Check this out. It sounds like this guy had the same problems as you are
having.
http://www.eham.net/reviews/detail/113
73, Clint, VE3CMQ (formerly VE6CMM)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of
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Sent: November 21, 2017 11:00 AM
To: tentec@contesting.com
Subject: TenTec Digest, Vol 179, Issue 20
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Today's Topics:
1. Centurion Problem (Michael Marx)
2. Centurion Bias Transistor Follow on post (Michael Marx)
3. Re: Centurion Bias Transistor Follow on post (James Duffer)
4. Re: Centurion Bias Transistor Follow on post (Lee)
5. Re: Centurion Bias Transistor Follow on post (w3ka@lycos.com)
----------------------------------------------------------------------
Message: 1
Date: Mon, 20 Nov 2017 11:47:08 -0600
From: Michael Marx <sndtubes@vacuumtubes.com>
To: TenTec@contesting.com
Subject: [TenTec] Centurion Problem
Message-ID: <D6A233D0-59DF-4229-A537-0CADE2424698@vacuumtubes.com>
Content-Type: text/plain; charset=us-ascii
Hi Guys,
I have a Centurion that experienced some kind of arcing event which resulted
in one of the traces on the Filter/Rectifier board that connects to the
secondary of the transformer to actually vaporize. I bridged the trace,
replaced the capacitors and checked the diodes. After repairing /
rebuilding the board, I reinstalled it and now have normal B plus. HOWEVER,
I have 200 mA of standby plate current. This suggests the bias transistor
is blown and I have had this problem in the past. Unfortunately, I replaced
the bias transistor and still have 200 mA of standby plate current. My
question is: Do any of you have an any idea of what to check besides the
bias transistor. Or, is there some common cause for the transistor to fail?
I bought 5 of them from Mouser and hesitate to keep replacing them until I
know what is causing the failure. The transistors I bought are IDENTICAL to
the transistor I bought from Ten Tec the last time it failed.
thanks
73
Mike WB0SND
Michael Marx
sndtubes@vacuumtubes.com
636-939-9190
SND Tube Sales
105 N. Division St.
Bonne Terre, MO 63628
------------------------------
Message: 2
Date: Mon, 20 Nov 2017 12:09:53 -0600
From: Michael Marx <sndtubes@vacuumtubes.com>
To: TenTec@contesting.com
Cc: TenTec@yahoogroups.com
Subject: [TenTec] Centurion Bias Transistor Follow on post
Message-ID: <3E22D63E-1C3C-4DFA-BD2A-6F487CA9A4C8@vacuumtubes.com>
Content-Type: text/plain; charset=utf-8
Guys,
I just posted a message about my Centurion with a bias problem. As I stated
I replaced the bias transistor which did not fix the problem. Here is
something interesting that I don?t understand. I bought 5 of them from
Mouser. When I measure the transistor junctions with my Fluke 87 meter in
the diode function, one junction seems normal as it measures .5 V in one
direction and open in the other. Normal, right? Now the other junction
measures open in both directions. It also measures open in ohmmeter mode.
Could I have bought 5 bad transistors? Is that even possible? What am I
doing wrong in testing these transistors? They are just an NPN bipolar
transistor, right? FYI it is an MJ15001G by ON. This is exactly what Ten
Tec sent a few years ago when I had to replace the transistor.
Very confused.
73
Mike WB0SND
Michael Marx
sndtubes@vacuumtubes.com
636-939-9190
SND Tube Sales
105 N. Division St.
Bonne Terre, MO 63628
------------------------------
Message: 3
Date: Mon, 20 Nov 2017 18:18:50 +0000
From: James Duffer <dufferjames@hotmail.com>
To: Michael Marx <sndtubes@vacuumtubes.com>, "TenTec@contesting.com"
<TenTec@contesting.com>
Cc: "TenTec@yahoogroups.com" <TenTec@yahoogroups.com>
Subject: Re: [TenTec] Centurion Bias Transistor Follow on post
Message-ID:
<BY1PR0301MB08855352459C898577A3120AB9220@BY1PR0301MB0885.namprd03.prod.outl
ook.com>
Content-Type: text/plain; charset="Windows-1252"
Isn't it in the TO-204-2 package, where the case is the "drain"?
________________________________
From: TenTec <tentec-bounces@contesting.com> on behalf of Michael Marx
<sndtubes@vacuumtubes.com>
Sent: Monday, November 20, 2017 12:09 PM
To: TenTec@contesting.com
Cc: TenTec@yahoogroups.com
Subject: [TenTec] Centurion Bias Transistor Follow on post
Guys,
I just posted a message about my Centurion with a bias problem. As I stated
I replaced the bias transistor which did not fix the problem. Here is
something interesting that I don?t understand. I bought 5 of them from
Mouser. When I measure the transistor junctions with my Fluke 87 meter in
the diode function, one junction seems normal as it measures .5 V in one
direction and open in the other. Normal, right? Now the other junction
measures open in both directions. It also measures open in ohmmeter mode.
