Akai 4000D surprise.

[Roger13]

Hi.

I've mentioned elsewhere that I have suspected that the 4000D actually sounds superior to it's successor, the 4000DS.

Imagine my disappointment then, to discover that on this latest arrival the capstan is flawed. Not noticeable at the higher speed but with the sleeve removed it gets 'all of a flutter'. As far as I can tell the capstan is not bent. It looks and feels as though the spindle itself is not perfectly round, just a tiny bit eccentric (like me).

I'm tempted to work on it with some emery cloth but I don't want to finish up with the sleeve rattling about, plus I imagine the capstan is made of some pretty hard stuff.

Anyone experienced this one before?

Cheers,

Roger.

[Nickthedentist]

Originally Posted by Roger13

I imagine the capstan is made of some pretty hard stuff.

They're VERY hard, in my experience. Nothing seems to touch them. And If you try to straighten a bent one, they frequently snap.

[Roger13]

Originally Posted by Nickthedentist

They're VERY hard, in my experience. Nothing seems to touch them. And If you try to straighten a bent one, they frequently snap.

Looks like it'll need a transplant then. Does make you wonder how it got that way though.

Roger.

[ppppenguin]

I suppose if the capstan's a write off you could anneal it, straighten it and re-temper it. You would need to be a pretty good metalworker to do that - I don't think I'd get anywhere near succeeding.

[reelguy]

Have you checked the rubber PINCH wheel.
Sometimes these go hard and a bit pitted which can give this effect.
Try swapping the pinch wheels over first. Just a thought..
Regards Peter W reelguy

[TIMTAPE]

Originally Posted by Roger13

Hi.

I've mentioned elsewhere that I have suspected that the 4000D actually sounds superior to it's successor, the 4000DS.

Imagine my disappointment then, to discover that on this latest arrival the capstan is flawed. Not noticeable at the higher speed but with the sleeve removed it gets 'all of a flutter'. As far as I can tell the capstan is not bent. It looks and feels as though the spindle itself is not perfectly round, just a tiny bit eccentric (like me).

I'm tempted to work on it with some emery cloth but I don't want to finish up with the sleeve rattling about, plus I imagine the capstan is made of some pretty hard stuff.

Anyone experienced this one before?

Cheers,

Roger.

Sounds odd that the effect would be on the capstan without the sleeve but not with it. You'd expect the other way around. I had an Akai which had a plastic sleeve. The sleeve was not quite true and there was wow with it. But fine without the sleeve. I too would be checking the pinch roller and whether it is nice and pliant without being too soft. Also, without the sleeve the pinch roller has a bit less pressure onto the shaft. You might try pushing the pinch roller by its top cap harder onto the capstan.
If this helps it suggests it's a pinch roller issue. Maybe the rubber is gone or not enough pinch roller pressure.

Agree these shafts are really hard and almost impossible to bend without snapping them.
Just watch the shaft turning without any tape. Is it totally central? Watch the reflection of light as it falls on the shiny part. You should pick slight imperfections by the change of light reflections. Obviously it should be cleaned thoroughly.
Look at the pinch roller as it rides on it. Is the pinch roller riding up and down or skewing in any way? Is the capstan shaft worn where the 1/4" tape has been riding on it? Eventually a 1/4" groove is formed and that can play havoc with tape travel.
Are you sure the problem is the shaft? If it is the shaft, you'd expect the "wow" to be in time with each one revolution of the shaft. If it's not, it's probably not the shaft at fault.
With the smaller shaft diam. there is less surface area for contact with the tape and you'd expect more likelihood of slippage. I noticed you mentioned flutter, not wow. You wouldnt normally associate the speed change caused by a bent shaft with flutter. More a wow issue.
May be the back tension is too high. Maybe the tape is catching on something. If it's a 75 to 85 or so tape, it may have sticky shed problem and is jamming up.
How's that for a couple of suggestions!?

Tim

[Roger13]

Originally Posted by TIMTAPE

Sounds odd that the effect would be on the capstan without the sleeve but not with it. You'd expect the other way around. I had an Akai which had a plastic sleeve. The sleeve was not quite true and there was wow with it. But fine without the sleeve. I too would be checking the pinch roller and whether it is nice and pliant without being too soft. Also, without the sleeve the pinch roller has a bit less pressure onto the shaft. You might try pushing the pinch roller by its top cap harder onto the capstan.
If this helps it suggests it's a pinch roller issue. Maybe the rubber is gone or not enough pinch roller pressure.

