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THE AM BULLETIN BOARD => Technical Forum => Topic started by: ve6pg on August 31, 2005, 04:37:22 PM



Title: LOW OUTPUT ON 160..VIKING2
Post by: ve6pg on August 31, 2005, 04:37:22 PM
OK..FINISHED THE NC300,AND LOADED UP MY VIKING2 ON 160 LAST NIGHT..CANT GET MORE THAN 200MILS ON TX,AND GRID DRIVE LOW.ALL IS FB ON 75-10.OUTPUT ON 160 ABOUT 65WATTS MAX INTO A DUMMY LOAD. ANY IDEAS AS TO THE POSSIBLE FAULT HERE?..TIM...SK..


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: WA1HZK on August 31, 2005, 05:35:55 PM
How's your Grid drive on 160?


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: Pete, WA2CWA on August 31, 2005, 05:41:13 PM
crystal or VFO operation?
160 meter front panel switch in or out and/or, do you know it's working properly?

Both of my Viking II's had two dips when cranking the plate tuning for 160. The correct one was the one at lowered numbered scale.


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: ve6pg on August 31, 2005, 06:51:19 PM
...vfo..(122). 160 switch in,grid drive about,4mils...all else ok on other bands..tank is tuned very low fer dip,just above zero. not quite 200mils on the plate in tx(CW). "antenna" loading at "6". this is into a dummy load,flat swr...thanks..tim..sk..


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: Jim, W5JO on August 31, 2005, 07:13:50 PM
Tim are you tuned to the wrong frequency with either the oscillator or driver caps?  Is the VFO on the wrong side of the frequency dial? 


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: ve6pg on September 01, 2005, 07:38:03 AM
..NO JIM,ALL IS OK,AS I'VE BEEN USING THE RIG FOR 20YRS..'WAS LAST ON 160 ABOUT..2 MONTHS AGO,AND ALL WAS FB..JUST THE OTHER NIGHT THO,AS I MENTIONED,IT WAS (AND STILL IS) LOW. I HAVE GOBS OF GRID CURRENT ON ALL BANDS,EXCEPT 160.HENSE,THE OUTPUT IS MAYBE 65 WATTS. I JUST CHECKED IT AGAIN,AND SAME PROBLEM. I HAVE A QSO MOST MORNING ON 3725 AM,AND JUST TUNED UP FER THAT...AM CARRIER-90 WATTS,105 ON CW. ..THE MYSTERY DEEPENS..  TIM...SK..(http://)


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: Jim, W5JO on September 01, 2005, 09:27:07 AM
Well Tim, what about the integerity of the 160" In and Out" switch?  Could the contacts be burned/corroded  or the coil not swiltching in.  The book says the Coarse coupling should not be advanced past 6.  Could one or more of these fixed caps be bad.  Seems as if that is where it is leading.


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: ve6pg on September 01, 2005, 10:27:04 AM
...JIM..THIS IS KINDA WHAT I'M THINKING...ELECTRICALLY THE CONTACTS SHOULD BE FINE,AS I DID A MAJOR OVERHAUL ABT 6 MONTHS AGO. I WENT ALL OVER THE RIG,REPLACING ALOT OF CAPS,RESISTORS,SOME AUDIO MODS,ETC. THERE WASNT A PROBLEM WITH THOSE FIXED MICAS,SO I DIDNT DO ANYTHING WITH THEM. NOT OFTEN THAT THEY GIVE YOU PROBLEMS. I HAVENT PULLED THE RIG DOWN AS YET,KIND OF CRAMPED IN THE SHACK,SO I WANTED A "PLAN OF ATTACK",BEFORE I DISCONNECTED EVERYTHING,SO AS TO BE ABLE TO MINIMIZE THE DISASTER EFFECT OF BITS/PIECES ALL OVER THE PLACE..HI!. I'LL GO BACK AND LOOK AT THE DRAWINGS,AND TRY TO DETERMINE WHICH CAP(s) I MIGHT BE LOOKING AT,WHICH" NUMBER" THEY MIGHT BE,AND THEIR VALUES....TIM...SK..


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: Jim, W5JO on September 01, 2005, 11:05:50 AM
Tim if memory serves, those caps are .0003 (5 of them)  and one .00015.  As I recall, they are low voltage, probably 600 volts, molded micas.  One or more could have wicked moisture over the years.


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: WA1GFZ on September 01, 2005, 11:59:16 AM
Hang 1000 pf across the output PL259 and see if anything happens
It should drop the plate current.
My V2 plate tuning is almost the same place on 3885 and 1945 but remember an extra inductor is switched in on 160.
Your loading caps may be open and you may have the final ending up on 75 M acting like a doubler. A clue would be look at the swr connected to a 75 m ant. Or look at the cw signal with a scope to check the frequency.
check your screen bypass cap too.


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: Tom WA3KLR on September 01, 2005, 08:03:50 PM
Hi Tim,

I have a Viking II on 160 meters AM. 
I use the Model 122 external VFO.  VFO band sw. at "160, 80, 40". Freq = 1.885
Crystal position set at 0.
Antenna load is near 50 Ohms. 
Plate current is loaded to 225 ma.
Grid current drive is set to one minor division below the red mark (7.5 ma.)  The red mark is at 8 ma., max. grid spec.

The settings are:

Oscillator 25
Buffer 59
Drive ~ 5.6
Final Tune 14
Coupling 2
Fine coupling 31

Good luck.


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: Paul, K2ORC on September 02, 2005, 11:00:46 AM
Hi Tim.  I use Viking I and II on 160 meters with VF-1 and VG-122 vfos respectively. 

A thought, but have you checked to make sure that lovely string loop that passes through the chassis to engage the coil via the 160m in/out switch is intact?  I had to replace the string on the II once.  Not a fun job.   Pete CWA's observation about the two dips on final tune -- one being a false -- is also worth pursuing further.  That anomaly is noted in the owner's manual, I believe.


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: ve6pg on September 02, 2005, 11:31:14 AM
...well, the string assy is ok. as far as grid drive,the best i can get is something like,4-5mils,usually 4. on a dummy,i set the coupling to 6. this is far diiferent than all the other bands,as i've stated. i'm going to have to check the mica caps,as they may be the problem. as i've stated earlier,all controls,band switching,160 in/out,tank,are all set to proper settings,but output is low. it has to be in the switching assy,with those caps. at least i found this out,before the 160 winter season starts. i've been doing tests on 1885  with ve3ajm al, and last evening mike,ve3fgu. prop and noise have been ok. i'm attempting to get more of our group here in ve3 to get on 160. ..the search continues..sk..


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: Paul, K2ORC on September 09, 2005, 05:40:20 PM
Tim, I wonder whether you've figured out why the low grid and plate current on 160 only?


Title: Re: LOW OUTPUT ON 160..VIKING2
Post by: ve6pg on September 09, 2005, 07:21:23 PM
..nothing as yet,i'm a bit perplexed...caps appear ok,all contacts fb...i'm overlooking something,somewhere..i'll keep looking...!..sk..
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