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

" snipped-for-privacy@yahoo.com" 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: snipped-for-privacy@yahoo.com 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.

Try Replacing RN14501 in frame section.

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'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

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

Leonard

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.

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

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.

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.

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.

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?

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

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.

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?

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.

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.