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Author Topic: Chinese Chassis , need help.  (Read 599 times)

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abispac

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Chinese Chassis , need help.
« on: March 20, 2020, 12:17:42 pm »
So yesterday i bought a monitor 19 inch, for next to nothing, it had one chassis, but since it had a clearly blown cap, i ask the guy if i could take another chassis he had laying around so maybe out of the 2 i can make a working one. Anyway bot chassis are very similar, i tested both and i hear noise, but not as the loud noise all monitors make when they turn on, also there was no static on the screen, and the screen looks black, no white noise image. I know i do have to make a cap change, especially the big one, but im just asking for advice, anything else i can look for? both chassis build a charge, as when i discharged the monitor i could hear the big spark comming out. , thanks for any advice.

lilshawn

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Re: Chinese Chassis , need help.
« Reply #1 on: March 20, 2020, 01:02:57 pm »
I can count on one hand the number of big main filter caps i've had to change, and i've been doing repairs for 12 years. i'd suspect this marked cap...(see attached)

mainly becasue the sleeve has moved down over the edge of the cap body...meaning it's gotten really hot and shrunk the sleeve.

abispac

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Re: Chinese Chassis , need help.
« Reply #2 on: March 20, 2020, 08:07:57 pm »
Thanks for the advice, i dont have a cap with the same values at the moment, im gonna buy it tomorrow, but wont have a chance to test it till Monday, but, on a closer inspection, that part i highlighted in red was loose and flamed, i did check it for continuity and it came out, good, so for now, im a solder it, and test it to see if it works, if not, im gonna have to buy it to. Also , the other chasis its near identical, but the dont have the same caps, and it does not have that loose part , but definitely the big main cap needs to be replaced as its does look blow, ill post a picture later.

abispac

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Re: Chinese Chassis , need help.
« Reply #3 on: March 20, 2020, 08:38:48 pm »
so after soldering that part on chasis number 1, the monitor turned on with  a unstable image, hope someone can tel me the fix,  in the meantime chasis number 2 i do believe the main cap its blow, just look at the picture and see that extra round at the top, like its inflated. wat do you think?
chasis number one video
https://streamable.com/zc4yq



abispac

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Re: Chinese Chassis , need help.
« Reply #4 on: March 20, 2020, 09:34:14 pm »
chasis number 2 looks totally dead, and cant find avius things, beside the burnt area, and the main extra round giant cap, one thing its curius althought its dead, the monitor builds a little charge, not to loud but a good one.

lilshawn

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Re: Chinese Chassis , need help.
« Reply #5 on: March 21, 2020, 12:08:19 am »
carefully cut the top of the sleeving and remove the top (it's just a round disk of plastic) and see if the metal can itself is domed, or it's just the plastic. I have seen some of those with bubbly looking tops, but it's just the plastic.

the strange part you took photos of is an induction coil. it's just wire wrapped around a ferrite core. it does look like it had a bad solder joint that went hot and burned off. it can happen especially if you have a bad capacitor on the same line. the inductor filters the little bit of ripple out of the power and converts it to magnetism... if the capacitor on the line is dead...all kinds of ripple needs to be filtered...the core cant handle all the magnetism and produces heat. i've seen them get so hot they catch fire.

your video looks like you have a vertical deflection issue it could be something around that 20 pin IC chip. i'd replace the electrolytic capacitors around that IC.  i'd also change out the little yellow one next to the IC it's a "tantalum" capacitor. I just replace it with regular electrolytic...those tantalum caps are notorious for going sketchy. that cap should have a couple numbers printed on it like

22
25

this means 22uF and 25 volts.

likewise

4.7
35

means 4.7uF 35 volts.

I just replace it with the same uF value and the same voltage or higher (50 volts is fine)

abispac

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Re: Chinese Chassis , need help.
« Reply #6 on: March 21, 2020, 09:25:35 am »
carefully cut the top of the sleeving and remove the top (it's just a round disk of plastic) and see if the metal can itself is domed, or it's just the plastic. I have seen some of those with bubbly looking tops, but it's just the plastic.

the strange part you took photos of is an induction coil. it's just wire wrapped around a ferrite core. it does look like it had a bad solder joint that went hot and burned off. it can happen especially if you have a bad capacitor on the same line. the inductor filters the little bit of ripple out of the power and converts it to magnetism... if the capacitor on the line is dead...all kinds of ripple needs to be filtered...the core cant handle all the magnetism and produces heat. i've seen them get so hot they catch fire.

your video looks like you have a vertical deflection issue it could be something around that 20 pin IC chip. i'd replace the electrolytic capacitors around that IC.  i'd also change out the little yellow one next to the IC it's a "tantalum" capacitor. I just replace it with regular electrolytic...those tantalum caps are notorious for going sketchy. that cap should have a couple numbers printed on it like

22
25

this means 22uF and 25 volts.

likewise

4.7
35

means 4.7uF 35 volts.

