Amplifier died after working for a while!!!!

Hi people,

I made a amplifier following the Project 3A ( link is

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I make some chnages such as replace current source to a mirror current source, and added some big capacitor at the power supply.

When it worked, it is really nice, but last about one hour and it died. I replace some died power transistor, and test again. I try to increase the quiesent current by adjusting the pot VR1, and it broken again.

Can someone explain for me? What did it do like that?

I am looking forward hearing from people soon!!!

Van Hau

Reply to
Himlam8484
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I would start by measuring the quiescent current in the output and driver transistors. Also, see if there is any DC current flowing to the speaker.

Tam

Reply to
Tam/WB2TT

Sounds like thermal runaway. Did you thermally couple Q9 to Q5 and Q6?

Q9 is supposed to do thermal compensation of the output quiescent current.

Reply to
nospam

for one thing, the VR1 is there to reduce the current to it's minimum and most likely used to balance the output to 0 volts with no signal on the input while making adjustments.

You don't show how you have mounted your power transistors?, I do hope you are using heatsinks? And I hope you are monitoring the heat level ..

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Reply to
Jamie

It most likely burned up with excessive bias through the output transistors... This is not a good design, there is no necessity for bootstrapping the output stage in a modern circuit...

Reply to
Fred Bloggs

"Fred Bloggs

** Bollocks.

** ROTFLMAO !!!!!!!!!!!!!!

Slaves to audiophool, voodoo inspired fashion are asinine fuckwits indeed !!!!!!!!!!!!!!!!!!!!!!!!!!!

The Bloggs congenital, autistic, MORON regularly obliges, on cue - as usual .......

Bowel cancer is too good.

...... Phil

Reply to
Phil Allison

Perhaps you would have been better to have built and tested the design as given before trying to improve it with your own modifications. . . .

--
John B
Reply to
John B

when i did not connect a speaker, i can not measure the voltage drop across power resistor.

Reply to
Himlam8484

Yes I have one, but I think the problem may be there. When the heat increases more and more then the amp die. Today i will make the board with the enough big.

Reply to
Himlam8484

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