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tranny problem, looking for advice on a power amp
john11
post Mar 23 2013, 08:47
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Hi and thanks for reading this post.

My amplifier has been playing up on me and i noticed a swollen capacitor which i replaced with a new one of the same voltage and capacitance.

When reassembled the amp would not work at all, after a few hours of experimentation i noticed a row of transistors which are clipped onto the metal chassis of the amp, obviously this was done by the manufacturer to keep the transistors cool and i had to unclip these to get the board out.

When the transistors are clipped back onto the chassis of the amp so in effect they are all sharing one large heatsink the amp does not work, i gave each transistor its own heatsink and now the amp works fine.

Can anyone tell me what is going on.

Many thanks in advance. John.
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DonP
post Mar 23 2013, 14:56
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Uneven temperature would not be an instant effect, so if with the single chassis heatsink the amp is just dead, then there must be an electrical difference. Were some of the transistors originally isolated from ground?(sometimes done with a ceramic spacer)


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DVDdoug
post Mar 24 2013, 05:44
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QUOTE (DonP @ Mar 23 2013, 06:56) *
Were some of the transistors originally isolated from ground?(sometimes done with a ceramic spacer)
Right... Or, sometimes it's a mica insulator. If all of the transistors are on the same heatsink, they will have to be isolated. The "cases" of the transistors don't all share a common connection.
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