Quote:
Originally Posted by dtvmcdonald
A lot of what has been said is hooey ... except, of course, the bad reputation
of the 6x5.
There is nothing in a recapped radio that is going to be hurt by 2N1007 replacing
a 6X5 if the power supply caps are high enough voltage rated, as are the replaced
paper caps. I looked at Zenith schematics from 1941 using 6x5 rectifiers and they had
250 v B+ voltages. With 450 V electrolytics and 630 (or even 400)V film caps,
you don't even need additional series resistance, as the transformer resistance will be
safe for 1N4007s.
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How about the transformer itself? While I agree that in general, power transformers can tolerate overload conditions and in-rush surges, pre-war transformers *may* be a special case. These may just be "old wives tales", but several old-time collectors that I know treat these transformers very gently, arguing that the paper insulation in these transformers contains sulfides (from bleaching) which may attack the copper wire if the insulation is comprimised, leading to unintended internal "fuses" in the transformer. These weak spots can be perhaps blown out by high in-rush currents. They usually are careful to use close to the same value input filter cap (not too much higher) to limit peak currents that might strain the (perhaps) compromised transformer.
jr