Welcome to 4Z4TL QRO page - the Kenwood TL922 amplifier modification project
This page describes various aspects of fixing & modifying a recent acquired Kenwood TL922 linear amplifier. The amp wasn't functional but was indeed in very good shape mechanically & visually. It was never modified in any way but appeared to have been opened and fixed, The obvious problems were no power out , no metering & lack of lights of any sort. The inside inspection revealed a burnt RF choke, burnt meter and TX/RX lamps, several dead diodes & resistors, a dead bias Zener , a broken "leg tab" on the left panel and lack of any protection against various ill conditions. This is how some of it looked like in August 2009:
|Inside - top||Inside - bottom||Burnt RF Choke||Bias Zener area||Meter board|
Research for resources on the web revealed tons of correspondence in the amplifier lists, and several very well known sites holding almost all one needs to begin the task. I duplicated (to a good extent) many mods from Frits PA0FRI, Rich AG6K & Glen VK2FC and in this page I tried to combine the best of all worlds: I bundled many resources and added few of my own which evolved during the project.
TU Rich, Glen for your assistance. Many thanks to all who replied my queries and suggested their clarifications; thanks to my friends from 4X-land Morel 4X1AD, Aaron 4X1FQ for their guidance and thoughts, and special thanks to my good friend Yaakov 4Z5AY for mentoring me and practically helping me get through this project.
I hope you'll find the description and information useful. Good luck
in your own project!
73, Isaac 4Z4TL
So what have I done?
The following are my fixes and mods. In my opinion all are needed, & most are mandatory. Each item's link will open more detail. (No particular order is governing the list hihi...)
|Step start ( more)|
|AC ports rewiring (more)|
|Filament Xfrmr fuse (more)|
|HV fuse (more)|
|Glitch Resistor (more)|
|Cathode feedback (more)|
|Symmetrical feed (more)|
|Plate cap GND (more)|
|Meters leds (more)|
|PTT & relays board(more)|
|RF choke (more)|