Funny repeat problem with a 60 inch RCA PTK195AC (model P60812BL)

[[email protected]]

This is a continuing saga of a 60 inch rear projection RCA TV. It has
a chassis number of
PTK195AC and is model P60812BL. I have now had a repair technician
over and it worked like a charm while he was here and for a couple of
hours after he left. Then it returned to the absolutely black picture
it had when the problem first surfaced a few days ago. The repair
technician feels he should change the EPROM. Can an EPROM problem
result in NO output from a projection tube?

This is the sequence of events.

The other day one minute it was working perfectly (as it has for 8
years). All of a sudden I walked into the room and the screen is black
(none of the projection tubes are putting out any light).
Turning it off, using the DVD and many other attempts to get a picture
failed. I let it stay off for a while, then turned it on. It would have
a
picture for a short time that looked like an old 60's horizontal hold
problem with a partial, shrunken picture. After a while the picture
would be stable enough to be able to read letters, but totally
distorted. I was afraid to leave it on long figuring I might stress
the conditon. I called a repair technician and he came over today.

The repair technician went into the service mode of the TV and changed
a number of parameters stored in the EPROM and finally got it looking
as good a new. He also used an external alignment generator and the
grid looked straight and proper. Colors were true and bright. As I
said, this lasted about a couple of hours after he left and then the
screen went black (non of the projection tubes are generating any
output) which is exactly the condition that happened when the problem
first started. The filaments in the projection tubes glow and the
sound and power-on sequence is just as it should be. So far I have
not been able to get any type of picture back. I tried to get into a
service mode per the instructions to push the menu power and +vol
button. I have no picture and that did not give me one to be able to
see any setup procedure. Again, would a bad EPROM result in NO output
from the projection tubes?


Anyone have any ideas where to start?

 

[Asimov]

"[email protected]" bravely wrote to "All" (03 Jan 06 18:26:35)
--- on the heady topic of "Funny repeat problem with a 60 inch RCA PTK195AC
(model P60812BL)"

eg> From: [email protected]
eg> Xref: core-easynews sci.electronics.repair:353850

eg> This is a continuing saga of a 60 inch rear projection RCA TV. It has
eg> a chassis number of
eg> PTK195AC and is model P60812BL. I have now had a repair technician
eg> over and it worked like a charm while he was here and for a couple of
eg> hours after he left. Then it returned to the absolutely black picture
eg> it had when the problem first surfaced a few days ago. The repair
eg> technician feels he should change the EPROM. Can an EPROM problem
eg> result in NO output from a projection tube?

eg> This is the sequence of events.

eg> The other day one minute it was working perfectly (as it has for 8
eg> years). All of a sudden I walked into the room and the screen is
eg> black (none of the projection tubes are putting out any light).
eg> Turning it off, using the DVD and many other attempts to get a picture
eg> failed. I let it stay off for a while, then turned it on. It would
eg> have a
eg> picture for a short time that looked like an old 60's horizontal hold
eg> problem with a partial, shrunken picture. After a while the picture
eg> would be stable enough to be able to read letters, but totally
eg> distorted. I was afraid to leave it on long figuring I might stress
eg> the conditon. I called a repair technician and he came over today.

eg> The repair technician went into the service mode of the TV and changed
eg> a number of parameters stored in the EPROM and finally got it looking
eg> as good a new. He also used an external alignment generator and the
eg> grid looked straight and proper. Colors were true and bright. As I
eg> said, this lasted about a couple of hours after he left and then the
eg> screen went black (non of the projection tubes are generating any
eg> output) which is exactly the condition that happened when the problem
eg> first started. The filaments in the projection tubes glow and the
eg> sound and power-on sequence is just as it should be. So far I have
eg> not been able to get any type of picture back. I tried to get into a
eg> service mode per the instructions to push the menu power and +vol
eg> button. I have no picture and that did not give me one to be able to
eg> see any setup procedure. Again, would a bad EPROM result in NO
eg> output from the projection tubes?


eg> Anyone have any ideas where to start?


Could be the tuner shield ground problem where the solder cracks along
the edge of the PCB. This has many different symptoms. Some people
were being waken in the middle of the night with the TV blasting at
full volume on a blank channel. Some had the sound muted permanently.
For some the tv would turn itself off. They thought their tv was
possessed. Others had the HOT fail repeatedly. Still others had a
corrupted eprom. There is a FAQ for the GE/RCA/Thompson bad tuner
shield ground problem. Good luck.

