Just took one off the air, was on 89.5 when we put it in but only had to move it to 92.3. Just went looking for that Harris bulletin, but must be on the computer at work.
As I remember, on the grid of the final there is a little link which you shorten as you go up in frequency. It's soldered in place. Also, in the cavity, there is a plate that can be moved as a coarse tuning adjustment on the final.
If you can, find an exciter that will put out about 30 watts or better; and connect it directly into the final. The IPA is connected to the final by a short jumper, on the right hand side of the cavity (looking from the back) you'll see the BNC jack. On ours, the IPA is little more than a buffer amp--an MX15 will drive the final directly to about 1200 watts, I used an 802A to get the full 2500 watts, with around 25 watts of drive. Final grid tuning becomes critical to match the exciter, but once set it just runs.
Also--crawl in the cavity and check the plate loading capacitor. It's a little air variable with three plates; it can come loose over the years and start arcing. Once it does, you are dead. Don't know of a replacement source.
An in-line watt meter is almost necessary. These things were built back in the time of hand-picking finals for best efficiency. On my box the listed efficiency is 74%, never could do much better than 69%, and it REALLY did not want to make full output--usually settled around 2300~2350 watts. My licensed tpo was 2450, so no big problem.
