Being Neutral / Valiant

[ka4koe]

Manuals can be a very good thing for the ham faced with an impending mass of tubes, wires, and heavy iron.

I tuned the final as per the manual into a dummy load. 7.5 mA grid, dipped the plate, adjusted the coupling. Hmmmmmm......

Plate current running around 475 mA, instead of the 450 specified. Backing off the drive to 450 mA killed the power output.

Pulled out the handy dandy Valiant manual and it described just this very condition. Imagine that!!!

Note that the power output in CW mode was between 150 and 200w.

Seems a good neutralization will be on the list of tasks facing me when I take the cover off the Valiant.

PHILIP
KA4KOE

[Steve - K4HX]

If you want less output, load the transmitter less. Backing off the drive will always kill the power output on a Class C rig.

Not saying the rig doesn't need to be neutralized, but once the drive is reduced below a certain point, the power output will drop, no matter what.

[N8ETQ]

Hey Philip,

    I wouldn't get too excited about a 25ma diff. on a valiant meter, those
"Nichrome" wire shunts were crazy, You may want to verify PA Bias while
your under there as well.

   Wonder what band you were testing on? Neutralization prolly
won't be a big deal on 75 or 40.  Like Steve said, set the course
and the Fine loading at zero and "Dip and Load" one step at a time
using only the "Course Loading Switch"
till you get to a bit less than you shooting for, then Dial it in with the
Fine load.   BTW if you find a couple positions of the course load
control that don't seem to make a change in Ip you may have some
bad loading padders. Does yours have the two pots on the side
for bias adjustment?

73

/Dan

[ka4koe]

I haven't had the cover off of it yet. First priority is a three conductor line cord. I was thinking of a PC cord, but typically those are too big to fit in the existing grommets.
Already found out there is significant voltage on the CW key. It zinged my hand while practicing on the Vibroplex into a dummy load.

I was tuning up on 3885 Khz.

PAN

[Ed/KB1HYS]

I've done the same thing a few times.  Easy to forget there's some hefty volts on that hardware.

[ke7trp]

Make sure not to switch the Course loading control while the plate switch is on.  If you do, the contacts will arc on the switch and they could be damaged. Unkey the rig, Turn the course knob, Then key it back up.

[WA2TTP Steve]

There are some forbidden course loading positions on some bands. There spelled out in the manual. You can damage the band switch due to circulating current. I'd give more detail but I'm away from home.
Good luck,
Steve

[W6TOM]

 I replaced the crummy nichrome shunts with precision wire wound resistors from Mouser.

[N8ETQ]

  look here,


http://amfone.net/Amforum/index.php?topic=33541.msg259550#msg259550

/Dan





Key Point's:

Stupid line
cord plug, No "Back to Back" diodes across the "beautiful"
Teardrop meter and Internal LV Fuse Holder.