Could I have bought 5 bad transistors? Is that even possible? What am I
doing wrong in testing these transistors? They are just an NPN bipolar
transistor, right? FYI it is an MJ15001G by ON. This is exactly what Ten
Tec sent a few years ago when I had to replace the transistor.
Very confused.
73
Mike WB0SND
Michael Marx
sndtubes@vacuumtubes.com
636-939-9190
SND Tube Sales
105 N. Division St.
Bonne Terre, MO 63628
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------------------------------
Message: 4
Date: Mon, 20 Nov 2017 18:59:56 +0000
From: Lee <lee@wa3fiy.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Subject: Re: [TenTec] Centurion Bias Transistor Follow on post
Message-ID: <em1a220d87-dece-490e-92f5-24fa4476ba01@owner-pc>
Content-Type: text/plain; format=flowed; charset=utf-8
Hi Mike,
You are probably doing this but I will ask just to be sure. Are you using
the BASE as the common test point and testing EMITTER and COLLECTOR to base.
In a NPN transistor the BASE - EMITTER junction is one diode where the BASE
is the anode and EMITTER the cathode. The BASE
- COLLECTOR junction is the other diode where the BASE is the anode and
COLLECTOR the cathode. Testing the EMITTER - COLLECTOR leads will show
open in both directions when the BASE is open.
73,
-Lee-
WA3FIY
------ Original Message ------
From: "Michael Marx" <sndtubes@vacuumtubes.com>
To: TenTec@contesting.com
Cc: TenTec@yahoogroups.com
Sent: 11/20/2017 1:09:53 PM
Subject: [TenTec] Centurion Bias Transistor Follow on post
>Guys,
>
>I just posted a message about my Centurion with a bias problem. As I
>stated I replaced the bias transistor which did not fix the problem.
>Here is something interesting that I don?t understand. I bought 5 of
>them from Mouser. When I measure the transistor junctions with my
>Fluke 87 meter in the diode function, one junction seems normal as it
>measures .5 V in one direction and open in the other. Normal, right?
>Now the other junction measures open in both directions. It also
>measures open in ohmmeter mode. Could I have bought 5 bad transistors?
> Is that even possible? What am I doing wrong in testing these
>transistors? They are just an NPN bipolar transistor, right? FYI it
>is an MJ15001G by ON. This is exactly what Ten Tec sent a few years
>ago when I had to replace the transistor.
>
>Very confused.
>
>73
>Mike WB0SND
>
>
>Michael Marx
>sndtubes@vacuumtubes.com
>636-939-9190
>
>SND Tube Sales
>105 N. Division St.
>Bonne Terre, MO 63628
>
>
>
>
>_______________________________________________
>TenTec mailing list
>TenTec@contesting.com
>http://lists.contesting.com/mailman/listinfo/tentec
------------------------------
Message: 5
Date: Mon, 20 Nov 2017 19:28:50 +0000
From: w3ka@lycos.com
To: Discussion of Ten-Tec Equipment <tentec@contesting.com>
Subject: Re: [TenTec] Centurion Bias Transistor Follow on post
Message-ID: <7d1474c3c4e344babe2382575ddc34ff@lycos.com>
Content-Type: text/plain; charset=US-ASCII; format=flowed
Hi Mike.. When troubleshooting the same problem on a Ten Tec Titan 425,
excess idle current, the fix was an open diode, in the B- bias line to the
tubes. I am not familiar with the centurion bias circuit, but check to see
if TT also used a diode in series with the B- line causing a loss of bias to
the tubes. 73, Jim
On 2017-11-20 18:09, Michael Marx wrote:
> Guys,
>
> I just posted a message about my Centurion with a bias problem. As I
> stated I replaced the bias transistor which did not fix the problem.
> Here is something interesting that I don't understand. I bought 5 of
> them from Mouser. When I measure the transistor junctions with my
> Fluke 87 meter in the diode function, one junction seems normal as it
> measures .5 V in one direction and open in the other. Normal, right?
> Now the other junction measures open in both directions. It also
> measures open in ohmmeter mode. Could I have bought 5 bad transistors?
> Is that even possible? What am I doing wrong in testing these
> transistors? They are just an NPN bipolar transistor, right? FYI it
> is an MJ15001G by ON. This is exactly what Ten Tec sent a few years
> ago when I had to replace the transistor.
>
> Very confused.
>
> 73
> Mike WB0SND
>
> Michael Marx
> sndtubes@vacuumtubes.com
> 636-939-9190
>
> SND Tube Sales
> 105 N. Division St.
> Bonne Terre, MO 63628
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
------------------------------
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