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Posted to sci.electronics.repair
Franc Zabkar
 
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Default Optoelectronics Scout 40 with reverse power damage

On Fri, 07 Apr 2006 20:05:35 -0400, NightRunner
put finger to keyboard and composed:

Interesting news with this little bugger... I have it almost repaired!
Thanks to Franc's post, I got out two irons and very gently removed
the regulator chip, and found as I should have forseen that this had
zero to do with the unit being dead. The regulator's only job is to
lower the 12v adapter voltage to 5v so it can run the unit without
smoking it yet again. The real damage remained at that point unseen,
and might have plagued me MUCH longer except that a tiny glint of
copper caught my eye between the power and filter switches, and on
closer inspection I discovered that it was another heat stressed part
of the board. I very gently removed a large diode that this heat
stressed trace ran beneath, and discovered much to my joy that it was
completely burned in half. I then took a small piece of wire and
completed the circuit with external batteries powering the unit, and
presto, it powered right up, and ummm... stayed powered even after I
removed the jumper wire. It must be a flipflop type of power on/power
off toggle.


Maybe you had it switched on for long enough to partially recharge the
battery???

- Franc Zabkar
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