This project came about just because I came across a top cover for an Ameritron AL-80B Linear amplifier at a good price somewhere a few year ago. I put it aside with the thought in mind that it might come in 'handy' one day. This one was one of the more sturdy aluminium ones rather than the thin steel type used in later production units. The original intention was not to make a copy of the AL-80B as I already owned one at the time.
In 2014 when I had the urge to build something again and the AL-80B had been moved on some years before this project started taking shape in my mind. I was working away at the time so progress was slow with the metal work only on weekends where I made it home and there were no other household jobs to be done. I bought quite a few parts from the MFJ catalogue including meters, band switch, plate choke, input tuning board etc. The variable caps were already in my collection of parts. I studied many photos of the AL-80B on-line to follow the RF deck layout as closely as possible.
The power supply and control side of the chassis is where I used my own ideas and physical layout. The filament transformer used was originally from a 12V PSU and the secondary was rewound for 5 Volts. The plate transformer is one from a Kenwood TL-922 so it is lightly loaded in this one tube application. This was a very time consuming project but one that I really enjoyed, once I came to terms with the fact that it was not going to be completed 'overnight'. This then gave me time to really think about the layout and associated metalwork & wiring etc. Whenever I came to a 'stumbling block', I would put the project aside for a few days to think about the next move. At one point of the construction I had concerns that I was not going to get all of the circuitry I needed into the power supply side of the chassis. I tried a number of layouts before settling on this final one. As a result of not rushing through this build I can say that only one extra and not-needed hole was drilled in the chassis as a result of making an error of judgement... A first for me!
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Page last updated 13 April 2018