i've built a simple am receiver around a 117n7 tube, but it's not
working.
the only sound it makes is a hum, and the output transformer gets so
hot the wax bubbles out. i can post a schematic if it would help...any
suggestions would be appreciated.

jon s. wrote:
i've built a simple am receiver around a 117n7 tube, but it's not
working.
the only sound it makes is a hum, and the output transformer gets so
hot the wax bubbles out. i can post a schematic if it would help...any
suggestions would be appreciated.

Okay, so there is way more current going through the tube than should be.

What is the difference in voltage between the control grid and the cathode?

Is this thing oscillating? Is it interfering with nearby radios and TVs?
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"jon s." wrote:
i can post a schematic if it would help...any
suggestions would be appreciated.

Need that diagram in order to answer your question...

(Scott Dorsey) wrote in message ...
jon s. wrote:
i've built a simple am receiver around a 117n7 tube, but it's not
working.
the only sound it makes is a hum, and the output transformer gets so
hot the wax bubbles out. i can post a schematic if it would help...any
suggestions would be appreciated.

Okay, so there is way more current going through the tube than should be.

What is the difference in voltage between the control grid and the cathode?

Is this thing oscillating? Is it interfering with nearby radios and TVs?
--scott


thanks, Scott,

yikes! i should mention that i'm a complete neophyte with this
stuff...i'm not sure how to check voltage, or for that matter,
identify a control grid or cathode. there is a steady humming sound,
that doesn't seem to fluctuate at all, and it is not near any other
radio or tv. if i'm not mistaken, the 117n7 is designed to go directly
from an ac outlet without a stepdown transformer, isn't it? is my
household current too high? maybe a faulty tube?
thanks again,
Jon