AKAI REEL-TO-REEL 1721L problem!

[johnctb]

Hello,

I have a super Akai 1721L reel-to-reel which operates perfectly EXCEPT that the back pressure on the left-hand spool is so great that it slows down the tape transport / speed. This problem (friction) gets worse as you approach the end of the tape.

Is this something that can be sorted out? Grateful for any thoughts.

Thanks

John

[Kat Manton]

Originally Posted by johnctb

[...] back pressure on the left-hand spool is so great that it slows down the tape transport / speed.
John

I've got an AKAI 1721L too; I've just whipped the deck cover off to have a look inside as it's been a while since I was in there.

It looks like the feed spool back tension is controlled purely by means of a clutch under the reel hub; without further dismantling I'm not sure if there's any adjustment available. It seems unusual that the back tension has increased, it's usually the other way around...

One thought, as the deck is driven by a variety of idlers; if any of these are slipping the machine might not be able to pull tape off the feed spool even though back tension is correct.

If it's switched off; but put into 'play', does the feed spool feel excessively tight?

Kat

[johnctb]

Thanks for your ideas. If I switch into "play" position, the tension on the LH spool remains exactly the same as the tension when in the "off" position. However, when I switch to fast forward, the LH spool frees up beautifully. Curious!

[Kat Manton]

Originally Posted by johnctb

If I switch into "play" position, the tension on the LH spool remains exactly the same as the tension when in the "off" position. However, when I switch to fast forward, the LH spool frees up beautifully. Curious!

That seems correct; mine does the same - watching the mechanism with the cover off, in 'stop' the LH hub is braked via the clutch used for back tension in 'play'; in 'f.fwd' the brake is released.

The back tension may seem a bit high if you're used to machines with pressure pads, on this machine it's the back-tension alone keeping the tape in contact with the heads.

It might be an interesting exercise to remove the top cover then lace a tape up and watch what happens, you might spot a slipping bit of drive mechanism. I still suspect this may be the problem...

Alternatively, give the idlers and the wheels they engage a good clean and see if that helps; it's probably a good idea anyway.

Kat

[Kat Manton]

Ah! My forgettory unremembers (beer? old age? or is it the contact cleaner?) whether the capstan is driven by a belt rather than one of the idlers; either way if there's slippage then it'll struggle to keep speed up especially when the LH spool is near empty.

I'll peer inside mine again tomorrow and get back to you. If there's a belt anywhere it's not immediately under the deck cover.

Kat

[reel-to-reel-man]

Hello, is there an arm which rests on the tape, usually to control the back tension this arm is sprung loaded, then the reel gets slack, the breaks go on and visa versa, if not there could be just a spring which you can slacken off, if you have a picture of the mechanics I could help a little further as I don't have this model, but I am sure it shows come remembrance to the GX4000D

Also have a look at this

http://cgi.ebay.co.uk/AKAI-1721L-ree...QQcmdZViewItem

fatuly, it may go cheap

[Welsh Anorak]

Er.... not sure if I'm being silly here but have you checked the tapes themselves? A sticky tape can often give the impression that the back-tension is too high as can a tarnished guide!

[Kat Manton]

Originally Posted by reel-to-reel-man

Hello, is there an arm which rests on the tape, usually to control the back tension this arm is sprung loaded, then the reel gets slack, the breaks go on and visa versa

The arm you mention is after the capstan, so controls take-up tension and operates the auto-stop - a microswitch which disconnects the power to the entire deck (amps and all) if the 'automatic' slide-switch visible between the transport controls is 'on'. It doesn't operate the brakes, and is unlikely to be involved in this fault.

Originally Posted by reel-to-reel-man

if not there could be just a spring which you can slacken off,

This doesn't have the common brake-band arrangement for controlling back-tension (like the Wearite deck) - it's controlled by a friction clutch also used as the brakes in 'stop' - basically there's no difference in mechanical terms between 'stop' and 'play' as far as the LH hub is concerned. The brake comes off in 'fast-forward' and an idler drives it in 'rewind'.

I'd be very surprised if it's gone out of adjustment so far as to cause this fault; (particularly as I find these sort of clutches usually go slack, not tight - it's of the 'two plastic wheels and a disc of felt' type) - Knowing this machine, I really think the most likely cause is that the capstan torque is reduced due to drive slippage, so as the back-tension increases towards the end of the tape the drive slips and capstan slows - but the back-tension is correct and not in need of adjustment.

Reducing the back-tension might improve speed stability, but would reduce the tape/head contact pressure; (as noted there are no pressure pads) so I don't think this is the way to go until all bits of drive mechanism between motor and capstan are known to be in good order.

I remember it being difficult to slow this deck down with a finger on the feed spool flange, the drive to the capstan is pretty torquey. I suspect the tape would stretch or snap before the thing slows down - hence my suspicion as to the cause of the fault in this case...

(A good general rule is not to adjust anything until everything involved is known to be in good order - and that goes for electronics as well as mechanical stuff. Unless 'The Phantom' has been inside, anything adjustable rarely needs adjustment once the fault is found.)

Kat

[johnctb]

Many thx to Kat and others for taking the trouble to offer help. It's much appreciated. Here goes! John

[reel-to-reel-man]

Good points about the tape, usually the tell tail signs is oxide build up also a screeching sound coming from the tape, yet if this was true, the supply reel would not be tense, only the take-up reel. Keep us posted, I will be taking an AKAI apart soon and will offer any advice I have to you but its been over 2-3 years since I have looked inside one, my knowledge is a little rusty (As I am sure the parts in the AKAI will be too )

[DOFFERY]

Re. the 1710 problem, first check the pinch wheel, if too shiny ,clean slightly roughen, if this fails see if you can stop the capstan shaft easily with your fingers, if so, belt problem, these are available. Lastly a common problem with the Akai clutches is the felt disc within the clutch make up, this can be replaced but do be careful as there are many items in this clutch .

1 check pinch wheel,
2 check for slack belt(capstan shaft as above)
3 feed clutch felt

[Kat Manton]

John - See my response to another thread here for some further suggestions which may be applicable.

Regards, Kat.