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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 8th May 2020, 4:24 pm   #1
Whaam68
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Default Akai GX-46D

Hi
I picked this Early Akai top loading deck Up for £12 as a bit of a sacrificial unit So that I can hopefully learn more about working on cassette decks without wrecking anything too valuable. Externally it’s rough, scratched metal and missing veneer but internally it’s fairly clean and it actually sounds very nice ....everything still works apart from the bulb in the green Dolby indicator. However it runs slow on playback (rw & ff are ok) and while I have a test tape I don’t need it to hear the slow speed as it’s obvious. I replaced the 3 belts using some Near equivalents from an eBay selection pack and treated all the idlers to a coat of rubber refresh (they weren’t in bad shape to start with) and cleaned and greased/lubed the mechanism. I also cleaned the heads and transport and re lubed the flywheel(?) bearing that drives the main belt as it looked dry). This didn’t sort the slow speed and although the belts were a bit dry they were probably ok but it was good experience. This unit has a whopping big motor which I think is A/C rather than DC. It does however make a gentle thrumming through the deck that’s only audible when it’s not playing. Does anyone know if the speed is adjustable on this deck? And I can’t imagine the motor thrummed from new like that so is it likely to simply need a power supply refresh or does it suggest something more sinister? Also is the big Silver 1 & 6 uf cap the “motor run” cap? I haven’t tested it yet but if it needs replacing is this just a standard electrolytic? I have found a service manual which is on the way but thought I’d ask. Efore anyone mentions it it’s actually a GXC-46D!
Thanks
Mike
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Old 8th May 2020, 5:01 pm   #2
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Default Re: Akai GX-46D

Having looked again I can see what I think is the motor run cap is MP so presumably metallise paper so presumably replace with polypropylene these days.
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Old 8th May 2020, 6:58 pm   #3
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Default Re: Akai GX-46D

Hello Mike,

Nice looking and a good buy for £12 !

Yes AC motor with no obvious speed adjustment. Do not actually know what MP stood for on the old metal can Run capacitors, pretty sure they would have been paper dielectric, so maybe Metallized Paper. Modern versions would be MP/MPP (Metalized Polypropylene).

They are not electrolytic and are non polarised.

If you do need to replace the run capacitor, you do not need the 1uF + 6uF double can, probably difficult to find a new double can version anyway, if you are only going to run it on UK 50Hz mains.

Looking at the electrical schematic the 50Hz mains frequency selection switch connects both capacitors in parallel, which gives a total capacitance of 7uF. So for 50Hz operation only, you would need 7uF or somewhere close.

It should be a run capacitor rated for continuous use on AC voltage and be rated at least 300 volts AC, a lot of decent ones will be around 450 volts AC rated.

If the old run capacitors have degraded, it may be possible that could be the cause of the motor issue, without tying new capacitor, impossible to be sure.
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Old 8th May 2020, 7:38 pm   #4
Ted Kendall
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Default Re: Akai GX-46D

Agreed - change the motor cap first, and this may very well right matters. It's worth a bit of work - a 46 was my first cassete deck, and the tapes it made still sound pretty good.
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Old 8th May 2020, 10:08 pm   #5
Whaam68
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Default Re: Akai GX-46D

Thanks both
I have ordered the caps....managed to find polypropylene square section motor runs in the right values the two for a fiver ....if they arenít too big I will re stuff the can or if not I will work something out. Did some reading up on A/C synchronous motors and can now see why this cap might be the cause of the problem!
Mike
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Old 9th May 2020, 2:17 am   #6
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Default Re: Akai GX-46D

Yes a poor motor cap it could be. Silly question but is the machine set mechanically for 50 Hz? Many had a different sized pulley for 50Hz or 60 Hz operation.
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Old 9th May 2020, 6:27 am   #7
Whaam68
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Default Re: Akai GX-46D

Hi Tim
There is a Dual position switch near the motor with 50/60hz marked.....it’s set at 50hz. Would it still have the option of two pulleys if it has the switch?
Thanks
Mike

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Old 9th May 2020, 8:59 am   #8
Ted Kendall
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Default Re: Akai GX-46D

It should - the value of the capacitor is dictated by the phase shift needed for efficient operation, and the synchronous speed of the motor is 20% higher at 60Hz than at 50 Hz, hence the dual diameter pulley. For example, the Akai 4000 series has a switch on the back for the capacitor and a front panel screwdriver control for the belt setting.

