A Kenwood TL922 linear amplifier with 2 × 3-500Z valves is one of the best, sturdiest and compact build pieces of equipment for radio amateurs. It is equipped with double shielding in a cabinet of thick material with sturdy handles. It is designed with good quality components and there are separate transformers for the HV and filaments. If the HV transformer overheats a thermal safety device incorporated inside it will operate and disconnects the bias. When you switch off the amplifier, the cooling fan will carry on for a few more minutes. These are all features not present in a lot of current models. This is good advice if you come across a 2nd hand one , however there is always room for improvement.A stable TL922 on 9 bands was the result after implementing modifications, like the length of the coax cable between exciter and amplifier, all grids direct to ground (no capacitors) and an extra earth wire to VC1. See:
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