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Quad II question: High B+ a problem?
Hello all, long time lurker/sporadic poster here with a question concerning my current project.
I recently rebuilt a couple of Quad II's from what was pretty bad shape with parts missing etc. Everything now works and sounds great and even looks mostly original... except for the highish B+ Im getting. This is the new configuration: Rectifier tube (5AR4) - 33uF/450v - the original choke - 47uF/450v With 5AR4/GZ34 I am getting around 380-385v at the rectifier. I would like to use this tube since it is more modern than the GZ32/5V4. With GZ32 there is a bit of voltage drop to 372v or so but its still much higher than the original schematic. I raised the cathode R to 220 ohms to go a bit more easy on the few vintage KT66's that I have, and also to be able to use 6L6GC. KT's are showing 29,5v on the cathodes, and 6L6 (old RCA) are at 27v in the same configuration. Do you think the transformers and chokes are up to such a high B+ in prolonged use? How about tube life? Could I try, say, a 5R4 instead of the indirectly heated ones (for the bigger voltage drop) or is this asking for trouble. I would like this rebuild to last long and be trouble free and run as cool as possible within its design limitations. Thanks for reading! Martin |
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