Last edited by Ted Kendall; 9th May 2020 at 9:06 am.
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Old 9th May 2020, 9:17 am   #9
Whaam68
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Default Re: Akai GX-46D

Cheers Ted
When Royal Mail finally deliver it I should have a copy of the service manual and will check to see what it says about the pulley for 50hz operation. Didnít see anything obvious that jumped out at me.
Mike
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Old 9th May 2020, 9:30 am   #10
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Default Re: Akai GX-46D

Mine has a little door on the bottom with a belt on a stepped pulley, mines on the bottom one

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I got the service manual from a helpful member of the forum

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Old 9th May 2020, 9:38 am   #11
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Default Re: Akai GX-46D

Thanks Defender that is very helpful. I will go & check it! I am learning something!
Mike
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Old 9th May 2020, 10:06 am   #12
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Default Re: Akai GX-46D

Relevant page fr0m the manual.
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Old 9th May 2020, 11:00 am   #13
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Default Re: Akai GX-46D

Thanks again all....the give away should have been the sticker on top of the motor that I seem to have not noticed when doing the belt yesterday! Iíve re set the belt on the other pulley step it and itís now about the right speed. It was running slow when I got it. The thrum is still there though so Iím still going to replace the motor run cap.
Mike
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Old 9th May 2020, 11:21 am   #14
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Default Re: Akai GX-46D

Hereís a pic of the outside very ratty ...metalwork it looks like someoneís previously tried to polish with an abrasive.... & a couple of missing knobs ....Iíll keep on the look out for a doner replacement panel

The vu meters work very well but the red paint is coming off both of the needles....presumably from years of violent flicking about!

And the obvious sticker I missed....sorry about that!

I do like the laid back fuller sound of this deck compared to my old 1980s technics ....itís very easy to listen to & is a good match for the Armstrong 521. Ive had the technics since the 80s got it out to do a comparison.

Mike
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Old 11th May 2020, 7:28 pm   #15
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Default Re: Akai GX-46D

Thought you may like to see my Akai GX46D from a picture of me and my system from 1976. The Philips N4450 features a lot in this forum, could be troublesome.
Used the Akai till the early 2000ís, then we had motor issues. Replaced with an Aiwa which is easily forgotten!
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Old 13th May 2020, 1:02 pm   #16
Whaam68
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Default Re: Akai GX-46D

That's a great pic Arthur! Like the set up & the period "flares"...I've got a Leak badged Lenco exactly like that in storage up in the loft! Still waiting for my replacement motor run caps as the post at the mo is very slow. Then I'll get cracking on it. Hopefully that will quieten down the motor on mine.
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Old 13th May 2020, 10:41 pm   #17
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Default Re: Akai GX-46D

Quote:
Originally Posted by Whaam68 View Post
That's a great pic Arthur! Like the set up & the period "flares"...I've got a Leak badged Lenco exactly like that in storage up in the loft! Still waiting for my replacement motor run caps as the post at the mo is very slow. Then I'll get cracking on it. Hopefully that will quieten down the motor on mine.

I saved up for a Delta 30 but in the end got the 70 and the Leak version of the GL75 was a few quid cheaper than the Goldring GL75 and came with a G800E cartridge. My uncle still has the Delta 70 and tuner and a pair of Ditton 25 speakers!

Sorry donít want to go off topic with nostalgia!
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Old 23rd May 2020, 6:16 pm   #18
Whaam68
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Default Re: Akai GX-46D

Update on the Akai top loader....fitted the replacement poly motor run caps ...not the prettiest installation but it works! Caps are contact cemented in. Also fitted the correct belts and refreshed all the rubber idlers with truly stinky ďrubber RenueĒ. Speed seems really good now but hard to say how much is down to the caps and how much the belts. Iíve oiled the base of the capstan with turntable bearing oil applied with a syringe when itís spinning then cleaned the capstan with isopropyl as thatís where the gentle thrum is still coming from ....cant hear it at all when itís playing but itís there when it isnít. Is that normal for these A/C motor decks? It does sound nice and apart from the Dolby green bulb everything works well. Managed to improve the fascia panel using oil on a scrubby pad.
Mike
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