How can I test non-polarized capacitor?

[Hitto]

About the specific capacitor where the OP asked on the starting post, there's a topic where the matter is mentioned: https://www.badcaps.net/forum/genera...ing-capacitors

That capacitor has to handle at least 5-6 Amperes in the 3.3/4.7uF variant. I suppose much more in this case since the capacitance is quite higher. Any direct replacement is out of production since at least the second decade of the 00s but nowadays we have MKP capacitors which are miniaturized enough to fit and are able to do the job much better than an electrolytic (since we're talking about high frequencies, read below).

You can replace it with a MKP capacitor of a good brand (such as Panasonic) and you can use without any problem a similar (or slightly higher) capacitance. What you have to take care is about derating: use a capacitor of 100V or more since that specific capacitor will have not only to handle a lot of current but also a very harsh one (a 15KHz sawtooth waveform). Any generic nonpolar capacitor (but also any cheap MKP capacitor) will fail badly in a matter of seconds because of the very high current requirement and failure on that part of the circuit means cascading damage on nearby transistors and circuitry.


About B+, it can be low if capacitors filtering it is/are dry. A sign of problems about B+ voltage being too low is low brightness or shaking picture while increasing it. I would replace all of the capacitors of the same brand which you currently found as defective as they will soon fail in the same way.

It is very difficult to purchase LG 154-179M FBT at the present and Its cost is insanely expensive in ebay..
How can I cover permanently the position where leak tiny arcing from the thickest wire of Flyback transformer?

You can use epoxy but everyone say that leakage will find a way again some months later so it seems to be a temporary repair.

Some FBTs have removable wires but you have to slightly push the wire and there is no guarantee that it will indeed come out. Some Italian TVs had this feature because back in the day as it was a recurring problem (even dust can cause arcing so cleaning the base of that pin was crucial, they were serviceable easily). That spot in the clip you posted may be easy to cover with epoxy (I have a similar problem on a PC CRT but the point is very hard to cover and it happens not frequently, 99% of the times it will become worse to the point of causing damage or triggering protection on the secondary side).

[chth96]

A week ago, I noticed that

It sounds very weird loud noise from anode cap and Flyback transformer!!!

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...

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/w5w81...=otprket8&dl=0

I have checked that most of crucial components(film capacitor,electrolytic capacitor,transistor) and its adjacent components near FBT has good continuity for each other. and I confirmed that there was no crack on the all pin of FBT.

But when I tested it in darkness and in bright in turn,I finally found that there have been leakage in the thickest wire of Flyback transformer.
(You can confirm from below video that there is a dim light in darkness which is locate in the position of the thickest wire at the bottom)

https://www.dropbox.com/scl/fi/8kc0c...=zciveo6o&dl=0

and I also recorded it at close range,You can obviously confirm that there is tiny arcing from the thickest wire at 0:25
https://www.dropbox.com/scl/fi/yqggr...=vxjio3fc&dl=0

It is very difficult to purchase LG 154-179M FBT at the present and Its cost is insanely expensive in ebay..
How can I cover permanently the position where leak tiny arcing from the thickest wire of Flyback transformer?

[chth96]

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.



https://www.dropbox.com/scl/fi/nf89j...=kwp7a3gx&dl=0

https://www.dropbox.com/scl/fi/kpygfjos5nj6c0zmjzqjg/20240710_163404.jpg?rlkey=a1pdfx2nlk7vwr4vj5zvz5u0h&st=i0v7dzp3&dl=0

https://www.dropbox.com/scl/fi/013nycsv4uyuxup3yxzjn/20240710_163337.jpg?rlkey=0lgkfgn0mtsasskg6nijljxv7&st=tfbu3gby&dl=0

https://www.dropbox.com/scl/fi/qz1l92pcb2vveac77ce31/20240710_163326.jpg?rlkey=2pr4tom4sxoi7r40x0bp8cd6h&st=7bkdcc2y&dl=0



https://www.dropbox.com/scl/fi/3b8ir14tlw0jsrkj3w1me/20240710_163525.jpg?rlkey=vskgy1zefjf4kd5n8p9mqj1sd&st=3e5hkff3&dl=0

https://www.dropbox.com/scl/fi/q469a...=d8y0cvfh&dl=0

It seems that there is smaller noise than yesterday.