I just replace it with the same uF value and the same voltage or higher (50 volts is fine)
thanks ill post results.

abispac

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Re: Chinese Chassis , need help.
« Reply #7 on: March 21, 2020, 11:00:05 pm »
do you have an advice on what to look at chasis number 2 which is dead, beside the bubble big capacitor? the coil things were from chassis number one which it turned on. Thanks for the help.

lilshawn

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Re: Chinese Chassis , need help.
« Reply #8 on: March 22, 2020, 12:53:38 am »
do you have an advice on what to look at chasis number 2 which is dead, beside the bubble big capacitor? the coil things were from chassis number one which it turned on. Thanks for the help.

check the 2 glass fuses near where the power goes in. it could be that one or both are no good. they don't look completely fried...but could have broken due to vibration.

if nothing looks obviously wrong, without a schematic for them...it's going to be tough to figure out what the issue is. you could just randomly start replacing things (called "shotgunning")  and hope for the best. knowing nothing, other than it doesn't work... maybe a blown horizontal output transistor. maybe a fault in the main B+... could just be old dried out capacitors... hard to say. it might be impossible to find information.

is there any indication of a part number or model or manufacturer or anything on the outside or back side of the chassis? maybe a sticker or something on the heatsinking around the flyback transformer...I don't see any Identifying marks or numbers in any of the photos you posted so far.

if you can't find anything you'd basically have to resort to reverse engineering how the chassis is SUPPOSED to work...then test it to find out what isn't working. Something that is going to be very difficult to do unless you know what to look for and expect.

abispac

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Re: Chinese Chassis , need help.
« Reply #9 on: March 23, 2020, 09:44:17 pm »
carefully cut the top of the sleeving and remove the top (it's just a round disk of plastic) and see if the metal can itself is domed, or it's just the plastic. I have seen some of those with bubbly looking tops, but it's just the plastic.

the strange part you took photos of is an induction coil. it's just wire wrapped around a ferrite core. it does look like it had a bad solder joint that went hot and burned off. it can happen especially if you have a bad capacitor on the same line. the inductor filters the little bit of ripple out of the power and converts it to magnetism... if the capacitor on the line is dead...all kinds of ripple needs to be filtered...the core cant handle all the magnetism and produces heat. i've seen them get so hot they catch fire.

your video looks like you have a vertical deflection issue it could be something around that 20 pin IC chip. i'd replace the electrolytic capacitors around that IC.  i'd also change out the little yellow one next to the IC it's a "tantalum" capacitor. I just replace it with regular electrolytic...those tantalum caps are notorious for going sketchy. that cap should have a couple numbers printed on it like

22
25

this means 22uF and 25 volts.

likewise

4.7
35

means 4.7uF 35 volts.

I just replace it with the same uF value and the same voltage or higher (50 volts is fine)
you were right, big cap looks good, now, the yellow cap has a marc of c225, what would be the equal to a regular cap? thanks for the help

Ken Layton

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Re: Chinese Chassis , need help.
« Reply #10 on: March 23, 2020, 10:26:02 pm »
Thanks for the advice, i dont have a cap with the same values at the moment, im gonna buy it tomorrow, but wont have a chance to test it till Monday, but, on a closer inspection, that part i highlighted in red was loose and flamed, i did check it for continuity and it came out, good, so for now, im a solder it, and test it to see if it works, if not, im gonna have to buy it to. Also , the other chasis its near identical, but the dont have the same caps, and it does not have that loose part , but definitely the big main cap needs to be replaced as its does look blow, ill post a picture later.

That circled part looks like an inductor NOT a capacitor.

abispac

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Re: Chinese Chassis , need help.
« Reply #11 on: March 23, 2020, 11:18:01 pm »
Thanks for the advice, i dont have a cap with the same values at the moment, im gonna buy it tomorrow, but wont have a chance to test it till Monday, but, on a closer inspection, that part i highlighted in red was loose and flamed, i did check it for continuity and it came out, good, so for now, im a solder it, and test it to see if it works, if not, im gonna have to buy it to. Also , the other chasis its near identical, but the dont have the same caps, and it does not have that loose part , but definitely the big main cap needs to be replaced as its does look blow, ill post a picture later.

