[hpsdr] LPU Photo

[Scott Cowling]

Hi Greg,

Check capacitor C23 for proper orientation and value (100uF 10V 
tantalum).  U2 (+5V regulator) tends to oscillate with only 10uF of 
ceramic bulk capacitance at its output.  You might check C11 on the 
+12V regulator also, but it would not give you as much noise on 
Mercury as the +5V one will if it oscillates.

There is a picture on the Wiki here:

http://openhpsdr.org/wiki/images/8/8f/LPU_BOT_sm.JPG

It is of the rev A PCB. Even though the artwork is different that the 
rev B production PCBs, you can see the mods that include the larger 
tantalum caps at C3, C7 and C11.  Rev B added 100uF tantalum caps C22 
and C23 in parallel with C3 and C7, respectively and changed C3 to 
47uF tantalum.

73,
Scotty WA2DFI


At 11:46 PM 3/21/2010 -0400, Greg wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>Greetings to the List
>
>Would someone plse send me a hi-res photo of the bottom view of  a
>working LPU unit.
>
>I am having very high noise coming out of my unit, though the voltages
>all look good. I may have one or more parts improperly oriented. If I
>use a computer supply in place of the LPU, Mercury works fine. With
>the LPU the noise is off the scale and kills everything. The noise is
>heard even before PowerSDR is stated up.
>
>I have all the latest firm ware installed and JP1 is jumpered.
>
>Thanks to all.  Great project and my thanks to all who have worked so
>hard to make this happen.
>
>73
>
>Greg Danylchenko/VE3YTZ
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