[hpsdr] LPU assembly, -12v problem

[AA8K73 GMail]

I wired my LPU and the -12V supply wouldn't work.
Went through and measured each resistor again (I
had measured them before installation).  The LT1931
U4 pin 1 had some positive voltage on it.  I examined
each part with a magnifying glass for a correct
solder connection.  I poked around the -12V circuit
with a scope.  Finally convinced that I had a bad
LT1931, just to be sure, I re-soldered every
connection in the -12V portion of the LPU.  I
plugged it in and it has been running fine since.


Mike - AA8K


On 11/01/2010 12:27 PM, Richard Landsman wrote:
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> Just finished assembling my LPU in preparation for firing up the boards
> set I purchased from John.  Everything looks good, expect for the -12v
> supply.  I have a Janus board I'd like to try, so I can't just disable
> this with the jumper. Voltages on LT1931 1:11.78, 2:12.19, 3:5, 4:13.6,
> 5:13.65.  I expected to see a -12v on pin 1, but see +12 instead.  V at
> pin 12 of J1 is 65mv.  Checked polarity of C20 and D1.  Any ideas would
> be appreciated.
>
> Rich
>

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