On Jun 29, 7:02*pm, "Phil Allison" wrote:
** I have a Line 6 " Spider II " amp in the workshop (this is the head only
version and removing the chassis seems impossible until you discover the
trick with the front panel). It came in completely dead with both power ICs
blown.

....
A finger test revealed that each TDA was getting very hot after only a few
seconds while the heatsink was still essentially at room temp. Tested with a
K type thermocouple, the mounting tab reached 90C in just over 1 minute and
would clearly soon exceed 100C as the heatsink warmed. This is not good.

Being suspicious of the stick-on thermal pads, I decided to remove them and
fit mica ones instead, aided by silicone grease. ( Pealing off the original
pads revealed a thick film of adhesive on the heatsink which had to be
scraped off and rubbed clean with solvent).

Was this adhesive meant to be thermally conductive? Or did the
assembly house just use whatever was on hand to get the work out?



BTW:

The reason for the dual channel failure is almost certainly that the owner
plugged both outputs into the same speaker cab.


Forgive my ignorance of musical instrument speakers, but why would the
cabinet have been designed to make this possible, given that Murphy's
Law is in full force?