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Service Manual for Armstrong 521 amplifier, 524 FM Tuner and 526 Receiver

Does anyone have any copies of Armstrong service manuals or circuit diagrams for the following models 521, 524 and 526

Armstrong 521 amplifier service manual


I need Armstrong 521 amplifier service manuals.
It is to do repair.
I desire that show if there is somebody circuit diagram or service manual.


Best Regards.