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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I have a Scott 299B tube amp which is in need of restoration. It is
> complete and unmollested, but probably has not been powered-up for a
> decade or two. I would like to replace the signal cap's with
> audiophile grade polys to improve reliability and sound. I am also
> concerned about the electrolytic cap's so I checked all of them in
> circuit with an ESR meter. Out of the 5 multi-segment twist-lock cans,
> 3 have high ESR. One has 2 sections that are dead, and the other 2
> have sections with high ESR (3-9 ohms). I am having trouble finding
> replacement cans, and the ones I found are about $30 each. To me, this
> thing is not worth $100 worth of 'lytics plus the cost of new poly's,
> so I am looking for alternatives. Do I really need to replace the 3-9
> ohm ESR parts? 3 of these are 100uF and filter the DC filament voltage
> for the preamp tubes. Another is 10uF, measures 5 ohms, and filters
> the bias voltage for the output tubes.
>
> Does anyone know of a supplier who has a good selection of multi-cap
> cans at lower prices?
>
> The one that is dead is 20/450v, 20/450v, 25/25v, 25/25v, and is 1.4"
> dia and 2" high.
>
> The high ESR ones are 100-100-10/75v and are the same size.
>
> Thanks,
> Paul