[Central-Electronics] 6AG7 problem

[Jim Candela]

 Nice to see some posts here.
On the 20A, remember the 6AL5 has one section used as the bias rectifier. If that tube does not lite, you get the 6AG7 Chernobyl effect.
Many of the old 6AL5 sockets and tubes fail to make the filament connection solid.
This is a common issue with these rigs.
JimWd5JKO

    On Sunday, November 15, 2020, 1:31:43 PM CST, Bob Heil <bob at heilsound.com> wrote:  
 
 I am always thrilled to see 12 watts from any of our 20A transmitters!

Dr. Bob Heil, K9EID

> On Nov 15, 2020, at 12:57 PM, Colin Lamb <k7fm at teleport.com> wrote:
> 
> Hello:
> 
> I own a Central Electronics 20A.  I only had 12 watts output.  I checked the 6AG7 with my TV-7/U tester and both seemed fine.  Everything else seemed good.  I was trying it on 80 meters.  But I changed one of the tubes and a new tube gave my 20 watts output.  Then, all was fine.  I tuned it up and suddenly the rectifier was red hot.  I see the 6AG7 is connected directly to the high voltage supply.  There is 300 vdc on the plates and screen.  This is the maximum voltage that can be applied.  My line voltage is 121.5 volts.  I took the 20A apart and one of the GE 6AG7 had a shorted screen.  I threw it away.  Now, a second GE 6AG7 tube does exactly the same thing.  I have to take the rig apart and see if another 6AG7 has a shorted screen.  I have 2 IRCA 6AG7 tubes.  But I have used the Central Electronics for 50 years and never had that problem.  
> 
> Any suggestions?
> 
> Colin  K7FM
> ______________________________________________________________
> Central-Electronics mailing list
> Home: http://mailman.qth.net/mailman/listinfo/central-electronics
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Central-Electronics at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

______________________________________________________________
Central-Electronics mailing list
Home: http://mailman.qth.net/mailman/listinfo/central-electronics
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:Central-Electronics at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html