Question about electrolytic capacitor voltage ratings

Tube DIY Asylum

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In repairing the power supplies in my Beveridge direct-drive amplifiers, I am replacing the electrolytic capacitors. The filter uses eight (8) 47uF/450V capacitors in series with shunt resistors to promote current sharing. These 8 capacitors are in a series string from ground reference to the +3200V node, the output is also tapped at +1600V. With new capacitors and brand new shunt resistors (metal film types that measure near to exactly alike) installed, I am noting that the voltage across each capacitor varies enough such that it is darn near to the upper limit of their rating, 450V, in some cases, especially during warm up. To measure 425V across one or more of the capacitors is typical in some positions. This is likely due to differences among the capacitors in value and/or in ESR or leakage. Operating this close to the limit is bothersome, and makes me wonder whether that (in addition to aging of the OEM carbon comp shunt resistors) was a cause of previous failure. So I started to look for axial lead electrolytics in voltages rated higher than 450V. (High voltage axial leaded electrolytics are very hard to find in the first place.) I have had no luck so far except I did find that Tube Depot sells German-made F&T brand electrolytics that would fit, in 500V rated value. That's the best I have found so far, but I wonder whether the 500V rating constitutes a distinction without a difference, when compared to the 450V-rated Nichicons I have been using. In other words, the capacitor may have met some criterion to establish its voltage rating that is looser than the criterion applied to the 450V capacitors I already have. Does anyone have any experience on this? Would it be worthwhile to get the 500V rated caps or would it just give me a false sense of security? Thanks.

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Topic - Question about electrolytic capacitor voltage ratings - Lew 11:36:28 10/20/20 (9)

what is your house line voltage? - Story 12:57:17 10/20/20 (8)

Variac - Lew 14:25:49 10/20/20 (7)

RE: Variac - Alpha Al 17:41:13 10/20/20 (6)

RE: Variac - Lew 08:00:01 10/21/20 (5)

Yikes! I would not trust those markings! - Ralph 09:57:41 10/21/20 (4)

RE: Yikes! I would not trust those markings! - Lew 14:07:55 10/21/20 (2)

RE: Yikes! I would not trust those markings! - Ralph 15:02:05 10/21/20 (1)

Yes, I am well aware that the voltage will sag a bit when the variac is feeding the Bev amplifier - Lew 16:12:50 10/21/20 (0)

Yes, then adjust the knob position if possible and needed. NT - Coner 11:10:27 10/21/20 (0)

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