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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 5th Aug 2016, 7:49 am   #1
saxmaniac
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Default Akai 1700 flutter

I have a valve model 1720 which is pretty well sorted but I have a speed flutter on 3 3/4. I have run out of things to try so I'm wondering if anyone can come up with something I've overlooked. The drive belt is new, pinch wheel good, capstan clean and running true, flywheel free to turn and bearings smooth and lubricated. I've got the minimum of tape back tension and take up tension so I don't think tape "pull" is affecting things. The flutter appears to be at capstan speed and is most noticeable on piano pieces and just bad enough to be unacceptable! Any thoughts anyone?
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Old 5th Aug 2016, 8:56 am   #2
Ted Kendall
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Default Re: Akai 1700 flutter

Is the motor run capacitor OK?
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Old 5th Aug 2016, 10:55 am   #3
sp10mk11
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Default Re: Akai 1700 flutter

is the flutter there at both speeds?
so if you remove the back tension and take up tension momentarily it is still there?
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Old 5th Aug 2016, 12:17 pm   #4
saxmaniac
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Default Re: Akai 1700 flutter

I replaced the run capacitor and there's loads of torque driving the capstan and the pinch wheel meets it with plenty of pressure. I will double check on removing back tension etc. It's quite difficult on this as the tape doesn't make proper contact with the head when removing tension. I have already removed as much tension as I could get away with from both feed and take up. I think it is there at 7 1/2 but vastly reduced. Thanks for replies and I'll do a bit more investigation and get back
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Old 5th Aug 2016, 4:42 pm   #5
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Default Re: Akai 1700 flutter

A bit of futher research! I put a continuous tone about 1khz and it fluctuates at the same speed as the capstan. This is true at all speeds and both with the capstan sleeve fitted and without. I've confirmed this by looking at the waveform on the scope. I'll have to look closer at the flywheel etc but whatever is causing it is not obvious
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Old 5th Aug 2016, 5:20 pm   #6
Andrew2
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Default Re: Akai 1700 flutter

Capstan may be ever so slightly bent. I've had this a few times, but mainly on cassette machines.
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Old 5th Aug 2016, 6:14 pm   #7
saxmaniac
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Default Re: Akai 1700 flutter

I had vaguely wondered about that so I'll stick a dial gauge on it to eliminate that. It certainly looks and feels straight but it probably only needs a microscopic bit of run out to play up
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Old 5th Aug 2016, 7:40 pm   #8
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Default Re: Akai 1700 flutter

Capstan is dead straight according to dial gauge. I looked at the belt which is new but not driving as well as I had thought. It's from a generic supplier and not as beefy as the original. I've put the original back in however and the problem is still the same. I think there's enough drive to the flywheel for that not to be the cause. So still scratching head! I would be glad if someone can tell me where to get a decent quality belt. (I changed it originally just as part of a general refurbishment )
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Old 10th Aug 2016, 11:01 am   #9
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Default Re: Akai 1700 flutter

Still struggling with this one! I've bought a slightly shorter belt which is thinner and more elastic. (Not knowing where anything can be got that's same as original ) There's definitely no belt slippage and belt is not so tight as to cause problems. Triple checked capstan is running true and flywheel free to turn. Speed fluctuates in time with flywheel rotation on both speeds and with or without capstan sleeve. I'm starting to wonder if flywheel could be out of balance. Thing is that this would have been the case from new so it's hard to believe. If anyone has any thoughts I would be grateful but otherwise next step is to remove flywheel and make a jig to check balance
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Old 11th Aug 2016, 10:57 am   #10
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Default Re: Akai 1700 flutter

Is the rubber of the pinch wheel supple and clean? may be a thought to spin it in the jaws of an electric drill, and use some fine sandpaper on it? just a thought.
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Old 11th Aug 2016, 12:46 pm   #11
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Default Re: Akai 1700 flutter

Yes pinch wheel is fine and I've even swapped with one from my other Akai to be totally sure. The fluctuations are at flywheel speed and everything looks absolutely fine so it's a real mystery. I might swapfflywheels with the other machine if it comes to it although this is a 1720 and the other is a 1721l so I don't know if it's compatible
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Old 12th Aug 2016, 2:39 am   #12
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Default Re: Akai 1700 flutter

I've always thought the AKAI 1700 range had too much flutter, especially the models that had changeable capstan sleeves. The models that had a fixed capstan seem to be ok eg. 1721,1722. I have a M9 that is ok without the sleeve, but has flutter once the capstan sleeve is added.
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Old 12th Aug 2016, 5:57 am   #13
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Default Re: Akai 1700 flutter

The take up tension could be causing this problem. Too much pull,
because the take up clutch surfaces are not slipping, or the idler
that shifts to engage fast wind, is out of position, can cause forcing,
or overhauling of the pinch roller/capstan.

A test would be to play the tape, onto the table, (i.e) not to the take
up reel, and see if the pitch variations are still present.
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Old 12th Aug 2016, 7:18 am   #14
saxmaniac
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Default Re: Akai 1700 flutter

I've already backed tension both ends to the absolute minimum. Originally I did have tension causing problems but there's definitely not too much pull or drag now
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