Dear Person:
I have an RCA P46731AT with a PTK169pga board..The pix is curved on both sides (inward)...There is a small board mounted by the flyback that has 3 adjustments on it...
One is "Horiz Width" & it works perfectly...
The 2nd is "Horiz Phase / Trap" that gives little effect...
The 3rd is the "Pin Amp Adjust" (R-4805) that has NO effect...
There are only 2 lytic caps on that board & I've checked them ( ESR & value)...Both checked OK...
I do NOT have the exact schematic & badly need one...
However , the voltage at the"Pin Out" transistor collector will adjust to a max of 18 volts using the "width" control...
There are 2 IC's on that board ( one is a 8 pin & the other has 16 pins )
My schematic has only an 8 pin IC which is NOT correct....
I would APPRECIATE it VERY much if a TV tech would reply to this post with some help as to the cause of this problem OR the means / location of a schematic / service manual ( Hopefully FREE )....
Thank you VERY , VERY much in advance for your anticipated help....
Ron.M....
If that board checks OK then suspect C401 - C402 - C403 they are mylar caps next to the horizontal output transistor mount on the heat sink marked Q401 . These tend to bulge at the sides . If C402 is defective also suspect CR402 it tends to short if C402 is bad . One other possible short would be Q802 . Also the marks i gave you are how they are listed the on the board . On a schematic these would be listed with four digits such as C4401 or Q4802 . Hope this will get your problem solved but i have no manuel . James
jsf2323 (James): 1st, Thanks for your reply....
I went for the jugular & checked both C4401 & C4402 with a good cap checker & they appear to be OK..(also no bulges)...I also checked CR4401 & CR4402...They also checked OK...I did not check C4403...I will check it...
Since I'm getting a max of 18 volts on the collector of Q4802 & I can vary it useing the width adjust ,I don't think it's shorted out.... I pretty much ruled those parts out...The problem has to do with the circuitry associated with R4805 "pin amp" adjustment...I suspect that a pulse from the vertical circuit is not getting thru properly...Could be from the Vertical output or one of the IC's on the small board..I THINK that U4801 is OK since it drives Q4802 & the width control is directly tied to the IC input...It's the other IC that MAY be a problem..I am NOT sure that that little board is OK...A schematic for PTK169pga would certainly be a HUGE help..
FYI: I'm a retired TV tech (45 years in it) & it's nice to talk to someone who knows a thing or two about TV's...
jsf2323: Thank you VERY much for your help..It IS appreciated...
Ok here are some voltages for you . Q4803 16v e - 15.4 b - 10.6 c . Q4802 13.7 c - .46 b - grnd e U4801 pin 1 & 4 (ground) 2 (4.46) 3 (4.51) 5 & 6 (24.7) 7 (.46) 8 (26) . Also here are some notes i have of this model with your same type of problem . Check C4814 if reads 30K ohms replace . If Q4802 is shorted suspect C4802 . Check solder joint of R4818 not thru the board . Check R4817 should be 270K if it increases replace . Also check C4801 . Check R4817 if it is opened . Check Q4802 out of circuit . Check C4812 for changed value . Check cr4805 the voltage should be 4.5v suppling pin 3 of U4801 if 10v replace diode (zener) . Check L4803 if opened or impedance has changed . Also make sure of CR4402 and CR4401 and make the value has not decreased or increase , these are most common . And if one or both are bad replace C4402 . If all else fails suspect U4801 . Also note some of these parts may not be on your set as these RCA and GE chassis vary so much . Good luck , James
If that board checks OK then suspect C401 - C402 - C403 they are mylar caps next to the horizontal output transistor mount on the heat sink marked Q401 . These tend to bulge at the sides . If C402 is defective also suspect CR402 it tends to short if C402 is bad . One other possible short would be Q802 . Also the marks i gave you are how they are listed the on the board . On a schematic these would be listed with four digits such as C4401 or Q4802 . Hope this will get your problem solved but i have no manuel . James
jsf2323 (James): 1st, Thanks for your reply....
I went for the jugular & checked both C4401 & C4402 with a good cap checker & they appear to be OK..(also no bulges)...I also checked CR4401 & CR4402...They also checked OK...I did not check C4403...I will check it...
Since I'm getting a max of 18 volts on the collector of Q4802 & I can vary it useing the width adjust ,I don't think it's shorted out.... I pretty much ruled those parts out...The problem has to do with the circuitry associated with R4805 "pin amp" adjustment...I suspect that a pulse from the vertical circuit is not getting thru properly...Could be from the Vertical output or one of the IC's on the small board..I THINK that U4801 is OK since it drives Q4802 & the width control is directly tied to the IC input...It's the other IC that MAY be a problem..I am NOT sure that that little board is OK...A schematic for PTK169pga would certainly be a HUGE help..
