F5 power amplifier

[bobodioulasso]

Originally Posted by bluewater

Would anyone have any input on why I would have 500mV pushing out my outputs on one of my channels?

Are you shure there is no dc at the input?

[bluewater]

the input is isolated from anything and the two output transistor are cool to the touch.

[CBRworm]

Originally Posted by bluewater

the input is isolated from anything and the two output transistor are cool to the touch.

That can't be good. Touching a cold amp is like holding a dead fish.

[compressit]

Bluewater, have you confirmed that both pots are at zero and re started the bias process from scratch?

[tinitus]

And prove sticks have been connected in the right place when adjusting?

[bluewater]

thank you for all the reply's.
no I haven't tried starting from zero mostly because it was working fine before this happened. I not sure if starting with the pots is the right course just yet.
tinitus, what do you mean by sticks?

[tinitus]

Originally Posted by bluewater

tinitus, what do you mean by sticks?

Oh, sorry
I wrote "prove" sticks, and it should have been "probe" sticks
Those things to connect multimeter to amp board
Isnt that what they are called?

What I was asking
Do you measure the right way?
Is multimeter used properly?
Connection point, meter setting etc.
Are your probe sticks in good condition?
I have to resolder mine frequently
Not the most reliable things
And sometimes a meter works fine with one setting and not with some other setting, cheap ones ofcourse, but thats what most of us can afford, but may not be completely reliable either

[bluewater]

they work fine and are in good shape. When adjusting the dc offset I connected them to the output and the output ground.

[tinitus]

Originally Posted by bluewater

When adjusting the dc offset I connected them to the output and the output ground.

I dont think you should do that without monitoring bias at the same time
As I understand it, its possible to "find" a bias a point where DC is low
But you cannot just turn bias pot to the lowest DC
It should be done carefully, bit by bit
And never turn bias pot only looking at DC
Output devices can go dead in a second without heatsink even getting hot

But now I talk about something Im not sure about, as I havent built my F5 yet

But I do remember to have done something similar, turning a trim pot without anything happening
Amp went dead before I realised I had been looking at the wrong meter setting

[bluewater]

While adjusting the offset I had another multimeter monitoring the voltage drop on r11 or r12.