No Clue wrote:
"John Popelish" wrote in message
...
No Clue wrote:

Here's some pics of the inside. It's a Yamaha G100-112III guitar amp.
I've
circled the resistor in yellow, and red dots on back of circuit board
where
it connects.
Is it possible for you to read any part number on the small
black rectangular block a half inch from the resistor, that
has 9 pins in a row? The resistor seems to be connected to
it and the black 24 VDC relay block.


The numbers on the side of that block are a large (T), then TA7317P - 4E.
The 4E is a lot smaller than the rest of the numbers. I marked the pic with
a red arrow to make sure we're talking of the same block.

You got it. That number (TA7371) allowed me to Google for
the data sheet.

Hit "download data sheet on:
http://www.datasheets.org.uk/search....317&sType=part

It looks like this resistor is approximately the same one
that connects pin 6 to the relay coil on page 3 of the data
sheet (500 ohm 3 watt). The value may be different, because
the supply voltage is different. It uses up all the extra
supply voltage that exceeds that needed to operate the 24
volt relay. The relay coil may have partially shorted out,
causing extra power to be dumped into this resistor.

The voltage between pin 6 and pin 4 should be either about
1.2 volts (when it is turning the relay is on during
operation) or the full supply voltage (when the protection
relay is off for a while at start up, to prevent a big
speaker thump). This is the output voltage speced on page 1
to be typically 1 volt and not more than 2.

Can you measure the voltage across the resistor and provide
its color code (looks like orange, something, black gold),
so we can figure out whether its (and thus, the relay coil)
current is reasonable?