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Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Well, Got the tube today. I cant really test it besides the filament. So, I have a mot primary in series with the filament transformer. This puts out 6V to the tube. When I give the tube power, it slowly goes from off to medium glow. after 30 seconds (settings on the relay) it shorts the mot primary, and is in 12.6V full gear.
Besides building an entire coil, is there an easy way to test the tube and make sure it performs?
Registered Member #4108
Joined: Sun Sept 25 2011, 11:43PM
Location:
Posts: 149
The gu-81m is a very well built tube, I have doubts that it will get damaged. I smuggled my on my luggage from Praha.Since then I bought another one on ebay, and I have had no issues.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Okay... I kinda figured "hey mabye i can just use what i got around the house and wire it up, least to see if i can get even 1mm sparks" using film caps to 10-50nF on everything .. well, i guess not. because i fired things up today, changed polarity of the tuning and primary, got nothing. Guess im forced to get door knob capacitors, i tried using WIMA 0.1uF 1600V caps, to at least TEST the tube and see if it can do something. never got anywhere.
For now, im using a 300khz secondary, 3.5 x 12 inch. one schematic showed the tuning coil below the primary...so, i put the tuning coil about 1cm above the first turn, and the primary just above it..so 2" up the coil. Either way, i never got a thing.
As far as the schematic and WIMA caps go... Here's the edited version.
I figured id least get a TINY thing at most to prove the tube works.
I used jake's schematic, seeing he is using the same tube. Now, my biggest question. The tube diagram shows the center grid's left tap, is the cathode on the top. Now, i used the right side of the grid, pin 6. Is this okay? Everything else is on the left side of the grid..pins 4 and 3...is it fine i did pin 6 tot connect all the grids together?
thought id get something at least, a little spark maybe, but guess not...guess i have to get real size caps.
Registered Member #2939
Joined: Fri Jun 25 2010, 04:25AM
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Posts: 615
Are you sure thats the right way to wire for triode operation? reading around the net suggests the suppressor grid should still be connected to the cathode, and the screen connected to either plate (via a resistor) or to control grid.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
2Spoons wrote ...
Are you sure thats the right way to wire for triode operation? reading around the net suggests the suppressor grid should still be connected to the cathode, and the screen connected to either plate (via a resistor) or to control grid.
What, This?
Im new, i dont know this stuff, i saw jake got it working, and figured that was proper.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
What voltages should i expect things to kick on at? i mean i variac my mot, sohuld i see streamers and stuff below 40V input to the mot? right now i got the 2 grids tied, and 1 on the neg, as the diagram shows. still havin issues, maybe my shitty setup but still should do something except glow..
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I want to build my first VTTC...
