TenTec
[Top] [All Lists]

Re: [TenTec] Centurion 422b troubleshooting help needed

To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] Centurion 422b troubleshooting help needed
From: "A R" <raf_3@msn.com>
Reply-to: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 29 Feb 2016 15:03:19 -0700
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
   
With installation of the JANTX 2N3055 completed, and three full days of on-air 
operation, the amp is performing beautifully...tube bias problem solved. 
Pre-test of the '88 date-coded JANTX 2N3055: hfe=45, Icbo=0. In-service Tc=38 C 
(max) over 4-hour operating period with Ta=25 C, for a 13 C case temp rise over 
ambient.

Next challenge is properly re-calibrating the metering, which fell victim to 
the former owner's golden screwdriver. Any help wrt performing the metering 
calibration would be apprectiated.

73,

Allen--W7GIF


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

From: A R<mailto:raf_3@msn.com> 

To: Discussion of Ten-Tec Equipment<mailto:tentec@contesting.com> 

Sent: Wednesday, February 24, 2016 12:04 AM

Subject: Re: [TenTec] Centurion 422b troubleshooting help needed



   
Just completed an internal visual inspection of the failed MJ15001 using a 20X 
stereo scope with alternate light sources. Unfortunately my "shade tree" 
failure analysis/forensic lab doesn't include the capability to provide pics of 
the 20X views. 

My conclusions are based on what the 20X visual inspection revealed, and over 
30 years of device/component failure anayses in a former life. In the interest 
of brevity here on the list, I won't include details of what was observed, but 
will offer detailed info via direct email (off-list) to anyone interested.

Suffice to say that I will not be replacing the failed MJ15001 with another 
MJ15001. It is my opinion that the failure was due to a device manufacturing/QC 
issue, and NOT an application-induced overstress of the part.

Since there was no evidence of electrical or thermal overstressing of the 
transistor, I will replace the failed part with a JANTX 2N3055 which, although 
not as robust (spec-wise), at least theoretically it will have been inspected 
and screened to preclude the latent-failure conditions observed in the failed 
MJ15001. Receipt of the JANTX parts is pending. Assuming they pass incoming 
inspection and test, one will get installed in the Centurion, and after a 
reasonable burn-in/shake-down period, I'll update with results.

73,

Allen--W7GIF

 


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

From: A R<mailto:raf_3@msn.com<mailto:raf_3@msn.com>> 

To: Discussion of Ten-Tec 
Equipment<mailto:tentec@contesting.com<mailto:tentec@contesting.com>> 

Sent: Sunday, February 21, 2016 8:49 PM

Subject: Re: [TenTec] Centurion 422b troubleshooting help needed



   
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


TenTec mailing list
TenTec@contesting.com<mailto:TenTec@contesting.com<mailto:TenTec@contesting.com%3Cmailto:TenTec@contesting.com<mailto:TenTec@contesting.com%3Cmailto:TenTec@contesting.com%3Cmailto:TenTec@contesting.com%3Cmailto:TenTec@contesting.com>>>
http://lists.contesting.com/mailman/listinfo/tentec<http://lists.contesting.com/mailman/listinfo/tentec<http://lists.contesting.com/mailman/listinfo/tentec%3Chttp://lists.contesting.com/mailman/listinfo/tentec<http://lists.contesting.com/mailman/listinfo/tentec%3Chttp://lists.contesting.com/mailman/listinfo/tentec%3Chttp://lists.contesting.com/mailman/listinfo/tentec%3Chttp://lists.contesting.com/mailman/listinfo/tentec>>>
_______________________________________________
TenTec mailing list
TenTec@contesting.com<mailto:TenTec@contesting.com<mailto:TenTec@contesting.com%3Cmailto:TenTec@contesting.com>>
http://lists.contesting.com/mailman/listinfo/tentec<http://lists.contesting.com/mailman/listinfo/tentec<http://lists.contesting.com/mailman/listinfo/tentec%3Chttp://lists.contesting.com/mailman/listinfo/tentec>>
_______________________________________________
TenTec mailing list
TenTec@contesting.com<mailto:TenTec@contesting.com>
http://lists.contesting.com/mailman/listinfo/tentec<http://lists.contesting.com/mailman/listinfo/tentec>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec

<Prev in Thread] Current Thread [Next in Thread>