On Jun 24, 8:13*am, "N_Cook" wrote:
Mark Zacharias wrote in message

eb.com...





"gecko" wrote in message
...
This specifically relates to a Philips 28pw9527 television, but a
generic
response would be helpful, at least initially.

Over a period of about a year or so the black level on the blue gun has
gradually increased (my interpretation). *Initially it was noticeable
only
in dark scenes with studio scenes apparently unaffected but now there is
a
significant blue hue over all pictures. *The attached examples show a
normal programme and a screen showing "black" (the latter is *perhaps
exaggerated on the photo, and the moire is an artefact of the photo, but
the (flyback?) lines are real.

Can you explain what might cause this? *Is it likely to be terminal? *If
fixable, what is it likely to be? *This has been a great set capable of
a
fabulous picture and it would be a shame to lose it.

I have electronic experience with low-voltage devices but none with
tubes
or televisions. *I have the service manual, but can't really claim to
understand the circuits. *Any help - detailed or generic - would be
gratefully received.

I have searched throughhttp://www.repairfaq.org/samnew/tvfaq.htmand
other sites can't find symptoms which sound specifically like mine. *I
have found similar symptoms which apparently all point to a failing
tube,
but I am reluctant to believe that because only the blue gun is affected
on my set. Am I wrong?

Many thanks

There are adjustments for this, older sets use potentiometers, newer ones
set values of drive, cutoff etc in memory and are adjusted through the
"servicer menu", a hidden function accessed by a certain string of button
presses on the remote. Not given to consumers because there are so many
technical adjustments that would just mess up the set if messed with by
the
unknowledgeable.

Mark Z.

Swapping the drive for blue and red gun , say , will show if its a problem
with *the drive or the output stage.- Hide quoted text -

- Show quoted text -

That depends on how the set is set up. If three separate cathodes and
grids, maybe ok. If a common cathode for all three guns, also maybe
ok. But neither is a sure thing.