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I have a TS-830S that was initially doing about 60W in CW at 10m and 70W at 40m. I've heard these things are capable of at least 100W.

Determined, I started doing research on what components to look at in addition to the tubes. I'm able to get ALC with CAR at 5 on 40 and 8 on 10 meters- so I think the drive is sufficient. This lead me to suspect the final tubes.

Before getting a pricey set of tubes- I tried some of the cheaper avenues. I have replace the C7 C8 and L1 components of the final cage with a kit from hybridrestore.com. Next- I replaced the cathode and screen resistors with another kit from the same vendor.

I didn't get much power out of that- but I did notice the tubes we easier to neutralize. I use an SDR running SDR# as my second receive and tune to a dip in signal strength with SG.SW OFF. The dip was much sharper and more pronounced- but it could have been placebo.

Finally I decided to try new tubes. I got a pair of NOS tubes from an ebay vendor with lots of good rep. I put them in the radio and "cooked" the getters a bit- maybe 5 minutes- with the SG switch off. Clearly that wasn't long enough, because a tube arched and the resistors went out of spec.

I found some 1/2W metal film resistors on ebay in 100ohm and 20ohm for replacement. And this time cooked the getters for a good hour.

Things appear to be working. And I'm getting about 90W on 40m and 80W on 20m. But I want to get more out of it.

I understand that the power differences here are negligible. This is more for my satisfaction of getting and old rig running at peak performance again.

My question is- what would you suspect next? Maybe the tubes are not quite "NOS" as claimed? Should I try newly manufactured Chinese tubes that haven't been sitting on the shelf for 30 years? Should I replace the HV caps? I'm getting an 800V reading on the HV meter. Anything else to look at next?

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    $\begingroup$ What setup and equipment are you using to measure the Po? $\endgroup$
    – Glenn W9IQ
    Jul 25, 2018 at 16:04
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    $\begingroup$ I've got an MFJ-894 sitting between the rig and an MFJ-260C dummy load. Jumpers all under a foot. Readouts in power look the same if I use a real dipole antenna instead of the dummy load. I just have about 1.5 swr in that case. $\endgroup$
    – user3191449
    Jul 25, 2018 at 17:33
  • $\begingroup$ What is the the grid voltage, the screen voltage, and the key-down idling current with no output? $\endgroup$
    – Mike Waters
    Jul 25, 2018 at 18:04
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    $\begingroup$ Hi Paul, I hope you don't mind but I edited your title to be less model-specific, because surely lots of other people out there with other rigs with tube finals are also having trouble getting full rated output power. In other words, I hope I made your question a little more useful to others. $\endgroup$
    – rclocher3
    Jul 25, 2018 at 18:59
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    $\begingroup$ Ah, hadn't tought of the shipping cost/item value problem. However, if you're in the US, arrow.com is currently offering free next-day shipping, so maybe that's more to your taste. Regarding "HF characteristics": for metal film resistors, just don't worry about the inductivity south of 1GHz; these aren't wirewounds! I'd expect the leads of the resistor to have more inductance than the resistor itself, and you can't do much about that. $\endgroup$
    – Marcus Müller
    Jul 26, 2018 at 16:29

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As a KWM-2 overhauler, I'm impressed with your knowledgeable attack on the problem. Two suggestions:

I would look at the driver stage, and check voltages and the cathode and screen resistors (like you did for the finals) to make sure their output is up to spec.

If you want meaningfully more output, an easy way is to get an amplifier in the 500 Watt class, such as a 30L1, can be had for short money. Makes a huge difference in the quality of on-air conversation.

By the way, gettering generally takes of the order of 24 hours. Time well spent, as you found out the hard way.

73

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