FYI: I'm a retired TV tech (45 years in it) & it's nice to talk to someone who knows a thing or two about TV's...
jsf2323: Thank you VERY much for your help..It IS appreciated...
Ok here are some voltages for you . Q4803 16v e - 15.4 b - 10.6 c . Q4802 13.7 c - .46 b - grnd e U4801 pin 1 & 4 (ground) 2 (4.46) 3 (4.51) 5 & 6 (24.7) 7 (.46) 8 (26) . Also here are some notes i have of this model with your same type of problem . Check C4814 if reads 30K ohms replace . If Q4802 is shorted suspect C4802 . Check solder joint of R4818 not thru the board . Check R4817 should be 270K if it increases replace . Also check C4801 . Check R4817 if it is opened . Check Q4802 out of circuit . Check C4812 for changed value . Check cr4805 the voltage should be 4.5v suppling pin 3 of U4801 if 10v replace diode (zener) . Check L4803 if opened or impedance has changed . Also make sure of CR4402 and CR4401 and make the value has not decreased or increase , these are most common . And if one or both are bad replace C4402 . If all else fails suspect U4801 . Also note some of these parts may not be on your set as these RCA and GE chassis vary so much . Good luck , James
jsf2323:
I spent the day looking for a schematic for this set...( I have a VERY slow & old computer )
I found a link on another forum for a RCA P46732 which is only one # away from mine...
It took me to a site that has a 15 part RAR file...Each file is about 1 megabyte or more...That took awhile...After I downloaded all 15 files , I tried to open them with a 7-Zip program I have on my computer...Wouldn't open the file....Back to "Google" where I found Jzip (5.36MB's)...Downloaded & that took awhile...It opened the 15 part file OK...BUT , After opening that file (181 pages) & going thru it , the dam file does NOT have the info I need...
I tried to check out some of the info you so graciously provided , & could not find some of the parts you listed....I have to work a half shift early tomorrow , so I will finish that up tomorrow or Saturday...
I will post when I get that done & let you know the results....
MANY THANKS for your detailed & informative reply....
Dear jsf2323 & others:..SORRY about the delay....
...THANK GOD !!!...That said....
My good friend & landlord was suddenly hospitalized last Thurs nite....His skin turned yellow....(He's not Asian...(NO offense!!)..Long story short , they removed his gall bladder & it looks like he'll be OK...
jsf2323:....I could not find most of the parts you listed......CR4805 does not exist (more in a sec)...U4801 is not the same as yours...You said:..""". Also note some of these parts may not be on your set as these RCA and GE chassis vary so much"""....100% True...
READ ON===>>
I've JUST made a startling discovery...
On the back plate of the "light box" there is attached a very small "service information packet"..In that packet there is a VERY small parts list , parts layout drawings , etc...
The drawing & parts list for the small little "Pincushion board" in that packet do NOT match what is actually in my set...
So , somewhere during the life of that TV , someone subsituted the "169" board for a similiar board...
On the installed board , there is a clearly printed label that says:..TC-169PG..<==.Exactly...
This is the problem I have... IF I order the service manual for P46731AT (which MOST likely has ONLY the 1 IC) , I will NOT get the circuitry I need for the replaced board (which has 2 IC's)...I STRONGLY suspect that the schematic I need is for a "CTC-169PG" which MAY have the circuitry for TDA8146 (14 pins) & 741CN (8 pins) IC's....
So there in a nutshell is my dilema...
I would APPRECIATE help from ANYONE who has a diagram or service manual for a "CTC169PG" board...or knows the cause...
Sorry to hear about your friend hope he is doing OK now. Hey i'm alittle confused because in an earlier post you said you had checked Q4802 with a max voltage of 18v and that U4801 is OK . That led me to give you the voltages for the parts that were listed on the schematic with those parts listed on it . I do have the schematic for the parts you listed , but the schematic is paper form only . RCA did not have CD-rom disc's for those models due to there age . Now you might be able to purchase them if there available @ www.ued.net if they don't have them they are not available. I can give you the voltages to those IC's . U4850 pin (1) no connection (n/c) (2) 1.14v (3) 1.43v (4) n/c (5) 8.71v (6) ground (7) n/c (8) 24.9 (9) 0v (10) 0v (11) 0v (12) 9.95 (13) & (14) n/c Now U4851 pin (1) n/c (2) 12.8 (3) 12.7 (4) ground (5) n/c (6) 12.8 (7) 25.1 (8) n/c . Those a for TDA8146 & 741CN . Q4850 (E) 13.1v (B) 12.7 (C) ground Q4851 (E) 12.7 (B) 12.8 (C) ground . Also check C4801 it is a 47mfd @ 35v that is not on that board but it is on the main board . Follow E1 on your pinchusion board to L4803 which has four legs , the capacitor in off of pin 5 of the coil . E1 has 13.1v which also feeds your Q4850 (E) . This coil (L4803) could also be opened or not working properly. The service manuel i have is paper form and about 15 years old and folds like a map . Hard to copy , but if you get in a pinch let me know i'll see what i can do to mail you something . Or if you need more voltage drops let know as well . Sorry about giving you the wrong voltage drops on the previous post sometimes those chassis vary just enough . James
jsf2323....Good to see ya again...My friend / landlord should be OK soon...
