[hpsdr] LPU assembly, -12v problem

[Richard Landsman]

Thanks Mike and Scotty, I found the problem.  Even though I had resoldered
everything twice, Pin 2 was not grounded.  Refluxed and hit it again and
-12v is where it should be.  I should have realized that Pin 2 was Gnd, but
got confused between the data sheet and the schematic.  Looking at the
schematic quickly, without paying attention to pin numbers, it looks like
Pin 2 is the other side of the 10K pull-up on the disable line.  Next stop,
Atlas and Ozy checkout.

On Mon, Nov 1, 2010 at 1:48 PM, AA8K73 GMail <aa8k73 at gmail.com> wrote:

>
> 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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