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Electronics => Repair => Topic started by: thomastorm on July 10, 2016, 08:32:27 am

Title: Yamaha DX 7 overheated and no sound
Post by: thomastorm on July 10, 2016, 08:32:27 am

Hi everybody
I forgot to switch off my DX 7 for days and i found it overheated and with no sound.
What can i do now?
Thanx

Title: Re: Yamaha DX 7 overheated and no sound
Post by: Totalsolutions on July 11, 2016, 08:35:30 am

Hi, Mk II .... ? Not much to go on. Have you checked the PSU (power supply unit), if its that old a keyboard and has a external power brick more likely the transformer overheated only, open circuit to the internal thermal fuse.

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Title: Yamaha DX 7 overheated and no sound
Post by: Totalsolutions on July 11, 2016, 08:39:08 am

Check out youtube  user "fredturd" Yamaha DX 7 Battery Repair  Tips #1

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Title: Re: Yamaha DX 7 overheated and no sound
Post by: Jr460 on July 11, 2016, 11:02:18 pm

Is this a DX7 or the DX7IID/DX7IIFD?

Years ago I had my 1987 DX7IID go dead.  Power supply was the issue.  The local repair shop really didn't want to touch it but said most likely the big 5W resistor in PS opened up, it was a common fault.  The supply is internal, a separate module from everything else in t he unit.  Even the original DX7 didn't use a wall wart/plug pack.

Opened it up, measured, and sure it was open.  I forget the value of it, something like 2.5 Ohms 5W.  I could find that exactly but found to resistors at 5W that paralleled was very close to the value I needed.  Whacked it in, and it has been working fine for the past 15 years or more.

Title: Re: Yamaha DX 7 overheated and no sound
Post by: bitseeker on July 12, 2016, 01:59:22 am

Correct, internal power supply. That's the best place to start the investigation on most dead devices, keyboards included.