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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 26th Dec 2017, 6:41 pm   #1
flake_e_lee
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Default Sony MDS JE480. Hum.

Hi all,new here and in all honesty I signed up as this has me stumped, just being honest.

I play part time in a two piece group and the mini disc set up has and still is popular for guys like me to use for our backing tracks. Normally we use an Amazon Kindle/MP3 set up but I acquired a Sony MD player recently and 200 backing tracks with it.

So, it came as a non runner .It powered up but no output from the RCA connectors. Took it apart and the RCA outlet was loose into the board so I soldered those back in. Took the md player to the PA system and hooked all up RCA to RCA. Yes, the MD player works but with a bad 60 cycle hum which is worse when I put the MD player in standby.

It is a steel cased item and if I unplug the RCA plugs from the MD player I get no hum. I took it apart and as a process of elimination,I unplugged the ribbons from the drive and the control panel. The hum was still there so its one of two things, pre-amp section (this machine has no power-amp, it needs a seperate amp) or the transformer.

Any help to eliminate my hum greatly appreciated as this machine will be a great asset to us for gigs.

Thanks in advance!

Last edited by flake_e_lee; 26th Dec 2017 at 7:06 pm.
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Old 26th Dec 2017, 6:54 pm   #2
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Default Re: Sony MDS JE480. Hum.

Quote:
Originally Posted by flake_e_lee View Post
Yes, the MD player works but with a bad 60 cycle hum which is worse when I put the MD player in standby!
I think you mean 50Hz hum? 60Hz mains is used in the US and some other countries, but not in the UK.
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Old 26th Dec 2017, 7:04 pm   #3
flake_e_lee
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Default Re: Sony MDS JE480. Hum.

I stand corrected, its a god-awful hum, worse in standby mode
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Old 26th Dec 2017, 8:43 pm   #4
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Default Re: Sony MDS JE480. Hum.

I have an MDS-JE440 here which works fine but the disc loading and unloading is getting a bit arthritic. If you're getting bad hum, I'd wager that the ground connection on the phono sockets is broken. Double check that you've resoldered the connection to the outer ground contact as well as the inner signal contact. The fact that the connectors had come loose implies that they might have had a knock at some time. There should be a screw holding them to the back panel and providing some support. Is that still present? Check carefully for cracks in the PCB around where the connectors are soldered. If it's had a bump, a crack in the board is very likely. It's pretty fragile.

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Old 26th Dec 2017, 9:10 pm   #5
flake_e_lee
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Default Re: Sony MDS JE480. Hum.

Board looks pretty good to me and damage free, and screw is still in position that holds the in/out RCA jacks.
I will unscrew this thing and take a few photos and put them here later tonight.
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Old 26th Dec 2017, 10:47 pm   #6
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Default Re: Sony MDS JE480. Hum.

A few photos of the board, now removed from the MD.
Also removed the jack sockets from the board.
Four tags straight on to the board, soldered in and I assume its negative output is directly from the chassis?
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Old 27th Dec 2017, 12:28 am   #7
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Default Re: Sony MDS JE480. Hum.

Does it have a headphone socket and, if so, does it hum if you listen to some headphones plugged in to it?
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Old 27th Dec 2017, 1:35 am   #8
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Default Re: Sony MDS JE480. Hum.

No headphones socket, only the RCA out to the amp.
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Old 27th Dec 2017, 7:58 pm   #9
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Default Re: Sony MDS JE480. Hum.

OK.

I had another closer look today, tried a theory and it worked. The hum is gone.

I noticed, the 4 pins on the RCA plugs that go into the board. I saw what looked to me where there had been a further 2 pins which had been sheared off at some point and a corresponding position on the board where 2 pins probably were soldered to it. I cut the legs off a capacitor, soldered these to the RCA plug and then soldered all back on to the board. Assembled the unit, hum gone!

Now if I could get a new plug, as I do not fully trust my repair. I think if it gets any type of knock, it will break the repair and back to the hum. Anyone know where I could get the plug?
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Old 27th Dec 2017, 8:18 pm   #10
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Default Re: Sony MDS JE480. Hum.

I would not worry your repair is probably better than the original flimsy arrangement.
Well done.
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Old 27th Dec 2017, 8:30 pm   #11
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Default Re: Sony MDS JE480. Hum.

Excellent, thank you for the update. I'm glad to hear it's fixed. As Peter says, your repair is probably at least as good as the original!

Enjoy using the Minidisc machine,

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Old 27th Dec 2017, 9:52 pm   #12
flake_e_lee
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Default Re: Sony MDS JE480. Hum.

LOL, as long as it does not get a hard knock or any abuse in the RCA jack area hopefully it will last.

The only thing that came to mind for me to use in the repair were the legs from a cap and they seem to have worked.

I'm unfamiliar with the MD set up but hoping we can add our backing tracks stored in the computer onto discs and use the whole set up at gigs.
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Old 28th Dec 2017, 1:07 am   #13
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Default Re: Sony MDS JE480. Hum.

Thanks all for input here.

With me being heavily involved in musical gear, I'm pretty sure I will be a regular back and forth when I get stumped as I repair as much of my own gear when possible from guitar amps( last repair on one was fit 4 field transistors in the power amp board) to mics.
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Old 29th Dec 2017, 12:10 pm   #14
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Default Re: Sony MDS JE480. Hum.

Hello, I may well be wrong as my eyesight is not that good but the joint by R177 looks iffy. If I am wrong and it is a shadow or something then sorry, please accept my apology.

Cheers.

Geoff.
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Old 29th Dec 2017, 3:58 pm   #15
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Default Re: Sony MDS JE480. Hum.

I too am a dedicated minidisc user. I use them for backing tracks for theatre shows I do sound and light for. Theatre techies laugh when I drag the MDS-JB930 out and set it up in front of the lighting desk and I'm often asked why don't I use a computer. Well my answer is this: A. laptop has too large a footprint. B. doesn't load the next track ready for playing after the previous one has finished and C. does not display a large enough time clock to use for to the second lighting changes required by most of the shows I'm involved in. Yes, we could probably automate a lot of the lighting but that relies on the cast doing things exactly the same way every time and there is no "feel" with automation. I like the on the fly editability you get with M.D. I also use it for Panto sound effect playback too. Now, I'm sure software does exist that will do what I need (big time display, auto track advance etc) but at what cost? so as far as I'm concerned, Minidisc is here to stay.
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