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Is it impossible replace bi-polar capacitor with film capacitor?
Posted by bshi02 on 16 Jul, 2024 16:04 -
I repaired 29 inch CRT TV,BUT...I noticed that There is always overlapping white gradient letter like below link.
https://www.dropbox.com/scl/fi/oxtwbrt824k8s7hz4rf55/20240716_224510.jpg?rlkey=zslga97y32kba1yhi73xubhd6&st=2em23akf&dl=0
I found that a bi-polar capacitor(C433 SAMWHA NF series 5.6uf 50v), which is next to Q408 KTD2059-Y transistor and close to AN5521 IC in the attached schematic(lg_chassis_mc-7ca_sch pdf file),actually has large capacitance(10uf).
https://2.imimg.com/data2/SD/JD/MY-/samwha-catalogue.pdf
I think that this problem(overlapping white gradient letter) has something to do with out of capacitance tolerence of this bi-polar capacitor.So I want to replace this NF series capacitor.
But it is impossible to find bi-polar capacitor which has 5.6uf specification.
Luckily,I found that I can purchase ECW-F2565JA from where I live.
https://www.eleparts.co.kr/goods/view?no=10864147
By the way,Is it impossible replace bi-polar capacitor with film capacitor?
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Normally, a bi-polar electrolytic can be replaced by a film capacitor (PE or PP).
The original part was probably chosen since it had a lower price and possibly smaller size than an appropriate film capacitor. -
Both! The film cap is larger and more expensive. An alternative would be to use a 2.2 µF and a 3.3 µF bi-polar cap in parallel.
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I do not see the gradient, but it seems that the capacitor is in the horizontal deflection circuit, not in the video path. Here normally you could expect some distortion or fails in high voltage.
Normally to substitute a bipolar electrolytic with other type, the problem is the size. The advantage of electrolytics is the size. -
Thank very much for all of reply.
If you enlarge below image There is overlapping gradient on the background(PRODUCED BY OR UNDER LICENSE FROM SEGA ENTERPRISES) it is somwhat like JPEG Compression Artifacts.
https://www.dropbox.com/scl/fi/oxtwbrt824k8s7hz4rf55/20240716_224510.jpg?rlkey=zslga97y32kba1yhi73xubhd6&st=2em23akf&dl=0
By the way, I looked through samwha-catalogue and I found that NF series was exclusively Designed for horizontal deflection current correction in TV,high frequency anf high ripple current(135 page)
https://2.imimg.com/data2/SD/JD/MY-/samwha-catalogue.pdf
Is it really Okay to replace bi-polar capacitor ,which was exclusively Designed for horizontal deflection current correction, with general film capacitor? -
A replacement with a foil capacitor usually works, if there is enough space. I would look for MKS type as that is often the smallest size and the electrolytic capacitor anyway has poor DA and series resistor. So no need for a low loss cap like PP. For this special type one may have to look for sufficient riplle current rating, which may exclude the smallest form factor.
I agree with JZX: a bad part in the defelction circuit would cause a geometry problem / image distortion, but not an intensity problem.
The shaddow following a sharp contrast is more a thing of signal reflection. A classical case was a problem (impedance mismatch and thus reflection) in the antenna cable. If this is with a PAL signal, it could in theory be the delay line, though this should be more a color issue than.
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Thank you very much for detailed reply which contains useful information.
A replacement with a foil capacitor usually works, if there is enough space. I would look for MKS type as that is often the smallest size and the electrolytic capacitor anyway has poor DA and series resistor. So no need for a low loss cap like PP. For this special type one may have to look for sufficient riplle current rating, which may exclude the smallest form factor.
I agree with JZX: a bad part in the defelction circuit would cause a geometry problem / image distortion, but not an intensity problem.
The shaddow following a sharp contrast is more a thing of signal reflection. A classical case was a problem (impedance mismatch and thus reflection) in the antenna cable. If this is with a PAL signal, it could in theory be the delay line, though this should be more a color issue than.
I search for MKS type capacitor which has specification of 5.6uf and over 50V,But It seems that ,Except for ECW-F2565JA and below link MKT capacitor(HMF-27.5 B/K( 5.6uF / 250V)), It is impossible to purchase Any bi-polar capacitor from where I live which meet the condition of 5.6uf and over 50V.
https://www.icbanq.com/P000511234
I repaired 29 inch CRT TV,BUT In fact,If I unplug its AC cable and A few hours later I switch it on , It display blurry image for 3-7 minutes. So I doubted that ,as well as problem of the shadow following a sharp contrast, it would also be caused by incorrect 50v 5.6uf bi-polar capacitor which is located in the defelction circuit..