....Thanks...
In reply:==>..
""Hey i'm alittle confused because in an earlier post you said you had checked Q4802 with a max voltage of 18v and that U4801 is OK ""
Q4802 & U4801 is & was OK...The reason is because when I vary R4805 (Pin Amp adjust) , the voltage at the base & collector of Q4802 responded accordingly....
""I do have the schematic for the parts you listed ...
.."..THANK you Jesus!!! & jsf2323
""RCA did not have CD-rom disc's for those models due to there age . Now you might be able to purchase them if there available @ www.ued.net if they don't have them they are not available.""
I went to the Thomson webpage & they have the set listed....However that does NOT mean that I will get the schematic for MY board...I also went to the link in your post for ued.net ...Sorry , but no luck there either...
""The service manuel i have is paper form and about 15 years old and folds like a map . Hard to copy , but if you get in a pinch let me know i'll see what i can do to mail you something .""
THANK you for the offer...I may need it from you...(the ONLY area I'll need is the Pincushion circuit)..
""Sorry about giving you the wrong voltage drops on the previous post sometimes those chassis vary just enough . ""
No need to apologize...Not your fault...I did NOT discover that the "169" was subbed until just recently...(RE:My previous post)
As of now I can tell you some of my volts are off...On U4850, all pin voltages are OK , EXCEPT PIN 9 , which is at 1.1 volt dc...Way off value...Could be due to a pulse loss or bad IC...On U4851 , pins 2 , 3 & 6 are off...All reading at 19 volts dc....I'm betting that that is because I have the width set somewhat high...I will try (tommorrow) to see if a re-adjustment of the width control brings that voltage down or varies...
I will also check out the rest of the info you gave me....
jsf2323: MANY , MANY THANK you's for all the info & your help...
...
I'LL let you know how it goes soon...Ron.M
1.1jsf2323:
1st in reply...
As stated in my previous post , all voltages on U4850 are OK , except pin #12...
The volts on U4851 will vary using the "Width" control & can be set to the volts in your info...
C4801 is a 4.7 mfd @ 35v NP cap in my unit ...ESR & value are OK....
L4803 is not open...
Now I need to make a correction from my previous post..===>
"""As of now I can tell you some of my volts are off...On U4850, all pin voltages are OK , EXCEPT PIN 9 , which is at 1.1 volt dc...Way off value..."""<==That should read PIN # 12 & not #9....My bad...
That said....I'm begining to think that U4850 is bad...I'm concerned about the volts on Pin #12....According to your info , that should be 9.95v...I'm only reading 1.1v dc...The question is: Where does that 9.9v come from ?? Is it coming from the IC internally or a supply source...
jsf2323: Your continued help IS GREATLY appreciated....
...Talk to ya soon....
Check R4856 it is (20K ohm) it supplies 18v and goes to pin 12 . R4863 (18k ohm)is also on the line that goes to ground to pull the voltage to 9.95v . Also on that line is C4853 that supplies the pin adjustment . But that is OK if you have the voltage on U4851 pin 2 @ 12.8v . Sounds like your getting closer . James
jsf2323: Good news, Both R4856 & R4863 check OK...Methinks the IC IS bad....When I desolder Pin 12 , the voltage returns to 9.9 v dc...
......The IC appears to be loading down that voltage....When I get a replacement & install it , I will let you know the results....
BTW, How are you doing on the other set ???
Later , kind sir....
jsf2323: GREAT NEWS !!! ......
..... 
....I found an exact replacement IC , installed it & IT WORKS !!!!....
.. 
.....
All 3 controls are functioning correctly , especially the Pin Amp control....
My main TV is NOW OK...
jsf2323;
.....I wish you nothing but the BEST...
I can't begin to THANK you enough for ALL your help...Without your help , I don't think I could have done it...
THANK you VERY , VERY much....Til we meet again....Ron.M
Way to go man . Its just like riding a bike , you never forget how to repair a TV . The diagram makes a difference . On my problem TV can't find a replacement board and most places say to have it rebuilt is 50/50 as parts are no longer available . PTS & TSM want to charge $60.00 just to look at it even though i've told them which IC is bad they won't comfirm if that part is available . It is one of those IC's that is a surface mount which i hate to replace . They just want my $60 bucks . I've been told this was not a popular model . Just my luck when someone gives me a good TV . Good luck with your TV , Talk to you later , James
jsf2323: Give me some more info about your problem TV & maybe I can help.....ie: Model# , Chassis# , especially the generic IC#....I also HATE those surface mount IC's ...Especialy those 64 or 100 pin types...Later....