maybe someone else has a reel table they could disassemble to help identify the washers.

 

[reeltimeau]

It's definitely the felt. Put simply, it seems as if the speed of the lower roller which is being run by the motor, is greater than the speed of the take-up reel, governed by the pinch roller, therefor the felt covered roller is not pulling the other roller (by friction) at exactly the same speed, therefor the felt is rubbing & making the noise. I'm guessing that it's built this way so that when you place the deck in stop mode, the rollers slip so as not to make sudden stop & break the tape. It might be time to trash this deck I think.

 

[evildmp]

It's definitely the felt. Put simply, it seems as if the speed of the lower roller which is being run by the motor, is greater than the speed of the take-up reel, governed by the pinch roller, therefor the felt covered roller is not pulling the other roller (by friction) at exactly the same speed, therefor the felt is rubbing & making the noise.

Can you upload a recording of the noise? That might provide a clue about how it's being made. How think is your felt?

I'm guessing that it's built this way so that when you place the deck in stop mode, the rollers slip so as not to make sudden stop & break the tape. It might be time to trash this deck I think.

That seems a bit hasty.

If you can wait till I get hold of the washers I require, and reassemble mine, I'll be able to understand better what might be going wrong with yours. I doubt very much that it's an unfixable problem. These really are pretty simple mechanisms.

 

[reeltimeau]

You're right. The mechanism is quite simple and yet.............!
Why is there a combination of nylon washers & thrust washers (whatever that is) & other various washers of different materials & sizes? My deck obviously does not have the original washers.I have bought some replacements as close to original measurements as possible, but not close enough it seems. Of course the ones marked "x" which are not visible in the illustration of the block assembly, are a bit of a mystery.

 

[evildmp]

You're right. The mechanism is quite simple and yet.............!
Why is there a combination of nylon washers & thrust washers (whatever that is) & other various washers of different materials & sizes? My deck obviously does not have the original washers.I have bought some replacements as close to original measurements as possible, but not close enough it seems. Of course the ones marked "x" which are not visible in the illustration of the block assembly, are a bit of a mystery.

I think that ones marked x are either additional ones that can be added as required alongside others to increase the thickness (e.g. 4-15x and 16x, washers), or ones that belong to the take-up reel assembly (e.g. 4-13x, a spring of opposite direction).

Even this is inconsistent. You put extra washers alongside 4-14 to increase thrust, and these are (I think) 4-15x and 16x, Washer (SUP), but the ones you put in alongside the nylon washer 4-22 are called "Reel Torque Adjust Thrust". And there are other "Reel Torque Adjust Thrust" washers, but no indication in the adjustment instructions to do anything with them

I'm pretty sure now that "Washer (SUP)" refers to a kind of washer, and is nothing to do with the supply reel table, especially since their counterparts appear to be "Washer (Nylon)".

I don't understand why some parts have corresponding parts with an x for the take up reel version and some don't. For example, why is 4-21x Reel table spring plate (B) listed (i.e. the one for the take up reel) but not a Reel table pulley for that side?

They go to the trouble of listing spring plates A to C, but not D. Why?

It's all very confusing.

Daniele

 

[reeltimeau]

I've just won a set of original Spring Gauges on eBay, so I'm hoping I may be able to adjust the assemblies more accurately. Looks like that is going to be a long process; adding & removing washers until the spring gauge readings are correct.

 

[quiberon]

I'm restoring an Akai GX-4000D. The reel table blocks - i.e. the entire reel table assembly, including spindle and pulley - are disassembled and appear to be incomplete.

The service manual lists a bewildering array of washers of different materials and sizes for this assembly, and worse, it's ambiguous.

Does anyone have a reel table block from a working model that they can report on, to help me work out exactly what parts are required where?

Thanks!

Hi,

I have an Akai GX-4000D and also the service manual. If you have not got the Akai "General Operating Principles and Adjustments" for Akai Tape Recorders and Tuner Amplifiers, I would advise getting a copy. I got along with the service manual from Rick at Stereo Manuals, there is a more detailed diagram of the reel table block and adjustment instructions. (see attached pic).

I would think that "Sup" in the parts list means "Supplementary", seems to make sense as you are possibly adding more washers to increase the various tensions.