Re: Help reclaiming the magic smoke that came out of my 50W PA #help #magicsmoke #troubleshooting


Charles Johnson
 

To all,

After some testing - I measured R5 with the amp powered off as I turned the trim pit and then tried the bias adjustment procedure again (QCX+ Practice Mode on) - I have come to the conclusion that R5 needs to be replaced. First, are there any other parts I should replace just for good measure? Second, what is the make/model for R5? (the Digi-Key/Mouser/etc part # would really be appreciated!).

Also, while Hans lists 85mA in the build instruction guide, on my first bias adjustment attempt, I was measuring 93mA, and in another thread, someone mentions a bias value well in excess of 100mA. Is there a common window in which the bias values usually fall?

Charles Johnson
KF4AYT

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