1/4" Reel to Reel help needed!

[YooDooRight]

I've just purchased a second hand Akai 4000DS 1/4" reel to reel tape machine in pretty good shape. Only issue being that recorded sound plays back a lot duller than the original source. By duller i mean all the top end frequencies in the music are lost.

BUT... when i apply a slight amount of pressure to the spool the tape is feeding off and therefore tightening the tape against the playback heads all the clarity comes back.

Does this sound like the belt needs replacing or are the heads out of alignment? The heads themselves are very clean... somethings amiss though. Any ideas?

YDR

 

[jjones1700]

My suggestion would be to start off with a good cleaning of the entire tape transport path (ie: rollers, capstan, heads, tensioners, etc.) and see what happens.

It's just a guess, but to me it sounds like either the capstan/pinch roller is slipping or there is some SSS (sticky shed syndrome) residue on the take up side of the transport.

A good cleaning should be first thing on the "to do" list when purchasing a used piece of equipment. Then again, I'm just anal about stuff like that anyway.

I'm sure other and possibly better suggestions will follow shortly from the real experts.

 

[YooDooRight]

it's possible... i did give the heads and capstan a good clean today, one thing thats not been cleaned i guess in oooohh about 30 years is the pinch roller as i've not managed to get my hands on any rubber cleaner yet. would this be a possible cause for the 'slackness' of the tape against the heads then?

 

[jjones1700]

it's possible... i did give the heads and capstan a good clean today, one thing thats not been cleaned i guess in oooohh about 30 years is the pinch roller as i've not managed to get my hands on any rubber cleaner yet. would this be a possible cause for the 'slackness' of the tape against the heads then?

Yes and no. If the capstan / pinch roller aren't pulling the slack as they should, there wouldn't be proper tape tension on the heads. However, I would think that more and more slack from the supply reel would become noticeable and lose contact with the heads entirely.

I'm leaning more towards some dirty transport parts (remember, clean EVERYTHING the tape comes in contact with..........regardless of which side is in contact) keeping the take up reel from keeping the proper tension along with the capstan and pinch roller.

Just a guess.

Anyone??

Beuller??

 

[cjacek]

jjones1700 is right so I would do the above mentioned stuff first prior to going further. If this doesn't help then I'd look at tension adjustment. But, again, I'd do what jjones recommends first.

 

[The Ghost of FM]

... I'd look at BACK tension adjustment....

Me too.

Cheers!

 

[Tim Gillett]

Lay the machine on its back and watch the tape as it passes the heads. Watch what happens when you put more back tension on the supply spool.

Does the tape move up or down? Does the tape speed slow down appreciably?

If the heads are clean, normally I'd expect the problem to be worn heads. More back tension forces the tape better into the worn slot of the head. You might find a thinner tape than say 406 (standard) will sound better because it conforms better to the worn head.

If the machine hasnt been used for a long time there may be oxidation of the head face, which should only improve the longer you run a tape across it.

It may be also weak back tension. These Akais normally used a felt clutch on the supply spool to create the back tension and it may be in need of adjustment or clean or both. A tech would use an empty reel and a spring balance attached by a cord to check the tension.

If the pinch roller /capstan is not pulling well enough the first sign of that would be erratic speed, and change of pitch on the music. That would be more noticeable before any weakening of the tape tension. Remember, at the slower speed, you have the same effect but that doesnt require more back tension. If your capstan/pinch roller is weak, any more back tension you put on yourself will cause the tape to slow and stop before much improvement in head contact. That's why I doubt it is the capstan/pinch roller causing the poor highs, unless it's causing the tape to skew up or down. Increasing back tension does tend to straighten a skewing tape.

Tim

 

[poopchute]

Have you tried demagnatizing the tape path and heads? A poorly performed demag can give you the hi-freq loss your describing.

 

[Tim Gillett]

Yes but if it was just a magnetised tape path the high frequency problem wouldnt go away when he increased back tension! Try reading his post thoroughly.

T

 

[poopchute]

Oh Im sorry. I wont try and help anyone by offering suggestions. Im really very sory that I didnt see the rule where I shouldnt post to try and help people unless I have been deemed ready for prime time. F!O!

 

[cjacek]

Oh Im sorry. I wont try and help anyone by offering suggestions. Im really very sory that I didnt see the rule where I shouldnt post to try and help people unless I have been deemed ready for prime time. F!O!

Any and ALL suggestions are always welcome, especially when done in a genuine attempt to help the next person.

 

[poopchute]

And thats all I was trying to do.

 

[Tim Gillett]

Oh Im sorry. I wont try and help anyone by offering suggestions. Im really very sory that I didnt see the rule where I shouldnt post to try and help people unless I have been deemed ready for prime time. F!O!

So should I have stayed quiet (even though I knew you were wrong) and let you lead YDR on a wild goose chase, with him possibly going out to buy a demagnetizer when it wasnt even the issue?
In his first post YDR said that when applying a little tension to the supply reel "all the clarity comes back". Key phrase.

I'm not aware of anybody who welcomes bad and possibly expensive wrong advice. Not all advice is equal or welcome.

Why have forums at all? To share our collective ignorance?

