It's a frequency identifier. How can I test it? Is it replaceable or
even worth it?

James Sweet wrote:
Alec S. wrote:
Hi,

I have a Matrix auto chromatic tuner-to tune instruments-model
SR-4000.

A while back I killed it by-accidentally, I swear!-plugging in a
power cord which was set to a few volts too high (12v instead of 9v)
backwards (reversed polarity).

I would like to fix it. I would like to diagnose the problem and if
I'm lucky repair it (I assume it's a dead component that needs to be
replaced.)

While I am no electronics expert, I am also not a novice. I have
repaired computer hardware (and built a few parts of my own), and even
our home's wiring (although that's really just dangerous, not complex.)

I've got a digital multimeter, variable power supply, all kinds of
wires, alligator clips, etc, hopefully pretty much any tools I might
need. I've also got a large box full of electronic part potpourri that
I got from various places including a supplier a long time ago and from
various electronic devices I've cannibalized.

I have scanned the circuit board and they can be found he
http://img378.imageshack.us/img378/4...erfrontbo8.png
http://img230.imageshack.us/img230/8...nerbackag3.png

I've tried running a couple of small tests, but I don't really know how
to test something like this. For example, I'm not certain how to test
if a transistor is good (I've got an idea but I'd rather hear from
experienced people), or a quick connectivity test reveals nothing
useful since pretty much everything seems to be connected to everything
else, and testing for power returns all kinds of variable voltages that
tell me nothing.

Does anyone have any tips or advice (or maybe a complete walkthrough?)
on how to test and repair this?


Thanks a lot!



It doesn't look like there's any regulator or protective circuitry on
the power input, I wouldn't be surprised if the reverse polarity killed
the microcontroller or whatever that large Intel chip is.