A*s*i*m*o*v

.... This message transmitted on 100% recycled photons.

 

[Kev]

Try Replacing RN14501 in frame section.

 

[John-Del]

Sounds like a coolant leak. Look at the front of the signal board for
any clear liquid. I had several that caused intermittent picture.

John

 

[Leonard Caillouet]

I'd be looking for a coolant leak. About half of the problems that we have
seen on the 195 chassis have been related to coolant on the boards. It can
be hard to find but the first thing to look for is a dark goo on top of the
board.

Leonard

 

[Leonard Caillouet]

Also look around the red connector at the front of the board on the right.

Leonard

 

[[email protected]]

Well, I thought you-all were pulling my leg about coolant. What is the
origin of this coolant? I looked around on top of the boards (and my
service repair guy also had the chassis out and did not mention
coolant--but I will ask him about that) and I see only a light dust
over the surface of the boards (chassis is quite clean for something
not touched in 8 years). Since I have the service manual, could you
give me a number/letter coordinate to locate this possible leak? The
boards are labeled Main Circuit Board, Convergence Circuit Board, etc.


I hear your suggestions, but since the repair technician is headed
toward replacing the EPROM, I would like your evaluation as to whether
that makes sense or not. By the way, apparently there are TWO EPROMS
from what I am reading in the service manual.

 

[[email protected]]

Sounds like a coolant leak. Look at the front of the signal board for
any clear liquid. I had several that caused intermittent picture.

John

I agree, it really sounds like a simple case of crt coolant leaking
somewhere on a circuit board. Trying to tell someone a specific
location to look is not going to help as the coolant could be anywhere.
It will take a good visual inspection of the boards.

A second possibility is some glue under a surface mount capacitor could
have gone conductive on the clock or data lines. Another hard one to
find for someone who has not had to sit and troubleshoot the light box
for weeks in the shop.

An eeprom is 99% sure not the problems here.

David

 

[James Sweet]

Well, I thought you-all were pulling my leg about coolant. What is the
origin of this coolant? I looked around on top of the boards (and my
service repair guy also had the chassis out and did not mention
coolant--but I will ask him about that) and I see only a light dust
over the surface of the boards (chassis is quite clean for something
not touched in 8 years). Since I have the service manual, could you
give me a number/letter coordinate to locate this possible leak? The
boards are labeled Main Circuit Board, Convergence Circuit Board, etc.

The coolant is glycol based and is used between the face of the
projection CRTs and the optics. It conducts heat away from the tubes to
a heatsink around the rim where the lense assembly bolts on. Very old
projection sets were air cooled, but just about anything made in the
last 20 years will be liquid cooled.

 

[[email protected]]

I looked very carefully in the area below the CRT to optic interface
and then all over the boards. I also ran my finger under and around
the plastic cover area over the projection tubes where I would think
there would be residue if there was a leak. I then looked over both
the main boards. I sure don't think there is a leak. The boards look
very clean except a very slight dust due to the years of just sitting
around.

Again, do you think that the EPROM could cause a complete lack of the
projection tubes putting out any light? The only evidence that the TV
is working is the regular starting sequence, normal sound and a glow of
the filiments from the projection tubes.

 

[[email protected]]

Again, do you think that the EPROM could cause a complete lack of the
projection tubes putting out any light? The only evidence that the TV
is working is the regular starting sequence, normal sound and a glow of
the filiments from the projection tubes.

And again, 99% sure the EEprom is NOT the cause of the problem. The
technician needs to take the light box into the shop where it can be
properly troubleshot and repaired. If the tech still thinks it is the
eeprom and wants to just throw parts at the set, I would suggest you
ask if the servicer has a bench tech who can work on the set when the
light box is taken in. I do hope the servicer was RCA authorized and
attended all the factory training.

The ctc195 series is a PIA to troubleshoot and it is prone to lots of
intermittent issues. There are also multiple service bulletins that
need to be checked for the specific set to see what serial number range
it falls under.

99% of the time an eeprom looking problem on that chassis winds up
being glue that has become conductive underneath a surface mount
component on the clock or data lines. I have repaired several hundred
of that chassis with this very specific problem over the last 6 or so
years.

