Open Circuit In Heater (Filament) Of CRT Tube
After so many CRT Monitors sent in for repair, i could say that i only came across one unit of a 14″ Acer Monitor that had an open winding in the filament (heater). The complaint was no display but have high voltage and i found that the heater was present but there was no glow in the filament. Checking the filament with an ohmmeter revealed that in fact the filament already had an open circuit internally. This is very uncommon and normally the filament is quite robust.
Do you know that our filament could take about 10 to 11 volt? A normal tube is using 6.3 volt dc and by increasing the heater voltage one can bring back a tube to life but again it depends on how severe is the tube. I had done an experiment before many years ago where i deliberately increase the heater voltage to see what voltage the filament could withstand. I tested it by using my adjustable power suppl. Increasing the voltage up to 11 volt seems to be still okay but when i set to 12 volt dc, the filament immediately break.
Now, if you ever come across any tube that have dim display and you have confirmed that the tube already weak then modify a circuit that can only go up to 10 volt. 11 volt could be marginal and the best is from 8 to 10 volt. 12 volt will surely burn up the filament. If you have the time and a bad tube (winding shorted and etc) then you can do the experiment yourself and see how is the outcome. You will see that the filament will glow extra bright before it burn out.
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zed
May 22, 2009 at 10:02 am
sir can you show me how to measure the with ohmmeter the filament area.which pin? the heater pin and what pin? thanks sir. can you show a picture how to measure it.GOD BLESS YOU.
admin
May 25, 2009 at 9:19 pm
Hi Zed,
Use ohmmeter and measure between the H pin and ground. Some Monitor labelled it as H1 and H2. These are the filament pins.
Jestine
romy
June 10, 2009 at 10:56 pm
JUNE 10, 2009
Hi Zed,
Could you furnish me an schematic diagram of a PC power supply ATX 500W together with a troubleshooting guide. Thank You Very Much.
romy
June 10, 2009 at 11:04 pm
ZED,
How long will I wait for the schematic diagram and troubleshooting guide
Akhilesh mishra
December 10, 2009 at 3:04 pm
no display in crt but E.H.T transformer is ok.
Akhilesh mishra
December 10, 2009 at 3:06 pm
Please give a tips the cheking a fault in this condition
admin
December 11, 2009 at 5:44 am
Hi Akhilesh,
Try check the heater voltage(6.3 vdc) and G2 (about 250 to 300 vdc). Missing either in one of the voltage could cause no display symptom.
Jestine
Irfan
December 22, 2016 at 1:48 pm
6.3vdc or 6.3vac?
Jestine Yong
December 23, 2016 at 7:43 pm
Hi Irfan,
CRT TV using 6.3vac and Monitor using 6.3 volt DC
Jestine
Michael Jackson
November 13, 2010 at 4:07 pm
Can We check flyback 6.3 volt without CRT, seem Flyback may bad because there has no 6.3 volt but has high voltage 27k I just bring only TV chassis and Yoke. I left CRT at my friend house. Please answer my question if CRT must be loaded to flyback will show 6.3 vol ?
admin
November 13, 2010 at 8:41 pm
HI Michael,
The TV 6.3 ac volt is a high pulse ac thus you can't test with normal multimeter. If you look at neck of the picture tube and if there is light then the 6.3 volt is present. If there is no light, it could be the flyback or the tube internal heater element had open circuit.
Jestine
DHILAN
September 28, 2012 at 1:44 pm
DEAR SIR
I HAVE TROUBLE WITH PANASONIC TV SET MODEL TC-2155R ITS SOUND IS NORMAL AND NO PICTURE I TEST HIGE VOLTAGE LOOKS OK HEATER ALSO LIGHT I REMOVE YORK COILS THEN I SEE VERY DIM SPOT IN THE TUBE I MEASURE FILAMENT VOLTAGE ITS 4.5 V AC AND K 65 V DC G 250 V DC PLEASE LET ME KNOW ABOUT THIS FAULT HOW I CAN FIND WAHTS THE FILAMENT VOLTAGE MUST BE?
THANKS SIR
Jestine Yong
September 28, 2012 at 8:30 pm
Hi Dhilah,
Please do not remove the yoke coil. Put everything back to normal and turn higher the g2 voltage to see if the re is picture or not. Tha ac voltage is a high pulse ac thus normal multimeter can't be used to test such circuit. If you see a orange light in the tube then 90% the heater is ok.
