Re: Laptop video noise -- help

G-squared wrote:
On Jan 27, 11:20 am, pj <pj4...@xxxxxxxxx> wrote:

> Thanks for all the good 'thought nuggets.'
> Particularly, the reminder about the starting &
> protection frailties of switching supplies.
>
> Yup, the 'brick' is a three pronger. Did the
> 2-3 adapter game with no supporting ground.
> Slight difference-- herringbone rode up higher
> in the 60hz bands. Impulse speckles remained in
> about the same area of each band.
>
> Could be a general circulating ground issue.
> There there are grounds all over the place:
> OTA, LAN router, Cable-TV, DVD player, HT, some
> capacitive coupling back through the power
> brick, HDTV at the wall plug. JVC used two
> prongs on that so who knows how they are
> bringing their chassis to 'earth.' -probably
> via another capacitor since this mess isn't
> tripping the GFI.
>
> Checked and found the LAN router & cablemodem
> are on another a.c. circuit --on the opposite
> side of the 120/240 line from the HDTV, notebook
> etc. Pulled the CAT-5 connection to the
> notebook and put it on wireless -- still had the
> noise.
>
> Although this may be a 'mulligan stew' of
> circulating grounds, I tend to blame either the
> power 'brick' or the way HP is powering their
> their S-Video interface.
>
> Perhaps found a work-around. Checked to see if
> the S-Video connector shell was solidly
> connected on both ends and noted a D-15 RGB
> input socket on the back of the TV that I hadn't
> paid any attention. No clue as to how the RGB
> bandwidth will compare with S-Video but will
> stop by Fry's tomorrow, buy a cable and give it
> a try. Might be the way to go -- this notebook
> has done an OK job when hooked to a conference
> room projector and Smartboard. That screen has
> about 2-3 times the area as this RPTV.
>
> (However, the conference room at work has a
> video amplifier between the notebook pigtail and
> the projector so don't know what kind of
> conditioning or filtering that might be doing.)
>
> Thanks again for pushing the 'engage' button on
> my brain.
>
> Now, the pi filter will be a last resort.
>
> --
> pj

One other thought. Are there any antenna or cable/satellite cables
coming into the system? I ran into a hum condition with 2 PCs on the
LAN on different phases of the AC power but connected to a common
antenna via splitters. The video is digital so there was no issue but
the analog audio from the HTPC to the DLP set had a lot of hum. That
was cured by using a galvanic isolator on the antenna feed to PCs
_not_ directly connected to the TV. The LAN connections appear to be
isolated.

GG

Hmmm, good follow up item if the RGB (VGA) cable doesn't do the job. You may have zeroed in on a massive circulating ground.

Thanks again (I think?)...

I had forgotten the OTA antenna amp in the attic which splits to the ATSC input of the HDTV and to an older set in the Family Room.

No direct OTA connections to any PCs on the LAN. The OTA antenna goes into a lo-noise Electroline +7db amp *but* Electroline's transformer connects to that amp with a piece of RG-6 coax so the power isn't balanced to ground. There's probably some 60hz on that amp and on the OTA cables to the TVs. The TVs are in turn grounded to one another through the cable-TV wiring which is also connected to the cable modem thence via ethernet to the LAN and other PCs. Don't know whether the TVs are on opposite sides of the house wiring. All told, I'd guess there's over 400 feet of coax & Cat-5 in that part of he picture.

The notebook was never intended to be 'earthed' per se. Now however, it finds itself grounded via the S-Video cable to the HDTV.

Toss in the complicating factor of wired and cordless phones which have cheap plug-in power supplies (we've had to reverse plug polarities on some of those to reduce 60 hz background noise on phone calls). The phones, in turn make it back into the RF cable grounding via Cox Cable's telephone voiceport. That's about 200 feet of Cat-2.

Gave my O'scope to the local middle school several years ago-- had too much stuff. Wish I had it now. Will make do with a VTVM.

Maybe a stick of dynamite would be best. <g>

I'll pick up the 15-pin RGB cable tomorrow meanwhile I'm taking the rest of a rainy afternoon off with a beer -- and watch golf.

On the other hand, Cox Cable offers an internal wiring plan for only a few bucks a month. :-)

Tks
--
pj
.