https://www.dropbox.com/scl/fi/59tfi...=50r20xsr&dl=0

[stj]

it must have the ajustments in the eeprom, hopefully one of the linked manuals explains the button sequence to get into the service menu
some tv's even have an option to lock the frequency (region locking) or to auto-switch.

[R_J]

50Hz/60Hz does not change sync polarity, he's just got the sync ajustment a bit tight so it wont lock-on.
only VGA connectors change sync polarity with resolution or frequency.
the only thing you can do on SCART is change the input from widescreen to 4:3 by changing the voltage on the mode pin.

It looks like the sync polarity is not the issue but there is no vert hold adjustment on this chassis, I wasn't sure how he had the box connected to the tv

[stj]

The problem is with your source, it is likely changing the video output signal resolution and sync polarity when the game starts, this tv is not meant for that. it is not a multi standard tv

50Hz/60Hz does not change sync polarity, he's just got the sync ajustment a bit tight so it wont lock-on.
only VGA connectors change sync polarity with resolution or frequency.
the only thing you can do on SCART is change the input from widescreen to 4:3 by changing the voltage on the mode pin.

[R_J]

Make sure the crt aguadag coating on the crt (the black coating on the outside of the crt glass) is grounded to the chassis It sounds like a ground might be missing, this is just the high voltage bleeding off it will not burn out or burst the crt.

Post a couple pictures of the rear of the tv so I can see the grounding on the crt and how the ground strap connects to the chassis. I tried looking up the model number you provided but it does not seem to exist

[chth96]

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.

https://www.dropbox.com/scl/fi/zp4zw...=wc083ly5&dl=0

When I switched on TV,I confirmed that It display screen like yesterday,But Now I heard quite loud noise from anode suction cap and cpt board like below video.I recorded below video when I closed all of window in order to reduce noise from outside.

https://www.dropbox.com/scl/fi/z8778...=t5vmvk79&dl=0

Although It was noiseless almost as soon as I unpluged ac cable,But I really dread of this loud noise may cause burnout or burst of cathode-ray tube or CPT board itself.

[R_J]

The problem is with your source, it is likely changing the video output signal resolution and sync polarity when the game starts, this tv is not meant for that. it is not a multi standard tv

[stj]

check the soldering on the neck board and make sure the earth wire between the tube and neck board is o.k.
the 50/60Hz thing can probably be fixed by ajusting the vertical hold.
not sure on that tv if it's a variable resistor or something in a service menu though.

[chth96]

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).

So I soldered these pin and There was no more distorted screen and silent while pressing channel up or down button!
But Unfortuantely,There still remains minor issues which seems to be extremely hard to repair.

The first is not able to display flickering screen when I play retrogame in 50Hz mode.

As this 29 inch CRT TV(CN-29H3) only supports 60Hz mode, It must display flickering screen like below video which I recorded from working 5 inch CRT TV.
20240708_092329.mp4 (dropbox.com)

But It(CN-29H3) displayed black strip at the top and won't display any flickering screen like below video
20240708_092613.mp4 (dropbox.com)

And I heard noise of Electricity spark nearby its anode suction cap and cpt board like below video.
20240708_102545.mp4 (dropbox.com)
Although,It is not aloud noise at all, but rather somewhat low noise.But It seem that this noise lasted 5-10 minutes after I unplugged its ac cable.