Jestine
Dimeji
July 29, 2013 at 4:21 pm
Admin please help. I have a CRT that has no glow inside tube neck when put on. There is continuous hissing sound when you power on the entire unit but no display. Tested filament pins, got 5.6 ohms. Using a Fluke multimeter, (model 87V) tested the heater terminals for voltage while unit was on, got 3.2v ac. Can you advise what to do? Is the voltage supposed to be ac or dc? Is 3.2v sufficient? Thank you.
Jestine Yong
July 29, 2013 at 7:50 pm
HI Dimeji,
Yours is a CRT TV or CRT Monitor?
Jestine
Saylu
August 14, 2017 at 8:51 pm
Hi..
Sir
My Samsung crt tv on neck board not comeings proper voltage on the H1,H2,G2,R,G,or B sir please let me answere about this fault.
Thanks sir
Jestine Yong
August 16, 2017 at 9:30 pm
Hi Saylu,
Have you checked if the power supply output voltages good and stable?
Jestine
x3k30c
September 2, 2013 at 7:19 am
Great blog mister!
I have a MAG DX700t monitor, trinitron tube. Filament voltage is 6.3v (measured with DC) resistance is around 3.2-3.4ohm orange light exist. High voltage seems to be ok though I couldn't measure it. (a main-board test point should give 500v, yet it 450v at full setting - high crisp sound and disperse blue plasma around the tube I think anode voltage is ok)
G2 is 360v DC, G1 is -90v DC (?), HOT seems to be ok, yet there is no display.
Once, tried to disassemble the neck of the tube (deflection etc.) but half-way I stopped, there were the RGB dots on the middle of the screen only for a while after the unit is switched on. (I forgot to attach some wires)
G2 doesn't change when the pot is adjusted on flyback. flyback of tube defect?
Jestine Yong
September 2, 2013 at 10:25 am
G2 voltage must change when you turn the flyback knob. Try trace from the G2 wire to see if there is a resistor open circuit or not.
Jestine
x3k30c
September 2, 2013 at 7:54 pm
Hi Jestine,
thanks for your comment! but i think i might have killed the flyback. There was a blue wire coming from near the flyback and as far as i remember it was connected to the chassis ground so i connected. /there were something on the display but the relay ticked for a while and everything gone. now the led is blinking when the flyback is connected. voltages ok when flyback is removed/
Sorry for the slight off comment
THANK YOU FOR THIS SITE
solomon eshete
October 15, 2015 at 9:48 am
Hi Mr Yong! I've the same problem with my 21 inch jvc tv set as the above question. My set starts the sound for a very short period of time and then stops and off timer led starts to blink,no sign of the heater or display on the screen.How could I correct it?
Jestine Yong
October 15, 2015 at 9:30 pm
HI Solomon,
First thing you need to check if the power supply producing good and stable voltage or not. If yes, make sure the 5 volt is going to the cpu ic vcc input. Next make sure no shorted components in the B+ supply line and the HOT is good.
Jestine
solomon eshete
October 16, 2015 at 3:19 am
Hi mr. Yong! A 35v,1000microfarad capacitor in a 21-inch JVC TV set circuit board explodes every time I replace a new one & put the power on. I need help,Sir.
Jestine Yong
October 16, 2015 at 8:43 pm
HI Solomon,
It could be due to bad quality of cap or the dc voltage too high.I suggest that you check the dc voltage and it should not more than 35 volt.
Jestine
solomon eshete
October 27, 2015 at 5:55 am
Hi Mr Yong, a CRT TV set when put on,its heater tries to start the filament and stops after showing a white light,I need your help Sir.
Jestine Yong
October 27, 2015 at 7:02 am
HI Solomon,
Is the high voltage from the flyback still present?
Jestine
solomon eshete
November 10, 2015 at 6:14 am
Hi Mr.Yong ! The shorted voltage that was burning capaciters and IC transistors is solved now,it's filament shows a white light and stops when I switch it on. Shall I adjust the screen knob at the flyback to increase the G2 voltage?
Jestine Yong
November 10, 2015 at 10:31 am
HI Solomon,
A working filament should light up and you can adjust the G2 voltage to get the right brightness you need.
