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#1
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Damper diodes as rectifiers
I've seen people use dampers as rectifier before, and I like the
premise.. but something confuses me. In the datasheets for 6AU4, 6AX4, etc, they state that "use of this tube as a power rectifier is not recommended". Why is it not recommended? I don't see any flaws. |
#2
Posted to rec.audio.tubes
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Damper diodes as rectifiers
Maaark wrote:
I've seen people use dampers as rectifier before, and I like the premise.. but something confuses me. In the datasheets for 6AU4, 6AX4, etc, they state that "use of this tube as a power rectifier is not recommended". Why is it not recommended? I don't see any flaws. Not sure either, but be sure to not exceed the peak current rating. In rectifier service, such a tube will see a big peak of current as it tops off the B+ filter cap. Just like regular rectifier tubes. But maybe those can take more abuse (a 5U4 is directly heated, vs a damper which is indirectly heated). Choke input filters should help with this here. A nice feature of most damper diodes is the high voltage ratings for heater-cathode. Which means you should be able to run the heater off a grounded heater supply. Also makes for slow B+ turn on. A downside with damper diodes is that virtually all of them have only one diode inside, so you'd need a pair of damper diode tubes to replace say a 5U4 rectifier. |
#3
Posted to rec.audio.tubes
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Damper diodes as rectifiers
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#5
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Damper diodes as rectifiers
In article Hs%hi.77733$NV3.12353@pd7urf2no, Maaark
wrote: I've seen people use dampers as rectifier before, and I like the premise.. but something confuses me. In the datasheets for 6AU4, 6AX4, etc, they state that "use of this tube as a power rectifier is not recommended". Why is it not recommended? I don't see any flaws. An interesting question, didn't the damper diode provide the boost B+ in old Televisions, which essentially makes it a power rectifier? I wonder if the "not recommended" might have something to do with the published ratings being given for operation at the horizontal line frequency, not power line frequencies? Regards, John Byrns -- Surf my web pages at, http://fmamradios.com/ |
#6
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Damper diodes as rectifiers
Maaark wrote:
In the datasheets for 6AU4, 6AX4, etc, they state that "use of this tube as a power rectifier is not recommended". Why is it not recommended? I don't see any flaws. I'm guessing that statement was meant in the context of power supplies of *television* power supplies. Most of the older TV's with power transformers and rectifier tubes that I've seen had 5U4, 5V3 or 5AU4's, probably because they warm up right away, and cool off a lot faster, although there may have been other considerations. Marantz ignored that warning, BTW, and I don't recall ever hearing about any problems relating to them in the Marantz amps that used 6AU4's. -- Ned Carlson SW side of Chicago, USA www.tubezone.net |
#7
Posted to rec.audio.tubes
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Damper diodes as rectifiers
robert casey wrote: Maaark wrote: I've seen people use dampers as rectifier before, and I like the premise.. but something confuses me. In the datasheets for 6AU4, 6AX4, etc, they state that "use of this tube as a power rectifier is not recommended". Why is it not recommended? I don't see any flaws. Not sure either, but be sure to not exceed the peak current rating. In rectifier service, such a tube will see a big peak of current as it tops off the B+ filter cap. It's quite normal with silicon rectifiers for the peak current to be ~ 10 times the average. I expect the voltage drop of thermionic diodes reduces that ratio but I dare say these diodes weren't intended to pass such high peaks. Graham |
#8
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Damper diodes as rectifiers
It's quite normal with silicon rectifiers for the peak current to be ~ 10 times the average. I expect the voltage drop of thermionic diodes reduces that ratio but I dare say these diodes weren't intended to pass such high peaks. Looking at various data sheets, it looks like a tube can handle only about 5 times its average. It's something one needs to pay attention to. |
#9
Posted to rec.audio.tubes
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Damper diodes as rectifiers
Maaark wrote: In the datasheets for 6AU4, 6AX4, etc, they state that "use of this tube as a power rectifier is not recommended". Why is it not recommended? I don't see any flaws. Hi RATs! Um, some folks used WE 300B tubes as diodes. No accounting for design muses. This is not a mystery. Back when everybody made tubes, it was common to diss "cross applications". RCA radios had stern warnings: "Use RCA tubes for best performance." So did many other brands ... some skepticism is recommended. Of course, if you use TV dampers for a power supply and your dick falls off, you can't say they didn't warn you. Hi-Fi means whatever you think it means. Even if you are really, really smart or whatever Happy Ears! Al |
#10
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Damper diodes as rectifiers
They advised that damper diodes be used only for their intended function for a reason. Which could just be marketing.... But not likely, as no damper diode ever had two separate plates like regular rectifier tubes had. Operation at less than specified filament voltage, or asking them to pass current before they are are fully warmed up, will cause shortened life. And even if operated "properly", the only effect will be that they have a sharper cutoff on the negative portion of the cycle, just like a silicon diode. So if silicon diodes are bad, the damper diode is too. Other indirectly heated rectifier tubes, like the 6X4, would also have that issue. |
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