Duane, Andy, and Carter:
Wow. Just confirmed that the TO-3 bias transistor (MJ15001) in my 422b is
shorted collector-to-emitter. Admittedly, 4 failures isn't a huge sample, but
it sure suggests that there's either a quality problem with the MJ15001's, or
the circuit (application) is overstressing their spec'd characteristics/limits.
Did you all re[place the faied transistors with MJ15001's, or some other
transistor? My 422 manual calls out a 2N3055, which is a "15A, 60V, 115W"
device, compared with the MJ15001's "20A, 140V, 250W" rating. Without knowing
the root cause of Q1 failures, I'm tempted to "socketize" Q1. At least
replacing Q1 again (if needed) wouldn't be quite the PITA (and board-stressing)
as it is with a soldered-in Q1. How much failure-free time on your amps since
replacement of Q1? Thanks for the feedback and good info!
73,
Allen--W7GIF
----- Original Message -----
From: Duane Calvin<mailto:ac5aa1@gmail.com>
To: 'Discussion of Ten-Tec Equipment'<mailto:tentec@contesting.com>
Sent: Sunday, February 21, 2016 6:14 PM
Subject: Re: [TenTec] Centurion 422b troubleshooting help needed
Bias transistor? I had one go out on my Centurion when it was only a couple
hours old.
73, Duane
Duane Calvin, AC5AA
Austin, Texas
ac5aa@ac5aa.com<mailto:ac5aa@ac5aa.com>
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