Arcam delta 290 p working but distorted sound

homertooties · 21st September 2008, 10:28 AM

Hi everyone currently repairing an Arcam delta 290

I channel was down blowing mains fuse ,replaced the fets with new irfp240,fixed no more dc problems ,i get music but when i try and turn
up the amp the sound is distorted,,i also replaced pre driver transistors......

Bias is correct ,altering it makes no difference,changed preamp chip also still same....

Thanks to anyoone,.

AndrewT · 21st September 2008, 10:54 AM

Hi,
check the Vbe voltages of all the transistors.
If they are around 600mV+-50mV, then that probably indicates they have not been damaged.

The exception will be any protection transistors which may run with Vbe <<=400mV

jaycee · 21st September 2008, 04:04 PM

Chances are when the fets went, the drivers got damaged - replace them.

Mooly · 21st September 2008, 04:31 PM

Fried speaker from previous fault ?

21st September 2008, 10:28 AM	#1
homertooties diyAudio Member Join Date: Nov 2005 Location: suffolk	Arcam delta 290 p working but distorted sound Hi everyone currently repairing an Arcam delta 290 I channel was down blowing mains fuse ,replaced the fets with new irfp240,fixed no more dc problems ,i get music but when i try and turn up the amp the sound is distorted,,i also replaced pre driver transistors...... Bias is correct ,altering it makes no difference,changed preamp chip also still same.... Thanks to anyoone,. __________________ if you strip it for parts keep them for years as soon as you get rid you will want them .....................

21st September 2008, 10:54 AM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, check the Vbe voltages of all the transistors. If they are around 600mV+-50mV, then that probably indicates they have not been damaged. The exception will be any protection transistors which may run with Vbe <<=400mV __________________ regards Andrew T.

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21st September 2008, 04:04 PM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	Chances are when the fets went, the drivers got damaged - replace them.

21st September 2008, 04:31 PM	#4
Mooly diyAudio Member Join Date: Sep 2007	Fried speaker from previous fault ?

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