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In Reply to: I think I fixed the problem with my Beveridge OTL DD amplifier posted by Lew on October 13, 2020 at 11:50:29:
In repairing these power supplies, I am replacing the electrolytic capacitors. As noted elsewhere, 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. 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 just mental masturbation? Thanks.
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Follow Ups
- Question about capacitor ratings for the cognoscenti - Lew 11:31:50 10/20/20 (2)
- When that thing was built - Ralph 13:27:27 10/20/20 (1)
- RE: When that thing was built - Lew 14:32:02 10/20/20 (0)
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