"Franc Zabkar" wrote in message
...
On Fri, 24 Feb 2012 23:43:18 -0500, "John Smith"
put finger to keyboard and composed:

Before I replaced the chip I checked the voltage at all pins as follows.

6. 76.5
9. 3.2

AISI, the voltage across R372 (22K) must be 73.3V.

Therefore its power dissipation would be ...

73.3 ^ 2 / 22K = 244mW

However, the parts list rates it for 1/5W.

Thanks but this is one of the first things I checked before replacing the
device.
R372 does measure 22K.
I actually cut one of its legs to test it out of circuit because it's a pain
to get the board off the heatsink (all output FETs have to be unsoldered) I
then soldered its leg together again.

I spotted another potential design error.
Compare the TA7317 Vcc max with what I measured. This only affects pin 6.

I'll find out more when I get back to it on Monday.

old guy


- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.