Tuesday, December 23, 2008

Float Your Screen Resistors!

Here's a pretty extreme example of what happens when you
screen resistors are too close to the pc board. This is why it's important
to "float" higher power resistors off the circuit board.

The amp here is an Ampeg V4B. The board was so burned that the
screen resistors were moved off to the power tube sockets.
The resistors that burned up were replacements,
the originals would have been underneath the pc board.

In the center of the picture below is a floated resistor in a
Fender Champion 600. The breathing room beneath
the resistor reduces the chance of the pc board being
damaged if the resistor overheats or flames out.

It's shocking that some new production amps don't bother
to do this as their pc boards are generally very delicate.
There is no really effective way to repair a pc board
once it goes. Your tech can kludge in jumper wires
but the amp will never be "like new".

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