Although I use composite cable and This is 60Hz NTSC TV,But there was no shadow following a sharp contrast When I connected this composite cable to different CRT TV.
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If it is blur in all directions, is a problem of the focusing circuit (high voltage).
If it is only blur in horizontal direction (ie, horizontal stripes are well defined but not vertical lines), is a problem of the path of video, loss of bandwidth.
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If it is blur in all directions, is a problem of the focusing circuit (high voltage).
Thank you very much for reply.
If it is only blur in horizontal direction (ie, horizontal stripes are well defined but not vertical lines), is a problem of the path of video, loss of bandwidth.
Blur screen usually appears when I plug ac cable and as soon as switch it on, and This Blur screen usually only last 3-7 minutes, After that It displays normal not blur screen at all.
I confirmed that It only blur in horizontal direction(it has even more terrible shadow following a sharp contrast than a picture which I uploaded to dropbox yesterday)
It seems that there is cold soldering in the path of RGB connection.
Then Should I resolder any components which is close to RGB pin of TB1231N and any components which lies in the trace of RGB connector in CPT board? -
As all colors suffer the same fail, if it is a broken solder must be a common one, perhaps gnd, or the mesh of cable.
You can carefully fiddle with an isolating stick to find the fail (a plastic ruler for example), using a mirror to see the screen. -
What I do see is a reflection on the video signals. For instance, there is a repetition of the vertical bar in the "E" letters that is about midway to the right in the same character. This is either due to improper termination resistors or crummy cable that does not have the right characteristic impedance. Crummy VGA cables just have a bundle of wires in a shielded jacket, while good ones have individual coax cables for at least the R G B signals, and maybe the sync signals too. In desperation, I have made my own cables with 5 runs of RG-178 mini-coax.
Blur screen usually appears when I plug ac cable and as soon as switch it on, and This Blur screen usually only last 3-7 minutes, After that It displays normal not blur screen at all.
I confirmed that It only blur in horizontal direction(it has even more terrible shadow following a sharp contrast than a picture which I uploaded to dropbox yesterday)
It seems that there is cold soldering in the path of RGB connection.
Then Should I resolder any components which is close to RGB pin of TB1231N and any components which lies in the trace of RGB connector in CPT board?
Jon -
One can use the delay from the gost image to get an estimate for the length of the cable / trace that has bad termination. For the picture is looks like already quite some fraction of a horizontal line and nor just a few inches on the PCB.
Usually it needs bad termination on both sides or 2 spots to really get a reflected signal. There may not actually be a defect, but it could be just 2 bad designs coming together. It may be worth testing with a longer / additional cable at the input and see if this shifts the artifacts further away. -
What type of signal are you using ? (RGB, composite ...)
Have you another input? -
I repaired 29 inch CRT TV,BUT...I noticed that There is always overlapping white gradient letter like below link.
https://www.dropbox.com/scl/fi/oxtwbrt824k8s7hz4rf55/20240716_224510.jpg?rlkey=zslga97y32kba1yhi73xubhd6&st=2em23akf&dl=0
I found that a bi-polar capacitor(C433 SAMWHA NF series 5.6uf 50v), which is next to Q408 KTD2059-Y transistor and close to AN5521 IC in the attached schematic(lg_chassis_mc-7ca_sch pdf file),actually has large capacitance(10uf).
https://2.imimg.com/data2/SD/JD/MY-/samwha-catalogue.pdf
I think that this problem(overlapping white gradient letter) has something to do with out of capacitance tolerence of this bi-polar capacitor.So I want to replace this NF series capacitor.
But it is impossible to find bi-polar capacitor which has 5.6uf specification.
Luckily,I found that I can purchase ECW-F2565JA from where I live.
https://www.eleparts.co.kr/goods/view?no=10864147
By the way,Is it impossible replace bi-polar capacitor with film capacitor?
Hi,
Why don't you test the old cap?
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Thank very much for all reply.
I use composite cable because It(29 inch CRT TV) has only composite video input connector. and I have two composite cable which are similar in length(2 meter).
and Neither of two composite cable won't fix the problem of shadow following a sharp contrast.
I resoldered all pin of TB1231N and LG8708-08A,GL3812 and most of components which is adjacent to these IC and some pins of transistor.
although ,As soon as I switch on TV, There still exist blur in horizontal direction, But Now It seems that It only last about 3 minutes.
