Line voltage selector Revox B750 MK II blew up - diyAudio
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Old 20th May 2011, 09:38 PM   #1
BrianVG is offline BrianVG  Belgium
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Default Line voltage selector Revox B750 MK II blew up

Hi all,

I thinks this fits in the power supply forum.
I was listening to my Revox B750 when I suddenly saw smoke, lots of smoke!
I instantly turned the amp off and pulled the plug out. We were afraid that the whole thing was on fire because of the smoke (the room was really full of it).
The smell of the smoke was really bad, my first tought was that a big cap blew.
After opening some windows, I opened the amp.
I could see the problem in an instant.

Click the image to open in full size.

It has something to do with the voltage line selector.
Right now the selector is set to 240VAC (Belgium => 240VAC, 50Hz)

As you can see this 'thing' has caugt fire, the only thing I read on it was

"250V, fo 9MHz"

What is this component?

Also: the fuse is not blown and the music kept playing when smoke was coming out.
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Old 20th May 2011, 09:43 PM   #2
BrianVG is offline BrianVG  Belgium
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Click the image to open in full size.
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Old 20th May 2011, 10:21 PM   #3
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Looks like a noise suppression capacitor, X or Y type.
The dielectric got compromised, just snip the leads and remove it.

If you really want, replace it with the proper type, around 100nF (try to see the rating of the original one). Type X if it does not go to ground (most likely). Type Y if it does.
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Old 20th May 2011, 10:26 PM   #4
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Looks like a noise suppression capacitor, X or Y type.
The dielectric got compromised, just snip the leads and remove it.

If you really want, replace it with the proper type, around 100nF (try to see the rating of the original one). Type X if it does not go to ground (most likely). Type Y if it does.
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Old 20th May 2011, 10:33 PM   #5
BrianVG is offline BrianVG  Belgium
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Quote:
Originally Posted by discrete View Post
Looks like a noise suppression capacitor, X or Y type.
The dielectric got compromised, just snip the leads and remove it.

If you really want, replace it with the proper type, around 100nF (try to see the rating of the original one). Type X if it does not go to ground (most likely). Type Y if it does.
Will a WIMA MKP capacitor do the job?

Click the image to open in full size.

I've used them in some amps, they are alot smaller than the cap I blew.
I've got my hands on the schematic of this amp. Maybe this could say what value it was.
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Old 20th May 2011, 10:41 PM   #6
BrianVG is offline BrianVG  Belgium
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Click the image to open in full size.

100nF indeed, thanks discrete!
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Old 21st May 2011, 12:25 AM   #7
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Quote:
Originally Posted by BrianVG View Post
Will a WIMA MKP capacitor do the job?
NO!

Has to be an X-rated type (not what you think...).
Try to get X1, if not X2 is ok.
http://www.vishay.com/docs/28117/mkp3361.pdf

You can also safely leave it out, at the risk of picking up some electrical noise through the mains feed.
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Old 21st May 2011, 08:15 AM   #8
BrianVG is offline BrianVG  Belgium
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I'm not familiar with X or Y type capacitors.

I went on a searchs in my recycled component. And I found one it has X2 printed on it, the value is 330nF

Click the image to open in full size.
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Old 4th August 2011, 04:03 PM   #9
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I had the same problem a few days ago. i must need to change component or i can use this amp without ? voltage must be set to 240 VAC?
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