Thank you, Kurt. Brilliant advice/great reminder about dust. Much
appreciated.
I grew up on rumors about how the Henry Radio repair shop would take a
Collins S-Line in for repair, throw it in the bathtub, and take a hose
to it. It always amazes me how "we as a society" somehow automatically
assume water is bad near "electricity" without knowing more of the details.
Maybe it comes from that movie they showed us in 4th grade where that
lady at the county fair tried to change a light bulb while standing in
water. Lots of sparks and screaming. It gave me nightmares but I got
over them. She should probably not have stuck her fingers into the
socket without turning it off first. But that might have been an issue
even if she wasn't standing in water.
Still trying to understand the sparks.
Mark N5OT
On 2/12/2021 6:40 PM, KD7JYK DM09 wrote:
"Just sitting there, it started making an arcing noise (sort of) and
showed plate current jumping around. "
New here, so mostly lurking, but this brought back memories of many
issues over the years. Have you checked for dust? I've run into this
many times, especially in TV's, and video displays, my experience with
tube amps is limited, although I have a few. Hyper-fine dust sticking
to things, and causing tracking, and eventually arcing. I took apart
a hallicrafters TV to show to a friend (assuming the issue would
exist), and there it was around the high voltage rectifier tube, fine
dust, with some blackened areas due to corona.
One of the very first things I do when inspecting, is gently blow out,
or vacuum any dust, and if possible, wash parts, boards, frames,
cases, connectors, et cetera before applying power, especially with
high voltage circuits.
Depending on the component, I use 91% rubbing alcohol, or QD Electric
Contact Cleaner, then let dry very thoroughly. Sometimes I use a
small, soft nylon bristled brush to scrub away really tenacious crud.
Kurt
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