is it nessary for the standby s/w to pre heat tubes on the eiclone.
what is the seaquence of use.
1-pre heat for how long.
2-main power on.
3-shut-off standby s/w
on shut down reverse procedure.
4-dont see anything about it in manual.
pre heater [ standby s/w ]
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pre heater [ standby s/w ]
by audioray » Wed Sep 22, 2004 6:13 am
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Re: pre heater [ standby s/w ]
by Shannon Parks » Thu Sep 23, 2004 6:33 am
audioray wrote:is it nessary for the standby s/w to pre heat tubes on the eiclone.
Not necessary. Most classic amps had no preheat switch. It is seen as a $1.50 insurance policy.
audioray wrote:what is the seaquence of use.
1-pre heat for how long.
2-main power on.
3-shut-off standby s/w
on shut down reverse procedure.
4-dont see anything about it in manual.
Power Up:
1. Preheat at least for 30 seconds to get any use of the standby switch. One minute is great.
2. Main power on.
When ready for shutdown:
1. Main power off.
2. Let some of the power bleed then Standby off.
Shannon
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by erichayes » Thu Sep 23, 2004 9:44 pm
Hi All,
It's been known for quite a while that allowing a tube to run at nominal (normal) heater voltage with no B+ applied causes the cathode to "bake", thus reducing its emissive capability. This is particularly true of power tubes such as those used in the Dyna and Eiclones.
A nifty way to prevent this from happening is to use a double pole standby switch. Wire a 6 amp 100PIV rectifier across the second set of poles--polarity doesn't matter--and wire one side of the heater source and load in parallel with the rectifier.
When the switch is in the "standby" position, the high voltage is disconnected, and the heater voltage flows through the unfiltered half wave rectifier, dropping the voltage to roughly half normal. This keeps the cathodes warm enough to emit electrons when the switch is thrown to the "operate" position, but not hot enough to cause the baking process to take place.
Obviously, when the switch is in the Operate position, the diode is shorted out, allowing full heater voltage to be applied to the tubes, and the other set of poles completes the B+ circuit.
I've been using this gimmick since the late 60s and still marvel at the increase in useful tube life it provides.
It's been known for quite a while that allowing a tube to run at nominal (normal) heater voltage with no B+ applied causes the cathode to "bake", thus reducing its emissive capability. This is particularly true of power tubes such as those used in the Dyna and Eiclones.
A nifty way to prevent this from happening is to use a double pole standby switch. Wire a 6 amp 100PIV rectifier across the second set of poles--polarity doesn't matter--and wire one side of the heater source and load in parallel with the rectifier.
When the switch is in the "standby" position, the high voltage is disconnected, and the heater voltage flows through the unfiltered half wave rectifier, dropping the voltage to roughly half normal. This keeps the cathodes warm enough to emit electrons when the switch is thrown to the "operate" position, but not hot enough to cause the baking process to take place.
Obviously, when the switch is in the Operate position, the diode is shorted out, allowing full heater voltage to be applied to the tubes, and the other set of poles completes the B+ circuit.
I've been using this gimmick since the late 60s and still marvel at the increase in useful tube life it provides.
Eric in the Jefferson State
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