[TenTec] Centurian amp...more info..and more questions

[A R]

Go back into the archives to Feb 21, 2016 for Centurion 422b troubleshooting help needed". My Centurion showed 140ma plate current when unkeyed in standby mode. Found the bias xistor Q1 on the FILAMENT-AC BOARD to have failed. Q1 in my amp was a MJ15001 from "ON" (mfr) date coded 0318. Failuer analysis on the failed Q1 revealed serious, gross conditions on the die that should have been revealed during pre-close inspection of the xistor. Die was damaged extensively, but it took many ours of operation before the die failed catasprophically.

 

If the failure symptoms I described in my 2/21 post mirror those that you've encountered, I'd look closely at Q1. Is it a MJ15001? If so, mho mfg it, and what's the date code?

 

I replaced Q1 in my Centurion with a JANTX 2N3055. It's been performing beautifully since late Feb, and runs very cool...and NO plate or grid current when in STANDBY mode. Replacing Q1 is a real PITA. Don't lose the tiny nylon shouldered washers for the Q1 mounting screws, or the (hidden) steel washer that's located in the center of the board between the two assemblies that have to be separated to access/replace Q1.

 

Good luck, and best 73...

Allen--W7GIF


----- Original Message ----- 

From: kr2q at optimum.net<mailto:kr2q at optimum.net> 

To: tentec at contesting.com<mailto:tentec at contesting.com> 

Sent: Thursday, May 26, 2016 4:16 PM

Subject: [TenTec] Centurian amp...more info..and more questions



Hi again

I just reread the QST review article.  I now note that they cited plate idle current when the
amp was in OPERATE but not keyed.

My amp shows idle current while in STANDBY.

Does that lead to any clues as to what might be "wrong?"

Also, SN is 09A 10027.  What year is that from?

Thanks again,
de Doug KR2Q
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