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50W PA R5 adjustment... what do you find?


Brian N7BKV
 

Pages 66 of amp manual version 1.00p  explains how the R5 is adjusted (remember first, practice mode and straight key mode).
I found the rise begins off full CCW position to be at about 6 to 8 mA.  About 30 degree turn of R5.
Amps works fine with that.
But what are you finding when doing that adjustment?  The random figure in the manual was 85mA. 

Brian N.
N7BKV


g4edg
 

Mine was 135mA

Steve G4EDG


Don Lee
 

Hi Brian -

I had a similar issue.  It turned out that I had not properly burned off the enamel on one of the leads of the trifilar transformer.  I performed the continuity checks again to determine which lead was the problem.  Then I just resoldered both ends holding the iron tip at the joint for 10-15 seconds - I did not remove it.

Hope your issue is as easy as mine!
--
73,
Don WB4FAS


Brian N7BKV
 

Thanks Don.  I check continuity and no issues there.  I am more curious if the 6 to 8 mA on tune up is within common experience of 50W PA builders.  What was the reading you got on tuneup of R5?  Before and after the trifilar repair?

73
Brian N
N7BKV


On Sat, Oct 17, 2020 at 07:03 AM, Don Lee wrote:
I had a similar issue.  It turned out that I had not properly burned off the enamel on one of the leads of the trifilar transformer.  I performed the continuity checks again to determine which lead was the problem.  Then I just resoldered both ends holding the iron tip at the joint for 10-15 seconds - I did not remove it.

Hope your issue is as easy as mine!
--
73,
Don WB4FAS


Don Lee
 

If memory serves, it was around 7ma before, then 75ma after.  Sorry I couldn't be of much use to you.  Good luck - I hope you solve it!
--
73,
Don WB4FAS


Ronald Taylor
 

Brian, 6-8 mA current draw during tune up is not correct. It should be 60-80 mA typically. You indicate the amp works fine. If that's the case, you might want to check your ammeter on a known load. I don't think it's reading correctly. What does it indicate for current flow when actually amplifying RF?

Ron