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Discussion Starter #1
Hello Icaillo, I have been reading through the 30+ pages about convergence problem with RPTV for about a week now and I could not find similar situation with my 1996 RCA P60756BA. It seems like a convergence problem but with a slight difference so I hope you can help me out.

First let me introduce myself, I have been playing with electronics since the 50's beginning with tube radio but sort of stop when transistors came about. I have also worked in a TV repair shop back then repaing many tube TV's. Nothing like what we had today. In the recent 20 years, I have fixed some but also damaged some too, but I am OK with soldering, replacing parts, fixing traces, etc. My other RCA 46" bought a few years before the P60 is still working like new because I had fixed the High voltage leakage near one of the CRT.

About 4 years ago, I took the time (3+ hours) to re-adjust the convergence throught the service menu and the controls on the congvergence gen board. I did a perfect job as everyone said this RCA show a better SD picture than my new Toshiba 72" DLP.

About a month ago, while the wife was watching her show, the TV suddendly streched the picture by about 20% diagonally on all 4 corners. the center portion of the screen seems unaffected. Where the corners stretches, the convergence are not good, the red green blue lines separated by about an inch. This lead me to believe something common to all 3 convergence amp.

While carefully remove the entire chassis from the cabinet, I did not see anything obvious to cause the problem - like burned resistors, discolored area, cracked traces etc. This TV does not have what was described in your thread (STK's) but instead there is a board (convergence amp) with 6 large heat sink and each heat sink has 4 large transistors mounted. There's a power supply board on the side supplying power to the convergence amp which output to the convergence generator board (where all the service adjustments are).

I am not sure if this picture streaching on all 4 corners have anything to do with convergence either. I am wondering if you have ever run into such problem with this model? Yes it is an older TV and not even HD but when working, everyone said it got some of the greatest picutre they've seen, I sure hate to throw this TV away. Please help if you can, Much thanks, max

PS: TV came with component diagrams, parts list etc. but all in a sheet of paper with tiny print that is very hard to read.
 

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These sets use discrete outputs, not ICs. Other than looking for coolant leaks or bad solder connections, these are not trivial repairs. These sets can be a challenge for even a seasoned TV tech. Not a good choice for a DIY project. Get the service documentation for this chassis if you plan to proceed, but do not expect this to be an easy repair. You could have a convergence problem or you could have a problem somewhere in the deflection, power supply, or pincushion circuits. You might want to find a tech who is very familiar with this chassis. It might be an easy and cheap repair for someone who fixed a lot of these, but for most of us they were not a joyful proposition.
 

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Discussion Starter #3 (Edited)
Thank you for your suggestions. After carefully removing most of the wires, plugs, etc. I observed the following:
- LM311N - used as Side Pin (what ever this means), there's a fair amount of liquid (dark brown color) at the bottom of this comparator chip. I tried my best to clean up and found Pin #6 (balance strobe) not connected to the board. It is very hard to see and I was using a mirro in the tight space. I am not sure it was like that from factory or the pin had corroded away?? I took the top and bottom picture. Hope I can post it here...

first photo you can almost see pin 6 corroded away
second and third photo was taken from the bottom of pin 6

question: what do they mean by Side Pin?

Cheers, max
 

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pin = pincushion, which is the curving at the sides and top of the image that occurs with no correction to the scanning. It is hard to tell from the quality of the images, but it looks like a collant leak. There is a sticky regarding leaks that might help. If there is damage to the circuit, it will need to be repaired, the board cleaned, and the leak repaired. This can be a messy and tricky job if you are not familiar with these problems. A tech who has done lots of them will have no trouble fixing it, but a DIYer often gets in over his head on these.
 

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Discussion Starter #5
pin = pincushion, which is the curving at the sides and top of the image that occurs with no correction to the scanning. It is hard to tell from the quality of the images, but it looks like a collant leak. There is a sticky regarding leaks that might help. If there is damage to the circuit, it will need to be repaired, the board cleaned, and the leak repaired. This can be a messy and tricky job if you are not familiar with these problems. A tech who has done lots of them will have no trouble fixing it, but a DIYer often gets in over his head on these.