 

[[email protected]]

Ohhh boy. I hope the technician is right and we are wrong. Just for
reference, the Service # is P60812BLLG2. The number on the metal tag
on the main board is CTC195A JR47344C9D. The # on the digital
convergence board is PTK195AC 0 7355K2D
A number below that (which looks like a serial number) is
59835735521092RWB-TCE.

The technician said that the service number was the important number
for ordering the EPROM.

Which of these numbers have significance to any of you?

 

[kip]

Its not an EPROM problem...
Get somebody in that has chipper checker and get IT tested.

 

[[email protected]]

The so called technician hasn't a clue and is guessing. You need to
call someone out while the set is non-functional to hook up the
computer interface and read any error codes and ping the data bus
connected devices in the set.

Or, you can waste your time and money having the same technician keep
guessing on your set until it is beyond economical repair.

 

[[email protected]]

Last night I turned on the TV --still no output from projection tubes
-- and rapidly pluged in the AC plug and disconnected it. Don't ask me
why I did it, I guess I thought I might simulate the original cause?
Anyway, the projection tubes "flashed" on for a split second, so it
looks like they are just "turned off" somehow. The technician told me
that the projection picture tube filiments are powered from the
horizontal circuit, so that circuit must be working since the filiments
are glowing.

We are still waiting for the EPROM to come in. I have mentioned the
things you-all have talked about, and he does not discount them, so
that is good. His rationail that the EPROM is the problem is that it
was corrupted when he first looked at it. It is in the state it was
when the original problem occurred before it "kind of" came out of it
and present enough of a picture that he was able to see enough of the
picture to get it working normally.

Is there a major problem in changing the EPROM and that NOT being the
primary problem? Would that create a larger problem in getting the
parameters back? Does he have to somehow download the old EPROM
parameters into the new EPROM? Does the new EPROM come loaded with
some "default" parameters so the TV is able to provide a picture if the
EPROM is the problem?

Can and should he bring out the chipper checker when he comes?

 

[[email protected]]

I started another thread since I thought this would continue. In it I
wrote

Today the technician came and changed the EPROM and as you-all pretty
well told me, it was not the EPROM. After I mentioned the coolent
problem, he homed in on that and found a couple of drops and after that

pretty well gave up saying that the board was as good as gone. Since
now the TV is so much garbage unless I find an answer to this, I tore
into it tonight.

Well, to make a long story short, what I did fixed it (at least for
now). You can read about the details below:

Yes, there is a drop or two (and a drop or 2 is not
an exaggeration). There is a drop or two on a wire and some evidence
in of it (a slight film on the top surface of the components) in the
vertical deflection section on the right rear side of the main board).
There is NO evidence that any corrosion has started anywhere I can see
on the main board. I took the main board out of the plastic tray and
examined both sides with high power magnifiers and the circuitry looks
clean and bright.


Very interesting finding, however. The large chip behind the tuner
(UT16201) was soldered in by someone and there is a lot of solder flux
around the chip. It appears that their was some circuit damage when it

was replaced. Now, I have never had a repair person in to look at the
TV, so this must have happened at the factory (TV bought in June of
1998).


Anyway, I am cleaning the underside of the board carefully with some
circuit board cleaner in the area of the UT16201, the EPROM and the
vertical deflection section as well as the Micro (U13101) in the rear
of the main circuit board. I assume that the possibility of conductive

glue mentioned around the clock and data lines described in the
previous postings would be in this area (described as the service micro

on the board).


I will now reassemble the TV and try it out. If what I have done does
not demonstrate improvement, do you-all think it wise to remove the
chassis and find a knowledgeable repair person to look at it? How do I

find THAT person? This outfit I used was listed as a factory
authorized repair service.


Again, for reference, the service # is P60812BLLG2. The number on the
metal tag
on the main board is CTC195A JR47344C9D. The # on the digital
convergence board is PTK195AC 0 7355K2D
A number below that (which looks like a serial number) is
59835735521092RWB-TCE.


Thanks again everyone for your comments and suggestions.

 

[[email protected]]

Its now nearly a month later and my RCA 60" TV is still working. The
picture is great. I think the convergence could use some improvement
in the lower left corner, but not having a color/bar/dot generator and
not wanting to push my luck, I am very happy with it right now. The
technician sent me $150 of the $250 back and so I guess I learned some
things and hopefully have a working TV for a few years until I have to
go to HDTV.