Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Viking Valiant - No grid current




 
The AM Forum
January 21, 2018, 07:57:48 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: 1 ... 4 [5]   Go Down
  Print  
Author Topic: Viking Valiant - No grid current  (Read 5249 times)
0 Members and 2 Guests are viewing this topic.
N1BCG
Member

Offline Offline

Posts: 439


« Reply #100 on: December 28, 2017, 10:50:59 AM »

Yep, something's amiss. You should be able to get a perfect 50Z match with no reactance using expected control settings *.

Check each lug of the "turnstile" cap for resistance to ground. All should be open. Do the same for the mica caps that connect between the bandswitch and the chassis. This will locate shorted caps (most common issue). Be sure to test each of the mica's separately as some are in series.

Open caps can be found by taking a spare cap (all Valiant owners have lots of these) and bridging across each cap. Look for changes that return the control settings to where they should be.

Of course, a capacitor checker can also make fast work of this. I believe the MFJ antenna analyzer has one built in.

* I made a chart of control settings for commonly used frequencies on each band. It shows the knob settings for Drive, Exciter Tuning, Final Plate Tuning, Aux Loading, and Fine Loading. Only minor, if any, adjustments are needed when pre-setting the controls.  

Logged
WZ8J
Member

Offline Offline

Posts: 73


« Reply #101 on: December 28, 2017, 05:04:49 PM »

Yep, something's amiss. You should be able to get a perfect 50Z match with no reactance using expected control settings *.

Check each lug of the "turnstile" cap for resistance to ground. All should be open. Do the same for the mica caps that connect between the bandswitch and the chassis. This will locate shorted caps (most common issue). Be sure to test each of the mica's separately as some are in series.

Open caps can be found by taking a spare cap (all Valiant owners have lots of these) and bridging across each cap. Look for changes that return the control settings to where they should be.

Of course, a capacitor checker can also make fast work of this. I believe the MFJ antenna analyzer has one built in.

* I made a chart of control settings for commonly used frequencies on each band. It shows the knob settings for Drive, Exciter Tuning, Final Plate Tuning, Aux Loading, and Fine Loading. Only minor, if any, adjustments are needed when pre-setting the controls.  


There was continuity between one tab on the turnstile cap and ground. That is the only cap with that condition.
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 1685


Making AM GREAT Again!


« Reply #102 on: December 29, 2017, 06:49:07 PM »

That could completely be within the tolerance of an Mfj device.

--Shane
KD6VXI
Logged
WZ8J
Member

Offline Offline

Posts: 73


« Reply #103 on: December 30, 2017, 05:43:47 PM »

So while I know there is an issue with the turnstile cap, I have learned that the real reason I suddenly couldn't get the plate current to be low enough on 75M was due to my installing the incorrect precision resistor I recently bought for one of the meter shunts. I had somehow managed to install the .404 ohm jobby where the .202 ohm resistor should have been. Now that is fixed and I can again safely load the rig up on 75.
I will address the turnstile cap when I get my latest shipment from Mouser.

Still needing to resolve the HV hum which seems to come from L-43. It physically vibrates. I was able to confirm this by pressing the handle of my solder sucker tool to the side of the case and can feel the vibes coming through. Tried tightening the screws but this had no effect.
 
Logged
WD8KDG
Member

Offline Offline

Posts: 218



« Reply #104 on: December 30, 2017, 05:49:39 PM »

So while I know there is an issue with the turnstile cap, I have learned that the real reason I suddenly couldn't get the plate current to be low enough on 75M was due to my installing the incorrect precision resistor I recently bought for one of the meter shunts. I had somehow managed to install the .404 ohm jobby where the .202 ohm resistor should have been. Now that is fixed and I can again safely load the rig up on 75.
I will address the turnstile cap when I get my latest shipment from Mouser.

Still needing to resolve the HV hum which seems to come from L-43. It physically vibrates. I was able to confirm this by pressing the handle of my solder sucker tool to the side of the case and can feel the vibes coming through. Tried tightening the screws but this had no effect.
 

L-43...............I've never seen one, but:

If there are bell ends.........remove them. There is a thimble with the windings that is on the iron lamination. A wooden wedge might do the trick??

Craig
Logged

Ham radio is now like the surprise in a box of "Cracker-Jacks". There is a new source of RFI every day.
Pages: 1 ... 4 [5]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.047 seconds with 18 queries.