Thank very much for all of reply.
I only make use of Isoloader 0.7 beta1 in dreamshell,So there is no AV convertor like SCART or VGAbox.
Now, I think that flickering screen is negligible matter as There is no way to display 50Hz screen correctly in this CRT TV.
And I found that one of GND solder pad In the CPT board have been torn out.
So, I scraped remained solder pad with needle to expose copper surface and soldered it to GND pin.
And this time,I deliberately hindered anode cable from being very close to yoke like below picture.
...
chth96
Senior Member
Last Activity: 07-18-2024, 09:10 PM
Joined: 11-07-2022
Location: jakarta
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Last edited by chth96; 07-10-2024, 09:55 AM. -
Thank very much for all of reply.
It seems that the program(Isoloader 0.7 beta1 in dreamshell) don't enable real 50Hz mode.
By the way,I found that there is small crack on the one of GND soldering joint in the CPT board ,So I soldered it and all of other large pins on the CPT board like below picture.
[URL]https://www.dropbox.com/scl/fi/zp4zw3q80syfop3r11383/20240709_112203.jpg?rlkey=ttl604db2m7imk2s1cmngy1c7&st=wc083ly5&dl=0[/URL]
When I switched on TV,I confirmed that It display screen like yesterday,But Now I heard quite loud noise from anode...Leave a comment:
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Thank very much for all of reply.
It is not possible to purchase bi-polar capacitor which has 5.6µf/50v specification,So I still not yet replaced it.
I noticed that There was a crack in some pins of Q408(KTD2059-Y) and IC601(it look like below screenshot).
[URL=filedata/fetch?id=3304881&d=1720429947][ATTACH=JSON]{"alt":"Click image for larger version Name:\tIMG_20240707_114609.jpg Views:\t0 Size:\t6.51 MB ID:\t3304881","data-align":"none","data-attachmentid":"3304881","data-size":"medium"}[/ATTACH][/URL]...Last edited by chth96; 07-08-2024, 05:40 AM.Leave a comment:
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When I desoldered R831 and solder 60w bulb, I measured B+ filter capacitor and It was measured 120Vdc.
So I think that there is no faulty in the HOT area. So I doubted maybe there was loose contact on the pin of IC,Beacuse This CRT TV was manufactured over 25 years,So solder joint would not as tight as twenty five years ago.
And it seems that weight of its PCB is about 2kg,I think that Whenever I deposited this heavy PCB on the floor,this would put pressure on the pin of [URL="http://ic.so/"]I[/URL]C ,So there would be minor crack on its solder joint.
...Last edited by chth96; 07-05-2024, 11:44 PM.Leave a comment:
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I replaced ZD808 zener diode with 1N4737,But it won't repair black screen symptom,and there is no difference between these zener diode in measuring cathode voltage(7.1Vdc)
I think that I need to connect a 40w 60w bulb to B+ soldering point of Flyback transformer,But I don't know the process to substitute for the Flyback's B+ Load with a blub in detail.Leave a comment:
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Thank you very much for reply.
I just have measured DC voltage of C812 by placing red probe to positive terminal of C812 and placing black probe to negative terminal of C808 in HOT area(400V 470uf the biggest capacitor in the circuit).
It was measured 10.8DCV.
And I measured cathode of ZD808,It was measured 7.1DCV and Q800(C3852A) base was also measured 7.1 DCV.
Q800(C3852A) collector was measured 10.8DCV.and pin#9 of STR-S6707 was measured 6.4DCV.
I desoldered C812 and I check it with LCR T4 meter. Its capacitance was still within 10% tolerance(23uf)...Leave a comment:
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The strange thing is whenever I measure the DC voltage of pin#9 of STR-S6707, It is measured 6.4V.
As far as I know,It should be measured at least 7.6V in order to go On-State Voltage.
I doubted any diode near STR-S6707,So I checked it using analogue meter(x10 ohm) But It showed only one reading with the correct and opposite polarity of probe.Leave a comment:
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Thank very much for reply.
there is no inductor left or right to the transformer.
I saw H46 or H90 schematic which you have attached, But it seems that it is totally different to the circuits which I tried to repair.
And I saw MC-7CA schematic and at least It is somewhat similar to STR-S6707 area in the circuits.
You can compare STR-S6707 area in the MC-7CA schematic to my drawing of circuits which contains resistor and capacitor near STR-S6707.
[ATTACH=JSON]{"alt":"Click image for larger version Name:\tscan0001.jpg Views:\t0 Size:\t2.68 MB...Leave a comment:
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Thank you very much for reply.
I roughly draw most of flyback transformer's soldering point and its nearby components on the circuits.
I noticed that B+ soldering point is coupled to three carbon resistor(R432,R437,R831) and C829 is the big capacitor.
Should I isolate B+ soldering point by desoldering these three carbon resistor(R432,R437,R831) from circuits In order to connect 240v lamp and test it?
And where should I solder 240v lamp on the bottom of PCB?
[URL=filedata/fetch?id=3296825&d=1719329218][ATTACH=JSON]{"alt":"Click image for larger version...Leave a comment:
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I finally soldered LITEON LTV817 D grade on the PCB circuit of 29inch CRT TV and switched on this CRT TV.
It still displayed black screen. And It seems that it doesn't glow inside of the tube neck at all...
and Moreover, After switching on I measured voltage of this big capacitor(160v 100uf) on the cold side,which seems to be B+ filter capacitor,It was measured only 37-38 voltage in DC Voltage mode of analogue meter,But before I replaced opto-coupler with LITEON LTV817 D grade,It was measued nearly 45 DC voltage.....Leave a comment:
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I purchased LITEON LTV817 D grade. But PC817 Optocoupler, which was defective, was C grade and made in Sharp corperation.
