threshold s/450e bias

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
Perhaps he is living up to his name....

There will be a bias pot for each channel. You can read the voltage off
of the emitter resistors of the output transistors which I recall to be 1 ohm.

Check several of them. The S450e has 6 of those in parallel, so the
bias current with the 1 ohm resistor is 6 times the voltage you read.

.1V = .6 amps bias

You will want to be careful, as you can damage the amp or yourself
doing something like this. Make adjustments in small steps and allow
the amp to sit with the cover on for a while before re-checking.

Best advice - bribe a technician to do it for you.


Paid Member
2013-01-30 4:15 pm
Elkhart Lake, WI
You may want to buy the rubber high voltage gloves technicians use on electric/hybrid cars. You can find them at most electric supply stores.
They are bulky and uncomfortable, your hands will sweat inside them, however, it sure beats accidentally touching 78 vdc, That kind of early retirement is not what it's cracked up to be.

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
What voltage do I have to have in each of the 1ohm resistors?

I would start with .1V and see how hot that gets the amp.

And you can use the following guide to get to 50 deg C.


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