Yes, the picture are not very good, I had to do a lot of tricks just to take those at that close range as I did not remove the circuit board completely. RCA did not make it easy for the board to be removed. I had to use another lense attached to the Zi8 camera for macro shots. Taking photo seems to be another challenge by itself but its fun.

I read a bit about coolant leak in your post but did not completely understand it. What component(s) would have coolant? I could not find (still have not figured out how to use search function) the other post regarding coolant leak so if you have a link, let me know.

The area surrounding the LM311N are clean and dry, the brown liquid I cleaned up is "only" at the bottom of the chip so I can not tell where the liquid is coming from. Looking at another bottom photo I took this morning, I can see there is definitely a pin (under the letter 'U") from the LM311N. I think I will try to clean up the hole and solder a wire through the hole to see if I can solder that wire to what's left of the pin next to the chip.

The only other thing I found this morning is there is another burned (carbon?) spot on the circuit board below a heat sink for Q4107 (+10.3V REG.) that is very close to a resistor (+33.7V run). I tried to scrape the burned board but it is not easy with the heat sink in the way. Had to figure out a way to stop the arcing.

With all these faults, it is amazing the TV still working albeit with slightly stretched corners...
 

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Discussion Starter #6
Just for confirmation, when I touch the tip of the iron on the bottom, the broken pin came off so there's definitely a pin.
Next I use a solder sucker to suck the hole clean and inserted a small wire throught the hole, solder the wire at the bottom and tried to solder the wire to the left over portion of the pin on the chip, not an easy thing to do as there are no tin on the top part of the pin. I had to use photo evidence to make sure that the solder took as my 62 year old eyes can not see clearly at the allowable angle. took about 60 shots to get the picture and still not clear enough...

from the large phot, I did accidentally touch the solder on the pin 7...
 

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Discussion Starter #7 (Edited)
I went out to pick up a set of dental pick, try to scrape the carbon arcing area clean. I am wondering if i should dap silicon sealant on that area? Looks like the arcing is between the bottom corner of the heat sink and the resistor.
 

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Discussion Starter #9
Time to put it together...

Convergence was where it was when I did the service adjustments few years ago, just a slight touch up on the customer's adjustments due to TV was turn 90 degree for a few days while doing the repair. Total of about 5 hours off and on for the repair, no parts was required aside from a small piece of wire and less than 1" of solder. I can declare this repair a success BUT, now the wifie is saying she just lost the chance to buy a new TV!
 

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Discussion Starter #10
The board needs to be cleaned carefully and thoroughly if there is coolant damage. If you don't, corrosion will continue.

http://www.hometheatershack.com/forums/diy-repair-maintenance/8019-crt-based-rptv-coolant-problems.html#post67460
Many thanks for these info, I cleaned the board as much as I could but not able to use alcohol or, for that matter washing the board due to the tight nature of all the surrounding parts. Removing this board is next to impossible. The TV is working good now, but I think what I will do in the next few days is to install a plastic shield above the LM311N IC and surrounding area so it there are more leaks coming down from the tube, it will flow away & to the bottom of the cabinet. I don't think it is worth the trouble of trying to fix the leak now that the TV is 15 years old.

I still have to deal with the wifie regarding buying a new TV :D:D:D
 

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Sorry, no stickies for dealing with the wife. Electronics is easy by comparison. If I had answers to those kinds of problems, I would not be giving them away.:heehee:
 

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Discussion Starter #12
well so far so good after this many days, TV still work like new BUT, the wife want a new TV anyway. I got her a sony 46 EX500 from costco for a bit over $1,200 (all inclusive). That amount shocked her so she said take it back.
 

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Discussion Starter #13
WoW!!! a year later and the TV is still working the way it should be... We tried to give it away but no one want it so wife is still using it.

- - - Now for our bedroom, we got a new LG 47" LED for the price of a 47" LCD from Costco, yep they pile the wrong product on the pallet and happily took the lost when we bought it.

Cheers, max
 
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