[hpsdr] Penelope Power Problem

[Scott Cowling]

Hi Bill,

Yes, you are correct.

John, you might try giving the DAC and PA area (basically between U7 
and T2) a quick visual going over. You could have a solder connection 
that broke loose either from handling or from thermal cycling. It is 
a long shot, but might be an easy fix if it is the problem.

73,
Scotty WA2DFI


At 17:14 2010-11-22 -0600, Bill Tracey wrote:
>***** High Performance Software Defined Radio Discussion List *****
>
>I think the LED power meter on Penny actually measures the output 
>power, so it would read lower if the OPA2674 is not putting out full power.
>
>Regards,
>
>Bill (kd5tfd)
>
>At 02:48 PM 11/22/2010, John Petrich wrote:
>>***** High Performance Software Defined Radio Discussion List *****
>>
>>Sorry to bother people, but Penelope suddenly dropped power output 
>>from the nominal 500mW to about 220mW.  This happened following a 
>>demonstration at the local ham club meeting.  Additional 
>>observations are that only 4 of the 5 LED's will light with maximum 
>>drive, and at the 220mW level, Penelope outputs picket fence IMD 
>>spurs every 2 KHz @-30dBc and down.  Reducing the drive through the 
>>PA Settings, Gain by Band menu, from "38" to"39" maintains the same 
>>nominal 220mW output, but the IMD spurs disappear.
>>
>>Does anyone have a diagnosis?
>>
>>The 1/2 power output and IMD observation suggests to me that part 
>>of the output amplifier, OPA26741 IC, has failed.  I cannot explain 
>>the fact that only 4, instead of 5, LEDs will light with maximum drive.
>>
>>Any suggestions are appreciated.
>>
>>Regards,
>>John Petrich, W7FU
>
>
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