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As It seems that old bi-polar cap(C433 SAMWHA NF series 5.6uf 50v) only affect on vertical direction,and It seems that there is no defect in vertical direction, So I take advice to not replace old bi-polar cap with film capacitor
Why don't you test the old cap? -
Are you talking about color fringing around the fine print? Please circle the problem, you may be chasing nothing. Minor visual artifacts using a consumer TV as a video game monitor is to be expected. Consumer TVs are full of design compromises that give a less than perfect picture that looked right enough watching TV sitting a typical distance from it, I would consider 3 minutes is acceptable 100% warm up time, especially if the tube has a lot of hours on it.
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As It seems that old bi-polar cap(C433 SAMWHA NF series 5.6uf 50v) only affect on vertical direction,and It seems that there is no defect in vertical direction, So I take advice to not replace old bi-polar cap with film capacitor
Not, it is not that. If you have a problem of bad signal, low bandwith, bad edges (as seen on oscilloscope) you will have only blurriness in horizontal, because they are short time defects, fast, and up or down in screen there are different lines, with big (64us each) time difference.
If you have a defect in tube focusing (adjusted by a relatively high tension applied to an electrode of the tube), basically the cathodic ray is too fat, and all is blurry.
This capacitor is in the horizontal deflection circuit, and deflection fails show as distortions of picture, somethig like this as example https://www.aussiearcade.com/uploads/monthly_2022_06/1655766189207925289881820095742.thumb.jpg.0ecbc2624af88820f424b2280dc9710e.jpg, big area distortions, not details. The cathodic ray do not scan correctly the screen.
Fails in H deflection also can affect to the generation of high tensions. And often, massive destruction of horizontal output transistor and flyback transformer. So is better not to do experiments in this section.
At first i though the problem was another, if the problem are the edges of letters, i would not call this "gradient", but it can be a language problem (my english is crap
).
If this is the problem, the cable can be the cause. Try with a 75 ohm cable (tv aerial cable), try with another video source also. -
I replaced C406 capacitor(samyoung SMS 160v 2.2uf) with same spec of rubycon YK(160v 2.2uf) which is connected to Horizontal Driver Transformer ,But It did not solve the problem of "shadow following a sharp contrast",rather I heard loud static noise from anode cap.
I was disappointed,So I desoldered rubycon YK(160v 2.2uf) and resoldered its natural capacitor(samyoung SMS 160v 2.2uf),Then I plugged its AC cable and switched it on, It displayed same screen as before,, BUT TO MY SURPRISE,
It sounds very weird loud noise from anode cap and CPT board!!!
I recorded this weird noise with my android phone like below dropbox link.
https://www.dropbox.com/scl/fi/7p4rplxq97bgu81ed6u65/20240719_193719.mp4?rlkey=6uuhdi5269t1g54sejtnbk6gn&st=t5jj2bgl&dl=0
https://www.dropbox.com/scl/fi/2bkva1qg3euxwzy1prbhe/20240719_193926.mp4?rlkey=5okqp19cvy13t6idve1olzmyl&st=lub4p6bv&dl=0
Although anode cap have been slightly torn in the center,But I have used this anode cap and I never have ever
experience in hearding this kind of weird noise from CRT TV at all.
https://www.dropbox.com/scl/fi/qn6cpen3rk736p1yi5q0z/20240719_101445.jpg?rlkey=vptenek5i9xw2o5dckzhsmgxa&st=uw78ur2f&dl=0
I also measured capacitance of natural capacitor(samyoung SMS 160v 2.2uf) it was 2150nf and its ESR value was 5.3ohm.I think that this natural capacitor is not defective..
it is at present impossible for me to found the reason why It start to sound weird noise from anode cap since I repeat desoldering and soldering C406 capacitor...
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Why have you changed that capacitor? It is in the H deflection circuit, the video signal does not pass through this part of circuit.
Dont mess with the horizontal deflection if is working well, it works with high voltages and high currents, (normally not at same instant but ..,) and any error or failure can end in destruction of FBT and/or final (mostly "and") transistor, and other components.
What is cpt board?
I do not identify the sound in the recording. Sound like sparks? Is the picture stable when you ear the sound?
Are you sure that the sound is generated under the anode cap?
Perhaps you have moved the anode cap pulling the HV wire?
Before you touch the anode cap, remember that the anode contact in the side of crt is connected to a internal capacitor (the glass of tube) that may be charged at 28000-30000 V. Sometimes is not letal
but I would not touch, just in case.
You should discharge the tube and then you could clean the inner part of the cap ant the glass around the anode contact. But not without discharging the tube.
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I'm sorry that I misunderstand that somewhat higher ESR means depleted capacitor.So I replaced natural capacitor(samyoung SMS 160v 2.2uf) with new capacitor..But It seems that rubycon YK(160v 2.2uf) has alot lower ripple current value than the same spec of SMS capacitor..
