On Sun, 23 Dec 2007 13:18:12 -0500, Meat Plow
wrote:
On Sun, 23 Dec 2007 17:32:52 +0000, D&K wrote:
On Sun, 23 Dec 2007 12:00:48 -0500, Meat Plow
wrote:
On Sun, 23 Dec 2007 15:22:52 +0000, D&K wrote:
I have a Sharp RPTV, model # 61R-WP5H, 61", about 6 years old.
For the past 6 months or so, it will work for random lengths of time.
Sometimes 6 hours, sometimes 3 weeks. Eventually, the image will
collapse & disappear into to bottom center of the screen, and the
audio disappears about 2 seconds later. The power LED shuts off & the
LED next to it (status?) begins blinking twice every 1.4 seconds.
Unplugging the set for awhile will make it come back, again for a
random amount of time. Eventually it happens again. Lately it's gotten
worse, lasting no more than 30 minutes before shutdown.
According to the service manual, 2 blinks every 1.4 seconds indicates
that the "vertical output protector circuit" is not detecting any
vertical output. Without this protection, the image would collapse
into a single horizontal line across the screen.
Next to that, it shows a diagram of " IC501 " monitoring the vertical
output as a 14V signal. The parts list in the back describes
everything beginning with "IC" as an integrated circuit in the form of
a chip or a voltage regulator. So my goal was to locate " IC501 " and
find a loose solder joint somewhere in it's vicinity.
Problem is, " IC501 " doesn't seem to exist. It's nowhere on the
indicated circuit board, nowhere in any of the schematics or PCB
drawings, and nowhere in the replacement parts list. I've found other
IC's with similar numbers (IC601, IC6501) but all are described as
something different on the schematics.
The printed circuits on the board in question are large enough for me
to repair with the soldering equipment I have. But it's a big board,
and I just want to narrow down the location. Putting the PCB
assemblies back into the set & reconnecting everything in order to
test takes about a half hour, and I'd hate to have to do it more than
once or twice.
Any direction would be appreciated.
Component grid numbers are usually grouped by circuit function. I say
usually because this is my experience, others may or may not agree.
What I mean by grouping is that an IC in the vertical may start with
IC5xxx, horzontal IC6xxx and so on. Same with say resistors (R5xxx, R6xxx)
Things to check: Make sure you have the exact service literature.
Try to find other ICs or components grouped together with the 5xxx number.
That's about it for me 
I thought that might be the case. I've found the 2 zener diodes also
shown in the diagram, but the mentioned IC is nowhere around. I also
found what appeared to be a loose solder joint on a capacitor nearby,
and resoldered it. I just want to exhaust any possibilities before
reassembling everything.
Thank you for your help.
You're welcome. Hope you resolve the problem and I don't blame you for not
wanting to leave no stones unturned. If you've identified where the
vertical components reside a good scan underneath for bad solder joints
is a great idea. I've done this countless times even using a stereo
magnifying visor.
Resoldering that joint didn't work, it still shuts down. I did manage
to identify the vertical IC, but there's not a bad joint anywhere near
it.
So, what can cause the vertical signal to just randomly stop? I'm not
sure what else to try here.