Were dealing with an early 90's Proscan TV.
About two months ago my TV started to display a solid white backgroundwith no retrace lines. The sound works fine along with all menus and tvfeatures. Ex: I can change the channels and the channel number will popup in the upper right hand corner in full color or the menu system willdisplay in the spectrum of colors as intended. Sometimes the tv will
lose the white screen and display the correct image, however this is
rare(It works for minutes, days, or weeks at a time on rare occasions).
PIP works well and it displays the seperate images PIP is supposed to
look, however when PIP comes on the background other than PIP turns
from white to a medium gray. The Svideo(90) and other inputs are also
white.
The TV is less likely to display full color when its been sitting and
its cold. There is no smell or visible trace of burnt components.
Anyone have any ideas?
If the PIP works try doing a swap. If the picture come on, your problems in the PIP module. Let us know how you made out or if you need more assistance.
By swap I assumed that you wanted to turn PIP on and swap the channels between the two. When i did i heard the channel get a little quieter like it was changing the channel but nothing visible happens.
When i pressed the reset button on my controller... the TV instead of having a gray background when the tv was on it was stark black. That made me question my previous setup of the brightness and contrast. Alas, when i try to set the contrast and brightness to make the PIP background gray again it doenst get near the depth.
The swap did nothing, and the reset button changed the brightness and contrast. When i turned the TV on this morning it worked for about 3 seconds right after turn on. Then it flickered picture, white, picture, white, then off.
But reading the rest, it sound as though your jungle ic has gone south
or going that way
Im going to test around and see what i can come up with on this one. Anyone have any other ideas or can you compoud on this one?
Does this sound about right?
"Other than power supply problems, this is the second most common circuit to
give people problems on our sets made in the last 5 years. If you have high
voltage and vertical deflection (as you indicated) the unit is probably in
what we term as 'IK blanking'.
The jungle IC sends a 60us pulse in the vertical blanking area in order to
monitor CRT cathode current, thus maintaining white balance. Each color drive
output has its own pulse in this area (Red=line 17, Green=line 18, and
Blue=line 19. These pulses are them matrixed and returned to the jungle IC to
be monitored. If one or more of the pulses does not return (or is very low)
the jungle IC will keep the video off. Bad video drivers, weak CRT cathodes or
faulty IK pulse return circuits will cause this symptom".
Here's how to find the cause: Even though the video is off, the Jungle IC is
sending the pulses to the CRT board. Measure each of the cathodes with a
scope. At vertical rate you should see a 60us pulse at each cathode about
20-50 volts in amplitude. What we're looking for is one of the cathodes to
either have an extremely large pulse (in comparison to the other two) at about
150 Vp-p or having no pulse at all".
If one cathode has no pulse, troubleshoot the driver circuitry for that color.
If one cathode has a very large pulse, the cathode is weak or the return
pulse is not making it back to the Jungle IC. To tell if the CRT is bad, turn
up the screen control and see if you get a raster with one of the primary
colors missing. It should be the color that you saw the large pulse on. If the
raster is white or is slightly dominant in one of the primary colors, the CRT
is probably OK. Troubleshoot the IK return buffer transistor and associated
components for that driver.
If all 3 cathodes have a large pulse (150VPP) Then check the following:
1. The IK buffer transistor which is sending the combined pulses out of the
CRT board (all three must be present here and at least 700mvpp).
2. The screen control is turned too low.
3. G1-G2 short or leakage. this will be evident by G2 voltage dropping
drastically while the CRT board is mounted on the tube and raising when
removed."
-- end quote --
Maybe the boosted B voltage is low, What is the chassis number? Starts with CTC
From my notes I have found that the delay line DL2701 was bad, Q2906,C1406,U8501, and u2601. These are parts that have been replaced in the CTC169 chassis for a white picture(no video) Good Luck