That circled part looks like an inductor NOT a capacitor.
yeah i think it is, but it only had broken solder, which after i fix them the chassis worked, but with a flaw image, ima do a full cap restoration, and hope that fixes the image. I just need to know the equivalent to the c225 yellow cap.

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Re: Chinese Chassis , need help.
« Reply #12 on: March 24, 2020, 12:19:54 am »
Thanks for the advice, i dont have a cap with the same values at the moment, im gonna buy it tomorrow, but wont have a chance to test it till Monday, but, on a closer inspection, that part i highlighted in red was loose and flamed, i did check it for continuity and it came out, good, so for now, im a solder it, and test it to see if it works, if not, im gonna have to buy it to. Also , the other chasis its near identical, but the dont have the same caps, and it does not have that loose part , but definitely the big main cap needs to be replaced as its does look blow, ill post a picture later.

That circled part looks like an inductor NOT a capacitor.
yeah i think it is, but it only had broken solder, which after i fix them the chassis worked, but with a flaw image, ima do a full cap restoration, and hope that fixes the image. I just need to know the equivalent to the c225 yellow cap.
You've probably already cleaned it up, but it looks like some solder splatter from the overheated coil may have shorted the 2nd and 3rd traces below L301.

Even if your multimeter shows no short between the traces, microscopic solder globules can create an arcing short-circuit path when power is applied and more current/voltage is passing through the traces.




Scott

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Re: Chinese Chassis , need help.
« Reply #13 on: March 24, 2020, 10:48:20 am »
Thanks for the advice, i dont have a cap with the same values at the moment, im gonna buy it tomorrow, but wont have a chance to test it till Monday, but, on a closer inspection, that part i highlighted in red was loose and flamed, i did check it for continuity and it came out, good, so for now, im a solder it, and test it to see if it works, if not, im gonna have to buy it to. Also , the other chasis its near identical, but the dont have the same caps, and it does not have that loose part , but definitely the big main cap needs to be replaced as its does look blow, ill post a picture later.

That circled part looks like an inductor NOT a capacitor.
yeah i think it is, but it only had broken solder, which after i fix them the chassis worked, but with a flaw image, ima do a full cap restoration, and hope that fixes the image. I just need to know the equivalent to the c225 yellow cap.
You've probably already cleaned it up, but it looks like some solder splatter from the overheated coil may have shorted the 2nd and 3rd traces below L301.

Even if your multimeter shows no short between the traces, microscopic solder globules can create an arcing short-circuit path when power is applied and more current/voltage is passing through the traces.




Scott
Yeap i fixed that since day 1 , and the chasis turned on with a bad image, you can see that in the video i uploaded on the previews comments, now I just need to know the equivalent to the c225 yellow cap. as im gonna do a cap kit on the chassis.

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Re: Chinese Chassis , need help.
« Reply #14 on: March 25, 2020, 12:28:02 am »
c403? is more in line with the yellow cap.

abispac

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Re: Chinese Chassis , need help.
« Reply #15 on: March 25, 2020, 09:53:22 am »
c403? is more in line with the yellow cap.
you know what i replaced the whole cap kit and i had the same result, plus the monitor had a green color on one corner and i didnt like it, i give up on this one, today im gonna have it replaced for a working one. so ill just get back here when iget the other monitor, on the other hand, i updated the no iso topic, turns out its a very common monitor, and should be an easy fix , today ill se if i can replace the parts ,if im lucky , ill see if i can get the iso, and hope i can have 2 working monitors by the end of the day. Thanks for your help lilshawn

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Re: Chinese Chassis , need help.
« Reply #16 on: March 25, 2020, 10:58:39 am »
What in the hell are you trying to accomplish? How many monitors are you trying to ---fudgesicle--- up all at the same time?

Try working on one at a time. Slow down.

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Re: Chinese Chassis , need help.
« Reply #17 on: March 25, 2020, 12:33:28 pm »
 :laugh2:
What in the hell are you trying to accomplish? How many monitors are you trying to ---fudgesicle--- up all at the same time?

Try working on one at a time. Slow down.
:laugh2:
I guess you are right, thats gonna happen today, as i say, te chinese one, i got tired, i dont think its worth the time, ill just exchange it for a working one which i will pick up today later on. On the other hand, ill just buy the broken parts for the other monitor, the one thats very common and easy to fix and hopefully ill find an iso to put it to work as well.

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Re: Chinese Chassis , need help.
« Reply #18 on: March 25, 2020, 12:36:50 pm »
You are a good sport. I really mean it when I say slow down. It will help.


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Re: Chinese Chassis , need help.
« Reply #19 on: March 25, 2020, 12:46:19 pm »
Abispac is good peeps. Still in the mota business, bro?
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