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Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders. |
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In Reply to: well...now i still don't know what to do! posted by replicant808 on November 1, 2001 at 06:15:44:
Only you can decide whether the risk is worth it, but...1. I've exchanged emails with Eric Barbour on the topic of NOS PIO caps and he went out of his way to stress that the "oldies" are filled with PCB's (extremely carcinogenic) and that if one explodes/leaks you have essentially a toxic waste disposal problem in your listening room. Prolonged breathing of the fumes *will* cause health problems, so you have to rip out carpeting, destroy upholstered furniture, drapes, etc. He recommended never exceeding 80% of the rated voltage, allowing for power spikes/shorts. This leads to...
2. Allowing for power fluctuations - assuming you're building a 1200VDC supply, and use 120VAC wall voltage, a 10VAC spike may produce a 100VDC spike (simplifying for the purposes of discussion). Thus you need at least 1300VDC capability, plus 20% for safety now has you running caps rated at 1560VDC.
3. Another way to get hi voltage capability is to stack caps in series with resistors across them to equalize the voltage. The downside is this reduces the total capacitance. You must also take into account that most resistors have a limit for working voltage of 400V across them so you may want to use resistors in series too. By stacking the caps you can safely handle higher voltages.
4. I've had more than one amp repair tech recommend sticking with the conservative 1.4xVAC = VDC rating formula to keep you out of trouble. This consensus opinion comes from years of repairing blown amps so it may be a bit pessimistic. But then again...
Good luck and may the force be with you,
Pete
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Follow Ups
- Some additional cap rating thoughts... - petef 10:27:27 11/01/01 (0)
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