T

 

[cjacek]

So should I have stayed quiet (even though I knew you were wrong) and let you lead YDR on a wild goose chase, with him possibly going out to buy a demagnetizer when it wasnt even the issue?
In his first post YDR said that when applying a little tension to the supply reel "all the clarity comes back". Key phrase.

I'm not aware of anybody who welcomes bad and possibly expensive wrong advice. Not all advice is equal or welcome.

Why have forums at all? To share our collective ignorance?

T

I agree with what you say but was it neccessary to rub it in his face and especially by ending with: "Try reading his post thoroughly" ? There is a way to correct someone with some respect. You've shown none.

...and yes, I welcome any and all advice and sometimes it's outright wrong and you've pointed it out. OK, great but I'm glad that people are eager to help, first and foremost.

 

[YooDooRight]

Watch what happens when you put more back tension on the supply spool.... Does the tape speed slow down appreciably?

No, the tape speed doesn't slow down, the quality of sound just gets better.

If the pinch roller /capstan is not pulling well enough the first sign of that would be erratic speed, and change of pitch on the music.

Thats true, sometimes playback does suffer from erratic speed/change of pitch that generally sounds like a warped record.

The basic history of the machine (to give you a rough idea of headwear etc). One owner from new, minimal home useage then stored in a dry loft space in all original packaging till now. Its not something thats been used in a studio everyday for 30 years so i can guess the heads are in pretty good shape? they do look shiny!

Is Back Tension something i can adjust myself?

 

[jjones1700]

The basic history of the machine (to give you a rough idea of headwear etc). One owner from new, minimal home useage then stored in a dry loft space in all original packaging till now. Its not something thats been used in a studio everyday for 30 years so i can guess the heads are in pretty good shape? they do look shiny!

Is Back Tension something i can adjust myself?

First give it a thorough cleaning. Secondly, get yourself a service manual on that machine. If you plan on tinkering with ANYTHING in regards to adjustments, alignment, etc.; you will definitely need one. My next suggestion after the thorough cleaning would be lubing the appropriate points. Even though the clean and lube MAY not be the source of the problem, it will surely take those problems out of the equation and narrow down the problem. Besides, after 30 years, I'm sure it could use a lubing on the critical parts since some of the original lubricants have either dried up or are starting to get a little gummy.

Remember though, SERVICE MANUAL. It's cool to see how these things work even if you don't dig into the innards.

 

[Tim Gillett]

No, the tape speed doesn't slow down, the quality of sound just gets better.



Thats true, sometimes playback does suffer from erratic speed/change of pitch that generally sounds like a warped record.

The basic history of the machine (to give you a rough idea of headwear etc). One owner from new, minimal home useage then stored in a dry loft space in all original packaging till now. Its not something thats been used in a studio everyday for 30 years so i can guess the heads are in pretty good shape? they do look shiny!

Is Back Tension something i can adjust myself?

Again my guess is the heads are worn, or just have some oxidation, and require more than usual back tension to get good tape contact. You could try a simple test for back tension on the left platter. With no tape, put the unit in "play" mode. Now, gently turn the left platter clockwise and then anticlockwise. Clockwise there should be very little resistance and a vibrating sound which is normal. Anticlockwise it should be harder to turn and there should be a hissing sound as the felt clutch slips.

If by merely placing more drag on the left reel you are able to get good reproduction without any hint of slowing down the tape, it's possibly just lacking in back tension.

I havent done one of these Akai's for a while but adjusting the clutch will be a bit of a fiddle. You need to remove E clips and carefully remove and make a note of washers etc and the order they go back together. You probably need to add an extra washer to pretension the clutch spring for more back tension.

If there's a deep groove in the heads the width of the tape, that may be your problem. Can you take a good photo of the heads and post it here?

Tim

 

[jjones1700]

I havent done one of these Akai's for a while but adjusting the clutch will be a bit of a fiddle.

Tim

I took one look at the boards and such in my GX-230D and said "to hell with it". I'm not up to totally tearing down a machine to make a voltage adjustment on the capstan motor. So mine plays about 2% slower than my other r2r decks.

Hopefully YDR won't have to do much mucking around on the insides, if it's anything like my 230D. Then again, the 4000 is older and is probably more "user serviceable" than mine.

 

[Tim Gillett]

I took one look at the boards and such in my GX-230D and said "to hell with it". I'm not up to totally tearing down a machine to make a voltage adjustment on the capstan motor. So mine plays about 2% slower than my other r2r decks.

Hopefully YDR won't have to do much mucking around on the insides, if it's anything like my 230D. Then again, the 4000 is older and is probably more "user serviceable" than mine.

As YDR described it, it's a mechanical problem, not a board issue.

Tim

 

[YooDooRight]

Okay folks, here they are... and in taking the pics i've maybe answered my own question ("replace the Capstan" anyone?)


My new toy...

Tapeheads 1...

Tapeheads 2...

Dirty Capstan?...

And this is where i start panicking... i noticed on two sections of the Capstan, small dents in the rubber where it appears the previous owner may have left the machine in pause for a long period of time causing the capstan shaft to indent the rubber... could this be it? And more importantly, am i screwed??...

Apologies in advance for the size of the pics.

YDR