Finally got the PLO's working.

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n7oq
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Joined: Sat Apr 28, 2018 6:49 pm

Finally got the PLO's working.

Post by n7oq » Mon Feb 10, 2014 7:04 am

I tested my PLO's today and I set up for the PLO  power tests and when I loaded the software is said the sweep would show the final filter and all I got was a lot of noise. I swapped out PLO 1 with PLO 3 and it started to work. But One of the outputs was half the what the other one was. I found I forgot to solder one side of a capacitor on the amp input. That fixed that problem. I troubleshot the bad PLO and found one of the ERA-33's was shorted so I replaced it and that fixed that problem. The bad output was a PLL lock problem, the control voltage out of LMX2326 pin2 looked like a ugly sine wave instead of a clean DC voltage. I was about to replace the LMX2326 but did more checks and finally found that U3 LT1677 output pin6 to the ROS2150  has a 470 ohm resistor and I had put in a 470K ohm resistor, I replaced it and bingo it now works. Not sure how I did that sense I built both PLO1's at the same time and one had the right resistor and the over one was the wrong one. I seem to always make simple dumb mistakes, but hay if it worked first time every time you would,never get to practice your troubleshooting skills. 
Tomorrow I will finish my power calculations but a quick check showed all my outputs were the same now and it look good. Then I will put everything together and see it this thing will actually work. Bill

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