405 Fuse blows

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26-Jun-2019 10:08 AM

lool

lool

Posts: 4

Due to a problem with my pre-amp (to high voltage on the output channel), the left channel of my 405 blew it's fuse #1. After replacing it, the fuse blew again. So probably there's more broken on the board. Any idea where to look ?
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26-Jun-2019 01:13 PM

Stefaan

Stefaan

Posts: 601


It looks like one or more of the power-transistors in the faulty channel is blown.

I would check all the transistors with a multimeter.

Replacement-transistors are here: http://www.dadaelectronics.eu/FAQ.htm

You can also send the board to Dada for repair.

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26-Jun-2019 02:23 PM

lool

lool

Posts: 4

And with power transistors you mean TR7/8 and TR9/10 ?
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26-Jun-2019 03:42 PM

Stefaan

Stefaan

Posts: 601


TR9/10 are the power transistors and TR7/8 are the drivers.

Best is to measure them all.

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26-Jun-2019 04:15 PM

lool

lool

Posts: 4

Thank you for the info Stefaan. Could I replace the power transistors with a pair of 2N3055 I still have laying around ?
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26-Jun-2019 05:02 PM

Stefaan

Stefaan

Posts: 601


Hello,

No, 2N3055 does not have enough power. You should use MJ15003.

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28-Jun-2019 09:58 AM

lool

lool

Posts: 4

Looks like one of the MJ15003 got fried. Just ordered a new one. Thx Stefaan.
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