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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: twin rectifier power supply 1 SS + 1 tubed? posted by DAK on August 1, 2016 at 22:50:24:
DAK & Co.
I think you may be missing the point of having two tube rectifiers to begin with. It's done that way because more current is needed than the 225ma one 5AR4 can provide. The two rectifier tubes are arranged in parallel. Plates to plates, cathode to cathode.
If you substitute one tube with a SS rectifier, naturally it will turn on immediately and produce an abnormally high voltage until a) the circuit tubes start conducting, b) the 5AR4 starts conducting and the transformer current splits between the two. At that point, the drop across the tube rectifier comes into play and should drop the voltage to a more nominal level.
As for adding SS rectifiers in SERIES with the tube plates, that is done to simply prevent damage to the power transformer should the rectifier catastrophically short out. The SS rectifiers will take over the rectification job and all is well except, the B+ voltage will rise by about 40 Vdc. If your filter caps. aren't rated for the increase in voltage, they could be destroyed.
Finally, if you want more B+, why not just use heavy duty (3A) ss rectifiers to begin with? The cathode stripping theory has been debunked by engineer David Gillispie. Besides, if cathode stripping exists, why don't rectifiers suffer from this? Their plates are brought up to maximum secondary voltage as soon as the power switch is turned on while the tube is still dead cold.
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Follow Ups
- RE: twin rectifier power supply 1 SS + 1 tubed? - pmaneri@samsontech.com 12:51:51 08/05/16 (1)
- RE: Yes, i know all of that.I wanted to have slow B+ - DAK 13:41:22 08/05/16 (0)
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