I too, have had an ongoing issue with the band switch in my FL-2100B. After repeated band switch repairs (replacing contacts you did) I ultimately found my problems were being caused by a keying delay with the buffer relay I was using between the radio and amp. After the 3^rd?failure, I got the O-scope out and measured the keying delay and much to my surprise it was I ended up solving my problems by using a solid-state buffer called a Keyall (). It has an opto-isolated input and with the pair of MOSFETs can switch positive and negative voltages. There are similar devices that require no assembly on the internet. However, I liked the cost of this device over the other options I was able to find and I just made my own enclosure. Because I had so many failures, I ran out of donor contacts for the band switch. I elected to step up and purchase the Multi-tech band switch found here:????

The switch is slightly larger than the original and it took a little work to get it installed but it wasn't a big deal.?

The one thing I always do when I tune up is to make sure that I drive the amp with a full 100 watts out of the exciter during the tune up procedure. Once all tuned for max output, I advance the loading control clockwise just slightly, to over-couple (un-mesh the load capacitor) in order to reduce the chance of arc-over. One of the other issues I've seen is where folks think they are going easy on the amp by tuning the amp at reduced drive levels. The problem is that most radios have ALC-overshoot issues which causes a momentary spike during key up. This spike is really hard on components and can create arcing in the tank circuit. Always a good idea to tune for max power out. If your radio produces significantly more that 100 watts out, then use an attenuator.?

Good luck!

73,

Jim - AA7CL??