Thread: Philips G22K550
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Old 16th Feb 2007, 7:59 pm   #9
ekcopyephilips's Avatar
Join Date: Dec 2006
Location: Norwich, Norfolk, UK.
Posts: 398
Default Re: Philips G22K550

Hi Guys

It did indeed have a very bad purity error, caused by not having its posistor fitted. (i took the pics before i fitted it ). The purity error has now gone.

Mike, I wasnt sure if the decoder was off alignment or I was confusing myself.
I recently purchased a Philips PM 5508 pattern generator off a well known auction site. Its an old unit and i was very suprised to also receive the original instruction manual, which has colour photos in it of the test cards and what they look like in normal and fault conditions. When I chose to display the 'Phase' pattern, the TV showed what the book described as a decoder alignment error.

The pattern concised of four vertical bars, the upper half of the bars encoded to the PAL alternating standard, whilst the lower part contains colour infomation only on every "positive" PAL line. The latter means that only those lines with a burst phase of 135 degrees carry colour information. The burst is the normal PAL alternating burst for the entire pattern. To ensure the same colour impression of the upper and lower parts of the pattern, the upper part is generated with only half the chroma amplitude.

The manual then went on to say that, one should check the upper and lower parts of the pattern produce the same colours during the same vertical bars. If the colours differ, the chroma demodulators are not adjusted correctly.............phew

Sorry if i went a bit off topic there, but thats why i was getting interested in decoder alignment

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