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Old 1st Nov 2016, 3:42 pm   #1
monaghana
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Default AKAI 1721L run capacitor question

Hi everyone, I recently bought an AKAI 1721L and it appeared to work ok. Play, record, fast forward and rewind all fine. It was recording but sound wasn't great and old recordings were coming through on playback. Cleaning heads resolved this and sound quality was ok.
Last weekend I was trying various ways of recording from a Sony amp via DIN and phono coneections and it started to play up on rewind, stopping almost immediately. Fast forward still ok but when I tried to rewind it would halt. I'm pretty sure the capstan also stopped. I tried a few things and it then started to fail on play. I heard what sounded like a couple of phut sounds coming from the speakers and there was a strange smell. I switched off and taking it all apart I found that the run capacitor has leaked a lot of wax inside the transport. I've read some articles that suggest this could be the cause of the problem.

Any thoughts?

Also I've removed the capacitor the service book says its EC330401 MP 2uF 250 WV.AC.
Can anyone advise a replacement part.

Also equivalent capacitors on Maplin site have four terminals, this one only has three. Again any advice please!

I labelled it all up and took lots of photographs so I could reassemble it. I was hoping to find a straight swop capacitor.
Not such a big job as I thought taking it apart.

thanks

Alan
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Old 1st Nov 2016, 4:48 pm   #2
monaghana
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Default Re: AKAI 1721L run capacitor question

Hi I should have said the capacitor is in the service manual as EC330401 MP/C 2+1 uF250WV.AC (Lug type Uni/D.)
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Old 1st Nov 2016, 5:54 pm   #3
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Default Re: AKAI 1721L run capacitor question

The maplin motor run capacitors will have 4 terminals just because they're doubled up; it will be obvious if you look at the top of the capacitor that each terminal has 2 lugs on it, nothing to worry about. You use 1 from each side.

Quote:
MP/C 2+1 uF250WV.AC
not sure what the 2+1 means. Your previous post 2uF makes more sense ie 2 microfarads, 250 ac working volts, MP will be Metallised Polypropylene, a common material for motor run capacitors.
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Old 1st Nov 2016, 8:31 pm   #4
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Default Re: AKAI 1721L run capacitor question

Here's an extract from the service manual. 2 + 1 means 2uF and 1uF caps in the same package.
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Old 1st Nov 2016, 10:12 pm   #5
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Default Re: AKAI 1721L run capacitor question

I THINK? this is to do with voltage frequency, I have an old Revox and a Teac and both have two motor run caps (per motor), only one is used for 50Hz and both for 60Hz (or perhaps the other way round).
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Old 2nd Nov 2016, 11:17 am   #6
monaghana
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Default Re: AKAI 1721L run capacitor question

Hi thanks for this.

It looks like the 2uF is in parallel with the motor windings and the 1uF is in series. Some variations in the schematic only have the 2uF across the windings. Anyone know if I need both here in the UK or if a multi value cap is required?
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Old 2nd Nov 2016, 1:55 pm   #7
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Default Re: AKAI 1721L run capacitor question

makes sense
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Old 2nd Nov 2016, 2:16 pm   #8
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Default Re: AKAI 1721L run capacitor question

If it is configured like the motor on the Akai 4000 (2+0.5 uF) the dual capacitor is used in connexion with adjusting for 50Hz or 60Hz mains frequency. If you are never going to require operation on, say 60Hz, a fixed single capacitor of the value used on 50Hz will suffice i.e. 2.5uF. I can't be sure because I haven't got the full power input circuit but it may well be that for 50 Hz only use you could just use a 3.0uf capacitor.
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Old 2nd Nov 2016, 2:26 pm   #9
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Default Re: AKAI 1721L run capacitor question

Here's a bit more of the diagram.
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Old 2nd Nov 2016, 6:09 pm   #10
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Default Re: AKAI 1721L run capacitor question

It looks to me as though the 2 sections of that capactor are connected in parallel (giving 3uF) for 60Hz mains and only the 2uF part is used for 50Hz. So you could get away with only a 2uF capacitor for the UK/Europe.

However (and many will disagree with me) I wouldn't do that. The unit was originally designed to be switchable between 50 and 60Hz (I assume a pulley change or something is needed as well) and I feel that when you restore something you should keep _all_ original features. Even if they are never going to be used.
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Old 2nd Nov 2016, 10:46 pm   #11
monaghana
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Default Re: AKAI 1721L run capacitor question

I agree with TonyDuell. It would be good to replace like for like. I'll spend a bit more time searching for replacement.
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Old 2nd Nov 2016, 11:15 pm   #12
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Default Re: AKAI 1721L run capacitor question

I don't think you're going to find 2uF and 1uF capacitors in a single can.
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Old 3rd Nov 2016, 4:05 pm   #13
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Default Re: AKAI 1721L run capacitor question

There is a stepped flywheel which allows the belt to run on the larger diameter for 60Hz. This is controlled by the screwdriver slot adjustment plunger in the deck panel. For 50Hz the 1uf cap is unused, and not being an originality fetishist, I have disabled the rear panel switch, run on only 2uf so it's fixed on 50Hz. It's not such a rare and valuable machine that a few mods can't be done IMHO, and I would always be scared of accidentally knocking the cycle choice switch over to 60Hz by accident and causing damage
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Old 4th Nov 2016, 10:04 am   #14
monaghana
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Default Re: AKAI 1721L run capacitor question

Ok thanks everyone for the advice. I can get a 2uF run capacitor in Maplin for three pounds and I'll have a go at fitting that. The 1uF cap is also available which I could also wire up. Might take saxmaniac advice and disable switch. We'll see.

I'll stand well back when I power up. Will let you know how I get on.

cheers

Alan
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Old 5th Nov 2016, 3:57 pm   #15
monaghana
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Default Re: AKAI 1721L run capacitor question

I replaced the run capacitor and powered up. Nothing! Switched off and checked both fuses which were good. Then remembered the auto power off button. It was enabled so with no tape in transport it wont power up. Disabled this and all working fine.
New run capacitor £2.99
New soldering iron £9.99
Fixing it -- Priceless

I'll post a photo when I figure out how.

Many thanks everyone.

Now to see if I can improve the sound quality.
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Old 5th Nov 2016, 5:44 pm   #16
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Default Re: AKAI 1721L run capacitor question

Re posting a picture, click "Go Advanced", click "manage attachments", click "choose file" then "upload". Job done.

Well done for getting it fixed. Is this your first repair?

Andy.
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Old 5th Nov 2016, 11:22 pm   #17
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Default Re: AKAI 1721L run capacitor question

Here is before and after
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Old 25th Nov 2016, 2:46 pm   #18
monaghana
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Default Re: AKAI 1721L run capacitor question

Quote:
Originally Posted by Dr Wobble View Post
Well done for getting it fixed. Is this your first repair?
Hi Andy, sorry that was rude not replying to your question. First fix for a while. I used to be a computer service engineer years ago. I just watched your video on repairing a Revox A77 and heard your comments about PCs. I agree with you. I did work on equipment you had to strip down to repair, multi head disk drives following head crashes and big old vacuum chamber tape transports, but that was over thirty years back.

Alan
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