Agree these shafts are really hard and almost impossible to bend without snapping them.
Just watch the shaft turning without any tape. Is it totally central? Watch the reflection of light as it falls on the shiny part. You should pick slight imperfections by the change of light reflections. Obviously it should be cleaned thoroughly.
Look at the pinch roller as it rides on it. Is the pinch roller riding up and down or skewing in any way? Is the capstan shaft worn where the 1/4" tape has been riding on it? Eventually a 1/4" groove is formed and that can play havoc with tape travel.
Are you sure the problem is the shaft? If it is the shaft, you'd expect the "wow" to be in time with each one revolution of the shaft. If it's not, it's probably not the shaft at fault.
With the smaller shaft diam. there is less surface area for contact with the tape and you'd expect more likelihood of slippage. I noticed you mentioned flutter, not wow. You wouldnt normally associate the speed change caused by a bent shaft with flutter. More a wow issue.
May be the back tension is too high. Maybe the tape is catching on something. If it's a 75 to 85 or so tape, it may have sticky shed problem and is jamming up.
How's that for a couple of suggestions!?

Tim

Hi Tim.

Wow! I'll try all the things you suggest in order and I'll get back to you in a fortnight. Seriously though, I shall try swapping the pinch wheel and see what difference that makes.

I suppose I jumped to a bit of an 'assumption' re the capstan. This is because if I hold my finger to it while it's turning I can feel a feint 'throbbing'. Sorry can't think of a better way of describing it. I'm assuming it's eccentric, rather than truly round. Cleaning it didn't help.

Thanks for the thought you obviously put into your reply.

Regards, Roger.

[Roger13]

Originally Posted by reelguy

Have you checked the rubber PINCH wheel.
Sometimes these go hard and a bit pitted which can give this effect.
Try swapping the pinch wheels over first. Just a thought..
Regards Peter W reelguy

Hi Peter.

I hadn't actually considered the pinch wheel, but it's easy enough to rule out.

Thanks,

Roger.

[Roger13]

Ok, here goes.

This is where I'm glad I have no videocam showing my red face to the world, and where I lose any trace of credibility I had hoped to gain.

I think I may have been using a duff tape.

I finally noticed it making 'creaking noises' on the take up spool, and when I transferred it to another machine it squealed like a stuck pig! A different tape on the 4000D has not produced the problem.

Aaagh! It's like replacing half the electronics without checking the mains fuse. Is it REALLY 40 years that I've been playing around with this stuff?

Apologies for wasting everyone's time, and if I ever get the chance I'll buy you all a drink!

Now there's a thought. Perhaps we should form a 'tape junkies' club, have a reunion social every year, and get thoroughly 'leathered'?

Regards,

Roger.

PS: Nice to have my faith restored in Japanese engineering though....

[Nickthedentist]

Originally Posted by TIMTAPE

Maybe the tape is catching on something. If it's a 75 to 85 or so tape, it may have sticky shed problem and is jamming up.

So Tim was right

Well done both of you

[reelguy]

SORTED!


REELGUY

Been there !

[Roger13]

The really annoying thing is - the tape records and plays very well with no sign of drop out. When it 'plays up' I rewind the tape, record again and it's OK for a while Then it'll start again later. My substitute reference tape behaves impeccably so I'm pretty sure the recorder is OK.

In the past tapes have signalled their exit to me by shedding oxide and giving poor recordings with lots of drop out. This is a new experience for me. I hate binning anything that is apparently 'working'.

Know the feeling?

Cheers,

Roger.

[TIMTAPE]

Roger,
Sticky shed syndrome isnt all or nothing. Some tape types were worse than others. How well the tape has been stored and how humid it is at the time also affects it. The longer the tape plays through, the more muck gets deposited on the tape heads, guides etc. You might find the sound is fine at first but by the end of the reel it's just mud sounding.
I'm baking a tape at present. It's only showing minor signs of the problem but it's a long tape and has an irreplaceable prize winning recording on it so I'm not taking any chances.
You shouldnt really even play a valuable tape with sticky shed before treatment or you will lose part of the recording forever.
To watch for trouble, play the tape and watch the tape as it peels off the supply reel. It should come off cleanly. If there's a hint of sticking to the rest of the pack, it probably needs treatment.
Back coated tapes seem to have more problems that with plain base material.
There's good articles on the net if you want to chase it up.
Regards, Tim.

[Roger13]

Originally Posted by TIMTAPE

Roger,
Sticky shed syndrome isnt all or nothing. Some tape types were worse than others. How well the tape has been stored and how humid it is at the time also affects it. The longer the tape plays through, the more muck gets deposited on the tape heads, guides etc. You might find the sound is fine at first but by the end of the reel it's just mud sounding.
I'm baking a tape at present. It's only showing minor signs of the problem but it's a long tape and has an irreplaceable prize winning recording on it so I'm not taking any chances.
You shouldnt really even play a valuable tape with sticky shed before treatment or you will lose part of the recording forever.
To watch for trouble, play the tape and watch the tape as it peels off the supply reel. It should come off cleanly. If there's a hint of sticking to the rest of the pack, it probably needs treatment.
Back coated tapes seem to have more problems that with plain base material.
There's good articles on the net if you want to chase it up.
Regards, Tim.

Hi.

Well, at least this tape is just a 'spare'. Best to just bin it and win another empty spool. Thanks for your insight.

Roger.