"Puddin' Man" wrote in message
...
On Thu, 19 Aug 2010 19:51:55 -0700 (PDT), wrote:


A simple voltmeter can give a lot of information particularly while
it's in 'failed' mode. While power devices (transistors and the main
audio power IC) can go 'thermal, I haven't seen a thermally sensitive
transistor in many years. The most common way back when was the TO-220
case devices - just like Q 701,702 and 705 but I would put money on
bad solder joints.

On the similar SA-160 which has 2 regulator transistors on the main
heat sink, all 6 terminals were cracked loose. After re-soldering
those I unsoldered the main power IC and resoldered it too since it is
mounted the same way as the transistors. Surprisingly, none of the
foil pads were damaged.

If you could render just a rough break-down of what was involved
in resoldering the 6 terminals, it would be very much appreciated.

Thx,
P


Reworking cracked joints on a practical level involves no more than applying
a nice hot iron to the side of the joint, then when the existing solder
melts, running a small amount - no more than 2 or 3 mm - of new flux-cored
solder into the molten joint. Hold the iron on the joint for a further 1 to
2 seconds, then slide it quickly away. This should leave a nice shiny joint
(assuming this is standard leaded solder) with no signs of a crack,
dullness, or crystalline appearance. If you want to be really pedantic about
the job, you can remove the existing solder first, before making a new joint
with fresh solder, but in order to do that, you would need at the very least
some solder wick, and if you lack the soldering experience to be able to go
for this repair without checking on the best way to go about it first, I
guess that it's going to be unlikely that you have any, or the experience to
use it to clean the joint.

If you just go ahead and do it as I have described, you should be fine.

Good luck with it

Arfa