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PostPosted: August 2nd, 2013, 3:16 pm 
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TubeDriver wrote:
It is odd that monoblocks would fail at the same time. I wonder about a power surge that shorted a small cap across H and Neutral or maybe fried the SS rectification?


Exactly what I was thinking.... :clap:

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PostPosted: August 2nd, 2013, 3:17 pm 
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Location: Potomac, MD
I suspect a rectifier diode has shorted, ironically in each one. I am guessing this because they blow the fuse even if the tubes are not installed if I understand you, bigthinker, correctly. Perhaps a line surge during a storm took them out?


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PostPosted: August 2nd, 2013, 3:22 pm 
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TubeDriver wrote:
It is odd that monoblocks would fail at the same time. I wonder about a power surge that shorted a small cap across H and Neutral or maybe fried the SS rectification?


Looking at the photo, it is not clear if there is a cap between hot and neutral at the IEC, though I think I can make out a dark disc shape below the wiring. I agree that it is highly unusual for both units to fail in the same way at the same time, and an external event such as a power surge would be a logical cause.

David


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PostPosted: August 2nd, 2013, 3:30 pm 
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David McGown wrote:
TubeDriver wrote:
It is odd that monoblocks would fail at the same time. I wonder about a power surge that shorted a small cap across H and Neutral or maybe fried the SS rectification?


Looking at the photo, it is not clear if there is a cap between hot and neutral at the IEC, though I think I can make out a dark disc shape below the wiring. I agree that it is highly unusual for both units to fail in the same way at the same time, and an external event such as a power surge would be a logical cause.

David



I also noticed that disc shape near the AC input wiring. Could be a small value, cheap ceramic cap?


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PostPosted: August 2nd, 2013, 3:35 pm 
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TubeDriver wrote:
David McGown wrote:
TubeDriver wrote:
It is odd that monoblocks would fail at the same time. I wonder about a power surge that shorted a small cap across H and Neutral or maybe fried the SS rectification?


Looking at the photo, it is not clear if there is a cap between hot and neutral at the IEC, though I think I can make out a dark disc shape below the wiring. I agree that it is highly unusual for both units to fail in the same way at the same time, and an external event such as a power surge would be a logical cause.

David



I also noticed that disc shape near the AC input wiring. Could be a small value, cheap ceramic cap?


That is what I suspect. The only problem is that if they shorted, they should take the breaker with them when plugged in. So it kind of rules that out as a possibility, since the fuse blows when turned on.

David


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PostPosted: August 2nd, 2013, 3:38 pm 
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David McGown wrote:
That is what I suspect. The only problem is that if they shorted, they should take the breaker with them when plugged in. So it kind of rules that out as a possibility, since the fuse blows when turned on.

David


Unless, and it's hard to tell from the picture, it's got one of those IEC receptacles with the fuse-holder built-in.... :confusion-confused: Need more :banana-gotpics:

Roscoe

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PostPosted: August 2nd, 2013, 3:57 pm 
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Hate to stick my nose into these things, but..... Safe to assume both are correctly connected to a speaker load without any shorts in the wiring?

Jim


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PostPosted: August 2nd, 2013, 5:24 pm 
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is it safe to assume that the poster does not have much electronics experience? If so, someone more knowledgeable may need to look at these...


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PostPosted: August 2nd, 2013, 5:42 pm 
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randy warren wrote:
is it safe to assume that the poster does not have much electronics experience? If so, someone more knowledgeable may need to look at these...


Probably. Patrick - I should be available pretty much any time Sat, and Sun after about 1PM if you want to make the trek all the way out here...

Roscoe

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Last edited by Roscoe Primrose on August 2nd, 2013, 5:43 pm, edited 1 time in total.
typo


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PostPosted: August 2nd, 2013, 6:31 pm 
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I appreciate all the response to this post. I do not have a lot of experience but I do own an Ohm meter, so I can respond to some of your recommendations. I was thinking it was the mains transformer. If someone knows of a reputable place to get them repaired or knows for certain how to repair this, please let me know.

Again, thanks for all the positive suggestions and thoughts on this problem.


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