APACHE MOD CURRENT CHANGING

[ve6pg]

...HI FROM TIM...MY APACHE'S MOD CURRENT KEEPS CHANGING..I REPLACED THE POT BELOW THE RIG,TO A POSITION NEAR THE BACK. THE REASON WAS THE STUPID IDEA OF LIFTING UP THE RIG,TO CHANGE THE SETTING...ANYWAY,THE RIG STILL HAS AN ISSUE WHEREAS,TODAY THE CURRENT RESTS AT 50MILS,BUT IT COULD CHANGE FROM DAY TO DAY...40MILS ONE DAY,60-70 MILS THE NEXT....ANY IDEAS?....TNX....SK..

[W3NP]

Since your HV is probably stable, I would check the screen and bias voltage and note which seems to be changing the most when you are at 40 ma idle vs 60--70 ma. Have you swapped out the mod tubes?

[WA1GFZ]

check with a scope you may be going into ultrasonic oscillation. See if the neighbor's dog barks when the current goes up.

[ve6pg]

...CANT CHECK THE NEIGHBOUR'S DOG...I KILLED HIM WHEN MY 20V WAS ON 160,AND HE GOT TOO CLOSE TO THE RADIALS...BANG...ZAP...POOCH NO MORE...SK..

[W3SLK]

Tim said:

CANT CHECK THE NEIGHBOUR'S DOG...I KILLED HIM WHEN MY 20V WAS ON 160,AND HE GOT TOO CLOSE TO THE RADIALS...BANG...ZAP...POOCH NO MORE...SK..

Gee Tim, remind me never to pee on your fence while the 20V is on the air

[K1JJ]

Hi Tim,

A good technique is to get the rig on it's side and key it into a dummy load.  Get out the plasdick end of a screw driver and start tapping all of the components, tube sockets, connections, etc associated with the tubes having the idling current problems. 

Take a VOM and clip lead on to the important points, like Frank said. Bias, bias pot, screen, cathode... check everything for change as you tap around.  This will at least eliminate poor connections or intermitant parts.

Otherwise, you will need to take measurements on all vital points, write them down, and check them all again when the idle current changes to identify the particular area that's changing.

Let us know if this helps. if not, report back.

73,
T

[Pete, WA2CWA]

In addition to some of the things already mentioned.
Although the book says set to 50 ma; 40 to 60 won't cause the Apache to go belly up. Dirty meter swtich contacts in the "Mod" setting could change your meter reading each time you switch to it. If the pot you're using is old and/or used, it may need to be cleaned. Meter shunt for mod position might be breaking down. AC line voltage variations will cause the meter to read slightly different. Meter itself may not be swinging freely all the time causing the meter pointer to stop at incorrect readings.