High plate current with Viking II.

[KC2TAU]

I've been attempting to resurrect a Viking II that is at my university's club station and could use some advice as to how to proceed. I have buffer, oscillator, grid and plate current but the resting plate current without any drive is far too high (~220ma). The interesting issue is that the plate current does not respond to changing the coupling circuit. Adjusting either loading controls or the final adjustment does nothing to the plate current. The buffer, oscillator and drive controls are responsive, however. Adjusting the clamper tube with the variable resistor R30 does not change the resting plate current. Any ideas would be appreciated.

[KA2DZT]

Without any DRIVE??  That's your problem.  You need drive.

Plate tuning and loading won't respond without grid drive.

Fred

[KA2DZT]

Oh!  Maybe I misread your question.  Seems that you're checking the clamp circuit.  Clamp circuits that I've built pull down the screen voltage on the PA.  Check the screen resistor for the PA.  Check the clamp tube maybe it's weak or dead.

Fred

[WQ9E]

Check your bias supply output voltage.  If you haven't changed the filter caps in the bias supply I would do so before further testing.

[WBear2GCR]

Make sure there is a connection through the pi-network to the load and that the load is connected...

Btw, did you get the receiver to work??

                       _-_-bear

[KC2TAU]

I'm going to most likely buy a spare (working) crystal filter module and then play with the other one to both better understand it as well as hopefully fix it.

These are great suggestions, I'm probably going to just end up bringing the TX home so that I can dedicate more time and so I'll let you know what I find. Keep the suggestions coming and I'll report back on what I see.

[w4bfs]

Check your bias supply output voltage.  If you haven't changed the filter caps in the bias supply I would do so before further testing.

Rodger is spot on here, especially in a VII .... since the lv xfmr is not separately fused, it is VERY vulnerable to leaky power supply electros ...ignore this at your peril ...73...beefus 

[w1vtp]

The V2 uses fixed bias and a clamper tube.  You need to make sure both are working.  One of the first things the manual has the operator do when receiving a new V2 is to make sure the resting current is in spec.   Check both the negative bias and the clamper to be sure both are working. The manual has you dong this first and then you can address problems with the drive to the finals, dipping of plate current and coupling to antenna.

When you are at the point of tuning the finals make sure you have ~ 6 ma of drive to the 6146 grids, then after setting the tank adjustments as recommended in the manual, dip the final and then adjust the loading for spec - all this, of course, into a dummy load.  But first, the bias, clamper, then RF drive need to be correct.

Oh yes, remember that the 300 supply is on when you turn on the filaments - that is one of my major beefs with this design - that the LV supply is always on when the fils are on - be careful 

Al

[The Slab Bacon]

Oh yes, remember that the 300 supply is on when you turn on the filaments - that is one of my major beefs with this design - that the LV supply is always on when the fils are on - be careful 
Al

Al,
     Just about all 100w class table top BA transmitters are that way. The "plate" switch just switches the primary of the seperate HV transformer. The Junkston Ranger keeps the HV up constantly and uses the clamp tube to shutdown the final in standby.

They all will git ya ifn you aint careful....................

[w1vtp]

Oh yes, remember that the 300 supply is on when you turn on the filaments - that is one of my major beefs with this design - that the LV supply is always on when the fils are on - be careful  
Al

Al,
     Just about all 100w class table top BA transmitters are that way. The "plate" switch just switches the primary of the seperate HV transformer. The Junkston Ranger keeps the HV up constantly and uses the clamp tube to shutdown the final in standby.

They all will git ya ifn you aint careful....................

Yer right Ralph - I still don't have to like it.  I've mentioned this before.  The Eldico TR-1 designers had smarts enuf to put the Fils, LV, HV PWR switches in series so you could first just turn on the fils.  The sequence was to start with the fils (866a rect tubes liked that)  Then if you wanted to run the exciter to the 813, you could turn on the LV.  That's where you would check the grid drive. When you were ready to xmit you would  turn on the HV and key from RX to TX using the LV switch. That way the LV wasn't on unless you wanted it.  When I designed my first 500 watt push pull 813 xmtr, I carried that idea over to  it and it worked great.  Just ignore me -- I have a thang about the way EFJ does it with all their xmtrs (not sure about the KW).

Al

[The Slab Bacon]

Al,
    It wasn't just EFJ, Griefkit did it on the apaches and dixie 100s as did many others. It was pretty common practice back then. It also helped keep production costs down, eliminating the need for an additional transformer and it's associated wiring.

I also like the way Eldico did it with 3 switches. It also helps eliminate those
"it went up in smoke while it was in standby" crapouts.

[KM1H]

I like the Globe 300/350's, only bias at turn on, LV B+ with the exciter switch up and the 1000V with the plate switch or PTT. The down side is lots of noisy relays. Dont know about the bigger models.

Carl