I once owned an Ameritron AL-80B and was quite impressed with it performance, design and build quality. I was regretful soon after I sold it, but a few years later I decided to build my own.
I was working away from home at the time so progress was slow initially, with the metal work part of the build progressing only on the weekends that I travelled the 300 kilometres to get home and there were no other household jobs to be done once I got there. Over a period, I bought quite a few original parts that were listed in the MFJ catalogue including meters, band switch, plate choke, input tuning board etc. Suitable variable capacitors were already in my collection of parts. I studied many photos of the AL-80B available on-line to follow the RF deck layout as closely as possible. I had an original top cover so this formed the basis for all dimensions required when building the chassis.
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 @ 15 Amps. 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 a rash decision... A first for me!
I was working away from home at the time so progress was slow initially, with the metal work part of the build progressing only on the weekends that I travelled the 300 kilometres to get home and there were no other household jobs to be done once I got there. Over a period, I bought quite a few original parts that were listed in the MFJ catalogue including meters, band switch, plate choke, input tuning board etc. Suitable variable capacitors were already in my collection of parts. I studied many photos of the AL-80B available on-line to follow the RF deck layout as closely as possible. I had an original top cover so this formed the basis for all dimensions required when building the chassis.
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 @ 15 Amps. 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 a rash decision... A first for me!
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3-500Z HF Linear Amplifier
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It is planned to have the front panel labelling professionally screen printed.
Page last updated on 25th August 2018