And When I plugged its ac cable and switched on, It display somewhat blur image for 2-5 minutes ,especially it is very blur in the menu screen,I think that it is the most annoying issue.
Besides,I think there is blur effect on the edge of letters or characters in the screen.
But all of below screent was taken when I made use of composite cable,So I doubt that was the way it was supposed to be done

https://www.dropbox.com/scl/fi/0re2e...=cgns0y95&dl=0

https://www.dropbox.com/scl/fi/61q9j...=u1z3uhn3&dl=0

https://www.dropbox.com/scl/fi/duzzi...=3hdek47p&dl=0

https://www.dropbox.com/scl/fi/dl6h1...=mk8nfnsu&dl=0

[R_J]

Did you reinstall the original C433 (5.6µf/50vBP) capacitor? or did you use a replacement? Check connections around Q406~Q408 and the two adjustments vr400, vr401 (pincushion and horz. size circuit) it may be a dirty control or there may also be a weak elec. cap in that area as well.
I would resolder Q408, its connections don't look good from here.
Another electrolytic that can cause problems in these chassis is C406 (2.2µf/160v) horz. drive transformer filter cap.

[sam_sam_sam]

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 IC ,So there would be minor crack on its solder joint.

I soldered all pin of IC01(LG8708-08A), IC201(GL3812),IC501(TB1231N) and Turner TU101(TUSHB-A07A) at the bottom of PCB, and It finally displayed screen!

But there is some weird issue for this CRT TV.

If I frequently press channel up or down button It sometimes make it mute like below video.

https://www.dropbox.com/scl/fi/d667w...=ralpc4qj&dl=0

And Display suddenly become distorted(concave), after switch on CRT TV in 10-20 minutes.

https://www.dropbox.com/scl/fi/v2qdo...=3ksy8xoi&dl=0

I doubt that there is still loose contact somewhere in the bottom of PCB..

I would recommend that you use a magnifying glass and very carefully check each and every soldering joints for bad soldering joints because if you found some there might be others that you could not see with the naked eye I have been there and done this before trust me check them with a magnifying glass to make sure that this not an issue that still exists

[stj]

check the soldering on everything mounted to a heatsink,

[sam_sam_sam]

maybe - try it

One thing I would add is check the voltage on the led light side of the device to make sure that it is in the range of voltage that is needed for the device to work properly and make sure that control side of the device is within the range of the original device that is in the device now that you are working on

[chth96]

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 IC ,So there would be minor crack on its solder joint.

I soldered all pin of IC01(LG8708-08A), IC201(GL3812),IC501(TB1231N) and Turner TU101(TUSHB-A07A) at the bottom of PCB, and It finally displayed screen!

But there is some weird issue for this CRT TV.

If I frequently press channel up or down button It sometimes make it mute like below video.

https://www.dropbox.com/scl/fi/d667w...=ralpc4qj&dl=0

And Display suddenly become distorted(concave), after switch on CRT TV in 10-20 minutes.

https://www.dropbox.com/scl/fi/v2qdo...=3ksy8xoi&dl=0

I doubt that there is still loose contact somewhere in the bottom of PCB..

[chth96]

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.

[chth96]

What is the voltage across C812? it needs to be at least around 9vdc to supply the regulator transistor Q800 collector. Q800 base should measure 7.5vdc, if not ZD808 may be leaky and not zenering at 7.5vdc I would have also replaced C812

If Q800 collector is over 9v and the base is 7.5v and the emitter is only 6.4v, Q800 may be bad

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) and Its ESR value was lower(0.5 ohm) than reference value.

By the way it was written B.75 on the surface of ZD808 zener diode.
Is It Okay to purchase any zener diode which has specification of 7.5V?

[R_J]

What is the voltage across C812? it needs to be at least around 9vdc to supply the regulator transistor Q800 collector. Q800 base should measure 7.5vdc, if not ZD808 may be leaky and not zenering at 7.5vdc I would have also replaced C812

If Q800 collector is over 9v and the base is 7.5v and the emitter is only 6.4v, Q800 may be bad

[chth96]

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.