[hpsdr] LPU assembly, -12v problem

[Scott Cowling]

Hi Rich,

Check the solder joint at pin 2 of the LT1391. It is the ground pin. 
Since it is at +12V, you are not likely to get the regulator to function.

73,
Scotty WA2DFI


At 16:48 2010-11-01 -0400, AA8K73 GMail wrote:
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>
>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:
>>***** High Performance Software Defined Radio Discussion List *****
>>
>>
>>
>>
>>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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