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Registered Member #1733
Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100
I'm looking into buying a couple variacs, one 10A for my bench, and an unknown for building my VTTC. Using smaller Pentodes, what would be the "typical" amperage draw? The pentodes I currently have are 700V plate (17DQ6B), and 2 larger types that I'm missing the specs on ATM. I have the desire to build a small single tube TC, and a quad. I can get 3A 120V variacs for $25, would that be enough?
I have no specifics on the TC's yet, I'm just gathering parts.
Registered Member #1733
Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100
Thanks guys... The variac's I'm looking at are tiny (2" L x 2.25" D) 132V 3A for 396W. The Tubes are 700V max, 0.65A. So if I run them at 600V I'm at 390W.
Going to use a MOT to power it, everything encased together. The tube max temp is 220C. I have not seen (that I recall) VTTC's with cooling fans. I have some 12-18V fans doing nothing... Should I be concerned about heating in the MOT and the variac?
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
The maximum anode dissipation of 17DQ6B is 18W, so its high peak pulses must be limited to 1/15th of one 525-line scanning cycle - about 18us - such that the duty cycle does not cause anode dissipation ratings to be exceeded.
Registered Member #1733
Joined: Thu Oct 02 2008, 03:17PM
Location: Hamilton, ON, Canada
Posts: 100
Thanks guys...
I know the 17DQ6B is small relative to the VTTC's made by others here, but here's hoping. I had to clean up my computer lab at work yesterday, and was able to scoop some nifty things. Two 250V line filters, two 250V 25A breakers, two 20A buss bars, and another UPS xfmr. The UPS boards had 2 small mains transformers on them, 120V primary, 15-16V secondary @ 500mA.
I also have electrical contractors here putting a new isolated panel in my lab. His company does a lot of industrial work, so I asked if he could source some really cheap (like free) used variacs. I'm also trying to get in their used parts warehouse to go "shopping"...
My uncle works at the Nuke station here, but he can't get me anything from there... Damn Govt...
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Variac for VTTC
