Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Ameritron Amp Problem  (Read 2061 times)
N3CRP
Member

Posts: 5




Ignore
« on: November 09, 2012, 07:09:26 AM »

When I turn the amp on, the plate current goes to 100 ma and the grid current meter goes negative. I get the same results with all the cables disconnected. I'm driving it with an FT-847 transceiver running about 100 watts. It has always run well until recently. Any clues to what the problem could be?
Logged
AD4U
Member

Posts: 2153




Ignore
« Reply #1 on: November 09, 2012, 07:28:30 AM »

Which amp?Huh?  Bad tube?

Dick  AD4U
Logged
N4ATS
Member

Posts: 799




Ignore
« Reply #2 on: November 09, 2012, 08:24:17 AM »

Replace D-16 right behind the meter on the HV board. (1N4001) use a 1N4006 if you have one
Logged
W1QJ
Member

Posts: 1439




Ignore
« Reply #3 on: November 09, 2012, 08:45:31 AM »

Replace D-16 right behind the meter on the HV board. (1N4001) use a 1N4006 if you have one

I think he has one or more bad tubes G-F short.  D-16 makes grid track plate...No?
Logged
N4ATS
Member

Posts: 799




Ignore
« Reply #4 on: November 09, 2012, 09:08:28 AM »

I have seen this a lot , when that diode goes bad the needle does go negative... However what made it go was probably a arc or who knows. Its a simple 1 minute test to see if it is bad or not which can save him time.

I had one last week with a shorted diode that went bonkers on 20 meters at a certain load position. Have NO clue why but it did... The tubes were good , I put them in my shop queen and it loaded up fine. Then replaced the shorted diode , put the tubes back in and it loaded just fine.

Logged
NO2A
Member

Posts: 754




Ignore
« Reply #5 on: November 09, 2012, 08:58:32 PM »

I suspect if you remove the tube and power up the amp you won`t see any negative grid current. This would indicate a tube short. Like Lou said,if D-16 goes bad both meters track each other(act like the same meter movement). Hopefully if it did arc it didn`t take out any components.
Logged
K4DPK
Member

Posts: 1077


WWW

Ignore
« Reply #6 on: November 15, 2012, 08:19:39 PM »

Grid-cathode short.

Phil C. Sr.
k4dpk
Logged
K4DPK
Member

Posts: 1077


WWW

Ignore
« Reply #7 on: November 15, 2012, 08:26:50 PM »

Just thinking....

I think most of the time (with a 3-500 amp) when these symptoms appear, it's a shorted tube, but I recall a Drake amp I repaired once that was different.  It ran a single 3-500, and one of the ceramic discs that bypassed the filament transformer leads between the choke and the transformer had shorted.

Of course the result was the same, but it took a few minutes longer to find it.

Phil C. Sr.
k4dpk
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!