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*To*: tesla-at-pupman-dot-com*Subject*: Re: VTTC output*From*: "Tesla list" <tesla-at-pupman-dot-com>*Date*: Tue, 20 Feb 2001 06:48:05 -0700*Resent-Date*: Tue, 20 Feb 2001 07:12:04 -0700*Resent-From*: tesla-at-pupman-dot-com*Resent-Message-ID*: <rLiIV.A.HEE.wsnk6-at-poodle>*Resent-Sender*: tesla-request-at-pupman-dot-com

Original poster: "Herwig Roscher by way of Terry Fritz <twftesla-at-uswest-dot-net>" <herwig.roscher-at-gmx.de> Ed Phillips wrote: > > Trying to max out my system I connected a 5 Ohm resistor > > between the base of the secondary and rf ground. I scoped the > > voltage across this resistor and found it to be 20 Vpp at low input > > power levels. > > Increasing the input power real streamers started growing from the brush, resulting in about 40 Vpp across the resistor. Obviously streamers have a lower resistance than the brush. >From 40 Vpp an effective current of about 2.5 A is calculated and I'm wondering when the AWG 26 will become hot. > Probably won't get hot. Your secondary has a lot of area and, when you > calculate the total dissipation and divide it by the area, you will find > the power density (watts/square inch, centimeter, or whatever) is quite > low and easily cooled by convection. Ed, I've just finished another series of tests: Using 15 kOhm/1.6 nF as grid leak combination and a Vg2 of 1200 V, the plate current was 480 mA at a plate voltage of 8600 Vdc. Seems that I reached the limits of my tube ;-) The tank caps became barely warm and the primary coil reached about 30 deg C after a few minutes of testing with various loads. But the lower part of the secondary became so hot that I hardly could touch it (more than 60 deg C ?). Trying to find a possibility to "measure" the relative output power instead of guessing it by eye, I've used - the a.m. 5 Ohm resistor - a pickup coil of 4 turns wound on the form of the primary at a distance of 3.5" and connected to a 230 V/100 W bulb. The voltage across this bulb is 130 Vpp and nearly independent(!!) on the power output. I was really surprised that the system is so insensitive. Could the reason be that I'm using a tetrode which has a very high plate resistance in comparison to triodes? If I calculated the tank voltage from 67 turns of primary / 4 turns of pickup coil and multiply it by 130 Vpp, I get 2200 Vpp. IMO this is low, taking into consideration the plate voltage of 10 kVdc. Any hints or comments? Bye Herwig

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