Is it Okay to replace C grade PC817 from Sharp corperation with D grade LITEON LTV817?...Leave a comment:
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I have desoldered PC817 Optocoupler from PCB of this CRT TV and tested it by following below youtube tutorial.
[URL]https://www.youtube.com/watch?v=SPSwvVpMrvc[/URL]
I confirmed that a led light turned on, But unfortunately, When I measure its resistance of pin 3 and pin 4 with10k ohm range of analogue meter, I saw that It display two reading of low resistance when checking both way.
I think that following youtube tutorial spoiled PC817 Optocoupler, So I need to find any local store where sells it.https://I have desoldered PC817 Opto...t by following...Leave a comment:
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partnumber on the surface of main PCB and small PCB is
MC-7CA(MAIN) 6870VM0056C(6) 980424 L.W.G(0)
MC-7CA(CPT) 6870VS0167A(1) 971014 K.J.B(0)
and model number of This LG CRT TV is CN-29H3
Frankly speaking,I posted a thread about this CRT TV in the reddit forum.But It seems that there is no way to find the culprit of no display symptoms.
[URL]https://www.reddit.com/r/ElectronicsRepair/comments/1cb7m6y/how_can_i_check_str_6707_regulator[/URL]https://partnumber on the surface of...056C(6) 980424...Leave a comment:
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Is it means that this [B]non-polarized capacitor[/B](samwha NF capacitor 50v 5.6uf) has nothing to do with symptoms of no display after I heard sound of inrush of current to TV?Is it means that this [B]non-polarized capacitor[/B](samwha NF capacitor 50v 5.6uf) has nothing to do with symptoms of no display after I heard sound of inrush of current to TV?Is it means that this [B]non-polarized capacitor[/B](samwha NF capacitor 50v 5.6uf) has nothing to do with symptoms of no display after I heard sound of inrush of current to TV?...Leave a comment:
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How can I test non-polarized capacitor?
I desoldered samwha NF capacitor(50v 5.6uf) from PCB circuit of 29inch CRT TV which have symptoms of no display after I heard sound of inrush of current to TV whenever I switch on this television.
I measured ESR value of this non-polarized capacitor(samwha NF capacitor 50v 5.6uf) by means of MESR-100 ESR meter and It displayed 0.3 ohm
And When I measured its capacitance with digital multimeter and LCR-T4 Mega328 meter, It displayed 10uf from DMM and 8uf from LCR-T4 meter.
I found catalogue of samwha capacitor(samwha-catalogue_3.pdf file), which is attached to this thread,... -
Does WCAP-ATG5 has similar or better quality than smahwa capacitor?
I want to replace samhwa RG 250v 1uf capacitor which has no ESR value and has capacitance less than 280pf.
It is possible to purchase WCAP-ATG5 in local electronic shop.
But I want to know that whether WCAP-ATG5 capacitor has similar or better quality than smahwa capacitor or not.
Is there anyone who has experience to replace any bulge or faulty cap with cap from Wurth Elektronik?
[url]https://www.we-online.com/en/components/products/WCAP-ATG5[/url]https://I want to replace samhwa RG ...It is possible -
Thank you very much for reply!
By the way, I found that there is a bad capacitor(samhwa RG 250v 1uf) which doesn't have any ESR ,when I measured it with MESR-100 and its capacitance is less than 250 nf.
this bad capacitor is very close V-DY and H-DY connector.
And another capacitor(smahwa SG 250v 4.7uf) is directly connect to 160V soldering point which is connected to cpt board.
and its ESR value is higher than 10 ohm.
Is it possible to replace smahwa SG 250v 4.7uf with lelon rga 400v 4.7uf and replace samhwa RG 250v 1uf with any capacitor of 105 degree 250v 1uf ...Leave a comment:
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Thank you very much for your reply! I also measured all of caps on the small PCB which should be connected to cathode ray tube. By the way, I saw below youtube video. Although I can not understand the language youtube uploader speaks,But it seems that He demonstrate How to check Str 6707 with DMM's diode mode. [url]https://www.youtube.com/watch?v=jl0POb5TeDY[/url] So I desoldered Str 6707 from HOT area in PCB and followed the way he demonstrated like below dropbox link. [url]https://www.dropbox.com/scl/fi/b4t7geljhon1w45yel7wz/20240423_230828.mp4?rlkey=vfujf0qzfa3e0l830okewegir&st=iblh3aea&dl=0[/url]...Leave a comment:
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I replaced all of bad caps and I also replaced another SMS capacitor 160v 2.2uf from Korea chemicon with Rubycon YX which is very close to D1879 transistor.
[URL="https://www.badcaps.net/forum/general-topics/general-capacitor-questions-issues/3255734-is-it-no-harm-to-replace-with-capacitor-without-ripple-current-rating"]Is it no harm to replace with capacitor without ripple current rating? - Badcaps[/URL]
I assembled CRT TV's PCB and plug into all of appropriate connector.
When I connect AC power cord to power outlet without switch on CRT TV, I noticed there is no a...Leave a comment:
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I always replace bad capacitor with "a capacitor which has higher or same difference ripple current rating",If it is located in SMPS PCB.
But Is it OKAY to replace with "a capacitor with a lot lower ripple current rating", which is adjacent to D1879 transistor in COLD area of PCB?Leave a comment:
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