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Question B&O Beolab 4000 Mk2 Transistor ID

 
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Last Post by Jayceebee 9 months ago
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Jayceebee
 Jayceebee
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A call over the fence came from my neighbour yesterday, one of his B&O active speakers was making a very odd chirping noise. Cutting to the chase something catastrophic had gone on as there are many components toasted on the very busy class D audio output board and damage to the multilayer board itself. I downloaded the manual but there are no circuits at all, it appear that the unit is board replacement only unlike the Mk1 for which had full circuit information.

The amp board is available as exchange for around £300 but I've found the PSU has slight damage also and again is around £300. The issue with the PSU is the + & - 12V supplies are switched and a transistor in the +12V feed is s/c. It's an 8 pin Fairchild (?) device and has the markings AH6AH FDS 4435. Searching the net has failed to show any answers. Any suggestions?

IMG 0249

John.

 
Posted : 21/07/2024 4:33 pm
crustytv
 crustytv
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Posted by: @jayceebee
↑

The issue with the PSU is the + & - 12V supplies are switched and a transistor in the +12V feed is s/c. It's an 8 pin Fairchild (?) device and has the markings AH6AH FDS 4435. Searching the net has failed to show any answers. Any suggestions?

I searched just using the part type id FDS4435, it brought up loads, a 30V P-Channel PowerTrench MOSFET

Datasheet https://www.mouser.com/datasheet/2/149/FDS4435-1008306.pdf

Mouser have them 80K in stock https://www.mouser.co.uk/ProductDetail/onsemi-Fairchild/FDS4435BZ?qs=GXuM9q1TrDl7P7R1rhmrgw%3D%3D

As do Farnell https://uk.farnell.com/on-semiconductor/fds4435/mosfet-p-so-8/dp/9846204?CMP=GRHB-SF-FC

Oops Obsolete at Farnell

Lots available via e-Bay and AliExpress, but I'd be wary of them, they must be prime targets for forging to fleece all those B&O folk with deep pockets.

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Posted : 21/07/2024 4:54 pm
Jayceebee
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@crustytv Thanks Chris, now why didn’t I try that! I’m often accused at home of looking with my eyes closed and it would seem to be the case here. I can at least test the repaired PSU in the other speaker before purchasing the amp PCB. I might just post in the wanted section for the amp in the slim hope anyone has one.

John.

 
Posted : 21/07/2024 5:35 pm
crustytv reacted
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