If you browse through attached pdf file(lg_chassis_mc-7ca_sch),You will find CPT board at the left-hand edge.(It is CRT neck board)
I just have recorded another video which seems sound alot louder than pervious recording video.
Although It display normal screen as before,,But I really dread of breaking out fire or explosion at some future day, If I continute to use this CRT TV..
https://www.dropbox.com/scl/fi/w5w818wq9ort5lhflj73y/20240719_214918.mp4?rlkey=oisa2irppfyozn429pgh4kgwh&st=otprket8&dl=0
I discharged the tube and cleaned the inner part of the cap and the glass around the anode contact But It seems that it won't get rid of weird sound...
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I see the cpt board.
Don't use the tv until repaired. If the sound are sparks can make a fire.
C406 seems to be a decoupling capacitor for the horizontal driver, and R416 is relatively high. Perhaps is to limit the current if T401 or to lower the voltage (not very good method)
You need to locate the origin of sparks. It is difficult to identify the noises in the recording.
Check if the high voltage wire is well inserted in the fbt. In some fbts this cable is replaceable, and if it is loose, you can have sparks in the "connector" (is a hole where you put the wire with the end peeled, and a collar to retain it.). Send a photo of the point of entry of the cable in the fbt.
Check if the ground wire is well connected to the braid that is in contact with the exterior of thr crt. (the G point in cpt board)
You can power the tv in a dark room (have a flashligh in hand
), wait a time to adapt the sight to darkness an look for sparks.
You can also use a plastic pipe over your ear as stethoscope to search the origin of noises. Use a moderately long pipe, at least 30 cm, you don't want your ear too near from high voltage.
And don't mess more with the horizontal deflection, your original trouble is not here almost surely.
These are old tricks, be careful and do not work alone, is better to have somebody that can disconnect power in case of accident, crt tvs are dangerous.
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Thank you very much for always giving me response!
below picture is all of cable which goes from FBT
https://www.dropbox.com/scl/fi/e3hoeaz9psa9dlel8neof/20240720_093115.jpg?rlkey=vhec0tgbvxtuwtz8xaqoa07qo&st=nzx3jnfm&dl=0
https://www.dropbox.com/scl/fi/0wh7t1y0qvhnyj0zqzs9a/20240720_093139.jpg?rlkey=ryrr267y6udrecgc8nqz5njg6&st=ev5nr8ow&dl=0
https://www.dropbox.com/scl/fi/va6q5nqwgxrjahxb5dh5u/20240720_093158.jpg?rlkey=da69b6ncy62nbpce9eeyedadm&st=bg0jxgra&dl=0
https://www.dropbox.com/scl/fi/6c6un9bmcnjspwkpky454/20240720_093216.jpg?rlkey=x86a8vc3a4oo4jo4k8ptudmid&st=9cd8xyyc&dl=0
https://www.dropbox.com/scl/fi/3m4ftk2pkfb51s3pbd68u/20240720_093222.jpg?rlkey=0y549rl508c3tmysghigja5r2&st=8dzko8km&dl=0
https://www.dropbox.com/scl/fi/9ao5ep26o2u27ym0615ie/20240720_093103.jpg?rlkey=hevgb671v6e1150c6fj411uc0&st=pb94bt5v&dl=0
As I don't any plastic pipe So I make use of paper biscuit box like below picture in order to hearing noise.
https://www.dropbox.com/scl/fi/03oh2jb8jaj865ssufryq/20240720_150905.jpg?rlkey=jihdz50oh116gk49i2hejya46&st=l63xb2bf&dl=0
It seems that the origin of noises is FBT.It obviously sound very weird.
and There is also static sound and phut sound from anode cap...
It seems that When I replaced C406 capacitor with low grade rubycon YK capacitor,It caused failure of FBT...
As there is no FBT which is compatible with LG 154-179M FBT and It seems that it is impossible to purchase LG 154-179M FBT from where I live,In the last resort, I will purchase SHL 160v 2.2uf Capacitor and replace with it. -
-Check all solders of fbt with a magnifier glass. Perhaps one is cracked when you have moved te main board.
-Try to push the anode wire into the fbt (if it is removable, it can go out a bit.
-Check to see if some component han bee bent when you have moved the board.
-Check around C406 an the other capacitor to see if there is tin splats, o something abnormal.
You can destroy the fbt changing random components in the deflection circuit, you know, but if there is a picture, and is normal, probablily is not destroyed yet.
Why have you changed C406?