30S-1 Filter Capacitors

 

I recently had what could only be regarded as a disaster strike.  While operating my personal 30S-1, one of the 2 main high voltage filter capacitors shorted.  Not only did it make a loud noise, blow fuses and make a mess, it was a significant problem as regards replacement.  Presumably, a long and diligent search will provide me an exact replacement at what I believe is a reasonable expense.  Current pricing for new units that are at least electrical equivalents is approximately $195 and up.  In the interim, I decided to remove both the good and bad units and replace them with a capacitor chain similar to what is used in the 30L-1 amplifier.  The 3KV capacitors that are used in the 30S-1 are operating very near the absolute limit since the DC voltage is 2.8KV nominal.  High line voltage will stress them even further.  By using readily available good quality capacitors some additional margin on voltage rating can be obtained in addition to improved filtering capacity.  The schematic of the old and new are shown below.  The capacitors and 10 watt balancing resistors were mounted on a .0625 thick G10 fiberglass sheet 7 inches square.  Four caps and four resistors were mounted to each side and the sheet then was mounted on 1.5 inch standoffs in the original capacitor mounting holes.  Simplicity is elegance and replacements are “cheap”.