[Prev][Next][Index][Thread]

Radio interference on new install.

                                                                            
            12-8-95
Hi all,

I just installed a sign that's giving me a radio-interference problem,
thought I'd query folks here for any _easy_ answers before I head off and
get serious about solving it. 

The problem I'm having is buzzing in the TELEPHONE (a new one on me).
Classic 60-cycle hum which, while still possible to hold phone
conversations, is annoying and needs resolving.

The installation is two horizontally-mounted neon rings, 11' diameter, one
hanging six inches above the other. Each ring is composed of six 12mm tubes
approximately 6' long; total 36' per ring, all argon-filled except one tube
in one ring filled neon. Each ring is on its own 12,000 / 30 outdoor-type
drop-ceiling-mounted transformer, Actown brand (which I'm generally
less-than-thrilled with, but gotta use up my old stock.) The meter-tested
load was in the range of about 9,500, so the 12k trafo is underloaded.

I wasn't informed of the phone buzzing until I was back at the site for
other reasons, sans tools, so I was only able to perform minimum
diagnostics. My first thought was that it was the transformer-lead
electrodes being very close to each other (it being a circle), even though
there was no buzzing. I seperated them to about 3" apart; no difference.

T-leads are short, about 4' in each. They pass through a ceiling tile
reinforced with wood; in other words, they pass by no metal.

Phone cable was not in any obvious proximity to neon or wiring.

The "tube supports" are acrylic tubes about 10" long, hung by stainless
cable from the drop ceiling metal grid -- the cable is no closer than 4" to
the neon at any given point. Basically the neon is floating in space with no
metal anywhere near.

My next steps troubleshooting will be to 
        1) Dig out recent ST article by Wayne Strattman on this subject
        2) Disconnect transformers one-at-a-time to determine if it's both
or just one.
        3) Swap out different brand transformers -- one very weird problem
that also happened is that, at 5 in the morning on this all-night install, I
couldn't get the tubes to light and I was damned if I could figure out why
(sometimes don't you just want to cry?).  The transformers, though new and
in the boxes, had the peculiar Actown-in-damp-environment problem of
corrosion on all the terminals. After triple-checking everything and still
only getting a very dim light at the transformer-end tubes, suddenly there
was a kind of crackling sound and one ring lit up bright. By plugging and
unplugging the second transformer in a number of times the same thing
happened with it, and they've been running about a week now.

        Oh, and, to top it off, the employees reported that one of the
electrode-jumps mid-circle was visibly smoking, so they shut it off the day
after I installed it. That was why I'd gone back the first time. I pulled
apart the connection, found nothing loose and no sign of any burning, ran
the tubes awhile and they ran cool.....any suggestions? Call the exorcist?

        Thanks for any ideas, and I'll report on the outcome.

-Ted Pirsig
Follow-Ups: