Paul: If you are not a purist in your effort to "restore" this tube amp, INSTEAD of replacing the multi-section electrolytics you can just use "single" axial lead or radial electrolytics. As long as the multi-section is not shorted or has excessive leakage you can just leave it in the circuit and connect the new, single electrolytics to the multi-section electrolytics terminals underneath the chassis, leaving the top of the chassis looking "original.". The newer high voltage electrolytic caps will be much smaller than from decades ago so the job will look quite good. As far as the signal caps are concerned, I would not bother with them unless you have found degraded performance or confirmed that the original signal caps are faulty or leaky. The most important of the signal caps will be the coupling capacitors to the grids of the power output tubes..... probably 0.1, 0.22, or 0.47 uf @ 400 or 600 V. Then, of course you will want to test and/or replace the vacuum tubes.... again, the most important will be the expensive output tubes.... and of course check the preamp tubes for performance and possible microphonics.
-- Best Regards, Daniel Sofie Electronics Supply & Repair
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