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Title: WHY LOW GRID CURRENT ON 160 ONLY?.. Post by: ve6pg on January 15, 2006, 11:16:38 PM ..HI FROM TIM..MY VIKING 2 HAS TONS OF RF OUT,AND GRID CURRENT ON ALL BANDS,EXCEPT 160...BEST I CAN DO ON 160 IS ABT 4 MILS,AND GET ABT 75 WATTS OUTPUT...PLATE CURRENT IS BEST AT 200MILS..EVEN A DUMMY LOAD,NO DIFFERENCE ON THE OUT POOT....IDEAS?...SK..
Title: Re: WHY LOW GRID CURRENT ON 160 ONLY?.. Post by: W3SLK on January 16, 2006, 08:52:36 AM Tim, I don't have the schematic in front of me but I would check the driver section of the rig. Sounds like a component changed value that isn't too significant at higher freq.
Title: Re: WHY LOW GRID CURRENT ON 160 ONLY?.. Post by: Jim, W5JO on January 16, 2006, 10:01:43 AM Tim, are meter reading M1 and M2 OK?
Title: Re: WHY LOW GRID CURRENT ON 160 ONLY?.. Post by: Warren on January 16, 2006, 10:16:04 AM Tim,
I had a similar problem with a DX-100. Turned out to be the coil in between the driver output circuit and the PA grid. The DX-100 switches in extra coils as you go to lower frequency bands. The 160 coil had shorted turns and the grid drive was low. It can be tricky to diagnose since the coil will still read good on an ohmmeter. 73 & GL Warren K2ORS/WD2XGJ Title: Re: WHY LOW GRID CURRENT ON 160 ONLY?.. Post by: W2JBL on January 16, 2006, 09:57:58 PM replace the screen resistors in the oscillator and first multiplier stages (they tend to open up), and swap the 6AH6 to a 6AK6. you should have more than enough drive on all bands after that. same for the 122 VFO- replace all the resistors. they don't age well.
Title: Re: WHY LOW GRID CURRENT ON 160 ONLY?.. Post by: WA1GFZ on January 18, 2006, 07:37:26 PM Good thought Chris. I did the VFO but never the osc / driver screen resistors. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
My V2 has the same problem on 160. Changing tubes did nothing to help. I have not looked at the voltages since '83. when i went PDM might be time to check again. BTW swapped out the modulators for the first time amd found no change so put the old 6DQ5 back in. gfz |