Re: blue hue
Mark Zacharias
news:OIGdndNRdNfLyp7T...@bt.com...
> 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 through http://www.repairfaq.org/samnew/tvfaq.htm and
> 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.
William Sommerwerck
>> 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).
The most-likely explanation is that the bias on the blue gun is drifting
"upward", so the darker areas of the picture are turning blue. You don't
need to understand the circuits to fix the problem. (I could make a
wisecrack, but I won't.)
This is easily fixable, if the set has potentiometers on the back. You're
looking for the one marked "blue screen", or something similar. You need to
turn it down (CCW, presumably) a bit.
Mark pointed out that some sets use a software-based system, which requires
gaining access to the service menu. Regardless, browse the manual to find
the "setup" section.
N_Cook
news:4e047d5f$0$27993$c3e8da3$3863...@news.astraweb.com...
Swapping the drive for blue and red gun , say , will show if its a problem
with the drive or the output stage.
hrho...@att.net
> Mark Zacharias <mark_zachar...@sbcglobal.net> wrote in message
>
> news:4e047d5f$0$27993$c3e8da3$3863...@news.astraweb.com...
>
>
>
>
>
> > "gecko" <m...@f2s.com> wrote in message
>
> - 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.
William Sommerwerck
We have given the OP the basic information he needs to get started. (I would
also recommend he read a book on color TV operation and servicing.) He needs
to look through the service manual for information about setting up the
set's "tracking". Once he's done that, and perhaps fiddled a bit more with
the set, he can come back and ask more questions.
Jeff Urban
This is a Phillips and if it is a CRT based RPTV it has contaminated
coolant. Look at the bright areas of the picture, are they yellow ? I
bet a case of beer they are.
I've seen worse, one said to pierce the anode caps to discharge the HV
here in SER, geez, that would make for $200 additional work. Talk
about not knowing WTF one is doing. But this is not as bad.
Anyway, look in the lens, THE LENS. It will be all hazy. Take it
apart, clean it up and change the fluid. I have done hundreds of them.
And more in other brands. But NAPs get it in the blue and green
mainly. If you can't get the fluid anywhere else, get it from MCM. We
were getting it for about a third of what they charge by we bought a
hell of alot of it.
It's caused because they leave an air gap, to help prevent leakage,
which happens from the gradual expansion of the fluid over time. It
doesn't work because they still leak at times. Plus I think their
coolant is not the best.
If you attempt to service an RPTV that is CRT based and don't get the
idea to look straight into the lens(es) when you see this, do
something else.
J
gecko
replies. It seems I have been responding directly rather than to the group.
I have been through the extensive service menu options and found the
following settings (with service manual instructions):
Cathode (set to 15 for all picture tubes)
Colour Temperature (select Cool/Normal/Warm) [currently set to Warm]
Red, Green, Blue (set according to table for colour temperature) [they are
within specified range]
Red BL offset, Green BL offset (defaults 7, 6)
So I guess I could tweak the last two upwards? But relative to what? I
can't see an overall black level setting. Should I adjust these up and the
brightness down, perhaps?
More importantly, Is this the best course of action? My gut feeling is that
the blue level is so far out, that some component (hopefully a resistor)
must be failing? I have now had a chance to look inside and think I'm
probably out of my depth. Those circuit boards are packed and double-sided.
If there's a faulty surface mount I don't rate my chances of finding it.
The microprocessor has no faults and no faulty components in its fault log.
So I'm on the verge of giving up on it, but would welcome your further
thoughts.
P.S. again to those who haven't seen my previous replies this is a 28"
conventional crt, not a projector.
"N_Cook" <div...@tcp.co.uk> wrote in message
news:iu22f2$ufr$1...@dont-email.me...
William Sommerwerck
I sincerely feel you should stop at this point. You are in way, way over
your head. Most of the people in this group would have little trouble
adjusting the set in-person -- trying to explain it via e-mail to someone
who doesn't understand the basic elements of color-TV adjustment would be
extremely difficult. You need someone to step through this with you.
If you like, call me over the weekend and I'll try to walk you through this.
I just realized you're not in the States. So much for that.
Geoffrey S. Mendelson
> I just realized you're not in the States. So much for that.
Besides the time difference, what's that matter? Most people outside the US
have some way of calling the US, often for less than they pay for local
calls.
Or possibly SKYPE? For example, my sons talk to people on every
continient, except Antartica, every day using SKYPE. He and his younger
brother simply have no concept of a long distance call.
Geoff.
--
Geoffrey S. Mendelson N3OWJ/4X1GM
Making your enemy reliant on software you support is the best revenge.
William Sommerwerck
news:slrnj163c...@cable.mendelson.com...
> William Sommerwerck wrote:
>> I just realized you're not in the States. So much for that.
> Besides the time difference, what's that matter? Most people outside
> the US have some way of calling the US, often for less than they pay
> for local calls.
> Or possibly SKYPE? For example, my sons talk to people on every
> continient, except Antartica, every day using SKYPE. He and his
> younger brother simply have no concept of a long distance call.
Fine with me. If the OP wants me to help, he can call me any time after 3AM
PDT (yes, AM) on Saturday or Sunday, and we'll see if we can figure this
out. 425-891-7082
gecko
Thank you William for your generous offer. I won't take you up on it right
now because, I think there was a level of truth in your previous post. I
thought I had the basics in principles (although no more than that), but
having taken the back off I think maybe I don't. I don't wish to occupy
your valuable time. It is generous enough that you would all help me this
way.
I may have a further inspection and if I feel I can find my way around the
set maybe I could take advantage of some more pointers at that time?
But many thanks again, it's very much appreciated.
Perhaps I could ask for a little clarification though: I am happy with the
concept of setting an overall black level, and then tweaking the Red and
Green as offsets from that. But although there are menu controls for R & G
offsets, there doesn't seem to be an explicit one for overall black level.
Would that be called something else, or adjusted in some other way, such as
a physical control. Or am I way off the mark?
"William Sommerwerck" <grizzle...@comcast.net> wrote in message
news:iuvabd$v0a$2...@dont-email.me...
William Sommerwerck
> Thank you William for your generous offer. I won't take you up on it
right
> now because, I think there was a level of truth in your previous post. I
> thought I had the basics in principles (although no more than that), but
> having taken the back off I think maybe I don't. I don't wish to occupy
> your valuable time. It is generous enough that you would all help me this
> way.
My whole life is valueless. Spending an hour with you Saturday morning is no
big deal.
> I may have a further inspection and if I feel I can find my way around the
> set maybe I could take advantage of some more pointers at that time?
Call me when you're ready.
> Perhaps I could ask for a little clarification though: I am happy with the
> concept of setting an overall black level, and then tweaking the Red and
> Green as offsets from that.
Error. Error. Error. You do not set an overall black level, per se. You turn
the Brightness control down (almost) all the way, THEN adjust R, G, and B
until the beams just cut off.
Look on the back (or inside) for a Service switch. When you find it, try
moving it.