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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: Rectifier Flashing.... posted by Derick on September 6, 2002 at 23:29:59:
5V4s do not have (to my knowledge at least) any form of "instant- on" filament; this would be redundant as an indirectly heated rectifier solves the cathode stripping issue for output and front-end tubes. While an "instant on" might help the lifespan of the rectifier, the materials used for this special filament type will not bear the temperatures and electrical loads generated in a 2-3 ampere heater-- hence its' use in small signal tubes exclusively. (If power tubes could be made with it, the delayed ramp up of the DC w/ indirect rectifiers would be unecessary.) The flash you saw was an internal arc caused by the excessive voltage and current demands meant for a 5u4; it only did it once because (sorry) you damaged the emission capabilities of the tube. When subbing rectifiers, look in a tube manual for 3 critical ratings: 1. Filament Current-- a GZ34 is 1.9 amps and there are common rectifiers that draw 3+ amps 2. PIV (Peak Inverse Voltage) This figure is double the operational B+/DC of the amp. 3. Maximum capacitative load. The 5V4 and 5R4 are the lowest, at 10 and 20 (I think) respectively. If you wish to add more storage, add a small choke (1-3 henries, 200 ma or so-- Ned at Triode Electronics has them) and connect one choke lead to the small 1st cap (10 uf for a 5V4) and the other choke lead to a 100 uf or so electrolytic bypassed with a 10-20 uf Solen FastCap. If the bypass uf value is any less than 3-5% of the larger caps' uf value the benefits will manifest only in the extreme high frequencies. I have a computer modeling program that shows curves of various chokes and capacitors with and w/o bypasses; for example, a .1uf bypass on a 100 uf 'lytic will have no effect below 15,000 hertz. Chris
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- Re: Rectifier Flashing.... - Chris Spafford 08:22:47 09/07/02 (0)
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