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Posted by Gary on 08/07/07 00:03
<Josephine_Blevins@remailer.metacolo.com> wrote in message
news:3351b19d1d8bbc514aaaa8ebed62bdec@remailer.metacolo.com...
> The Philips Audio-Video automatic selector (switch) Model # PH61153 may
> cause a certain kind of video noise problem. This unit contains active
> electronics and is powered by an AC Adaptor which converts 120 vac to 12
> vdc to power the selector switch. The switch is very convenient in use,
> much more so than an alternative manual switch that is totally passive and
> may be immune to the problem observed.
>
> The video noise occurs on any of the three inputs and is visible on the
> svhs output; I did not test the composite video output for noise.
>
> The video noise appears as faint light horizontal bands which slowly move
> up the screen, repeating every few seconds. If you have this problem, you
> can isolate it to the selector by bypassing it temporarily. If the
> problem
> goes away, it is generated by the selector. I have determined the problem
> to be a.c. ripple riding on the d.c. from the AC Adaptor. There is a fix.
>
> All that is necessary to complete clean up the video is additional
> capacitance on the power supply. The easiest way to do this is to insert
> a
> large capacitor in parallel between the AC Adaptor and the d.c. input of
> the selector switch. Here is a parts list:
>
> Capacitor: electrolytic, 8400 uf 40 v rating Sprague type 36 D or similar
> 1 required
> Power jack: 5.5mm o.d., 2.1mm i.d. (Radio Shack 274-1563) 1 required
> Power plug: 5.5mm od., 2.1mm i.d. (Radio Shack 274-1569) 1 required
> Ring terminal: for #10 screw, 18-20 ga. wire, solder type preferred 2
> required
> Zip cord: #22ga, length 6' or as required
> Misc. PVC electrical tape, heat shrink (optional), rosin core solder,
> soldering iron (20 to 40 w)
>
> Assemble the wiring such that the power supply connects via the power jack
> and the power plug goes directly to the selector switch. Tape over all
> exposed wiring and terminals.
>
> The AC Adaptor will now supply pure d.c. to the selector switch and all
> switch-generated video noise will disappear. You may feel free to repost
> this advice on any applicable newsgroup or web forum.
>
>
You could try central earthing first. Symptom described s known as a HUM BAR
and is more often than not an earth problem
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