Hmmmmm... Les see... I don't know this rig, but...

No dip.

You say: "The amp can be tuned though, but I only get 50 W HF out..."

I don't know what "tuned through" means Do tell. Is there any kind of a
PEAK in the output power when tuning either the plate tuning or the plate
loading?

Not sure where to go from here, but these two controls, when not behaving
normally, indicate that either there is not a tank circuit (something is
shorted or open). This could be something in the tank ckt OR the tube.

Getting 50 watts seems to indicate that the plate circuit is NEAR resonance,
so something must be close to right. I'd look @ tube voltages (Be careful)

Ran out of ideas.

73,
--
Steve N, K,9;d, c. i My email has no u's.


"Angel Vilaseca" wrote in message
...
When trying to tune the final amp on my Kenwood TS-820, I get little or no
plate dip.
The amp can be tuned though, but I only get 50 W HF out, instead of 100 W.
Plate current is nominal at 250 mA and 800 V on the 6146B anodes.

I made these measurements with the rig connected to a 50 ohms dummy load
and the HF output was confirmed with a HP 432A power mwter.

So I get 50 W HF out for 200 W DC in. Efficiency is terrible at only 25%.
All the missing HF power must be dissipated in the anodes because they
glow
red after a few seconds.

The same thing happens on all bands. Sometimes, when trying to tune on 7
MHz, plate current gets higher than 350 mA and the rig fuse blows.

I suspect there must be something wrong in the tank circuit.

Upon visual inspection, nothing looks charred in there. No arcing noises.

I checked the plate capacitor, which is OK. I unsoldered it and measured
it
@ .001 uF, as it should be.

So I am wondering where to look next. Any ideas?

many tnx in advance

Angel Vilaseca HB9SLV