Jestine
Solomon Eshete
November 25, 2015 at 9:20 pm
Hi Mr. Yong, What could the real cause a blurred image display of a TV set after a damaged IC transistor is changed? I'm grateful to you Sir.!
Jestine Yong
November 27, 2015 at 9:29 am
Hi Solomon,
Blur display is usually caused bad flyback or pc tube. Try adjust the flyback focus knob first and see how it goes.
Jestine
ABRHAM
February 18, 2018 at 11:18 am
Hi ser I have a problem with jvc crt tv modle no.AV14FMG3G
No light at the heater
Arnold
December 12, 2015 at 8:57 am
Hi sir jestine.
How many ohms of each RGB filament of CRT TV 21inch
Thanks.
Arnold
Jestine Yong
December 12, 2015 at 12:22 pm
Hi Arnold,
There is usually only one filament and it should be about 4 to 7 Ohm.
Jestine
Jodi
February 25, 2016 at 5:26 am
Hi...I recently picked up a sony pvm-2530. It is missing red and blue, but shows green images...and they are dim. If jumper with 10k resistor to ground, green goes brighter...jumper to red or blue..nothing. Transistors for rgb on neck board all show same voltage. And voltage at rgb pins show 65-70vdc
Jestine Yong
February 25, 2016 at 10:25 am
Hi Jodi,
Probably the two guns could have been very weak. Try visit the link below and read through it as there is a way to brighten up the tube:
http://www.repairfaq.org/samnew/tvfaq/tvncbwp.htm
Jestine
Jesse torres
March 8, 2018 at 9:55 pm
Hi sir,is it correct that the rgb supply voltage in crt is 180 vdc?thanks in advance.
romel
July 9, 2016 at 3:57 pm
Mr Jestine hi there! How could i know that the H.O.T in tv is faulty? Pls give advice admin...i am very grateful 2u sir
Jestine Yong
July 11, 2016 at 10:04 am
Hi Romel,
You need to remove the HOT and test it with your ohmmeter.
Jestine
Jayandhran Seenandan
July 16, 2016 at 2:49 am
Hi I hav an Akashi cxrt tv. I got I t working. The problem is the colur is black n white on start up , but if u shake the board the colour cums. I suspect a dry joint , but I canot find it. Please advise. Thank u.
Jestine Yong
July 16, 2016 at 10:06 am
Hi Jayandhran,
Try resolder the IC and crystal oscillator area.
Jestine
girmachew
September 3, 2016 at 11:41 am
My name is girmachew
I have a superfine crt tv
When I turned on it takes several minutes what should I do
Jestine Yong
September 5, 2016 at 10:58 am
HI Girmachew,
It can be due to weak tube or the G2 voltage not high enough. If G2 voltage is not high enough, it can be due to bad flyback or the G2 line have leaky component or even decayed glue.
Jestine
Benjamin D
September 3, 2016 at 2:48 pm
Hello sir, I was looking through a 29" KONKA CRT TV, it suddenly stops, there is no orange light on the CRT tube or no high voltage on the anode although the HOT is changed. Is that a detective flyback? I need your support sir.
Thank you
Jestine Yong
September 5, 2016 at 11:32 am
Hi Benjamin,
You need to check if there is pulse to the base of HOT or not. If no pulse then the flyback will not be energized.
Jestine
johhn alex
September 30, 2016 at 9:17 am
hi sir yong can you please help me in jvc av21va15 no power continues blinking only..complete b+ and other supply as i check the voltage..i replace vertical ic caps and HOT i also done resolder.need your advice or schematic diagram for this unit.tnx
and God bless
Jestine Yong
October 2, 2016 at 4:29 pm
Hi John,
Sorry i do not keep schematic. Have you isolate the B+ line? Blinking can be caused by power section or failure in high voltage section.
Jestine
johhn alex
October 2, 2016 at 5:52 pm
hI sir yong,
The b+ supply is normal and there is oscillation but the protect circuit keep the unit shutoff after few second.Can i bypass the protect sir OR do you have any suggestion regarding this problem.
thx
john
Jestine Yong
October 5, 2016 at 9:39 am
HI Johhn,
You cannot bypass the circuit-it is too dangerous as the high level of Xray can harm the user. You need to find out the fault why it shutdown. Can it be caused by the power supply itself or the high voltage circuit like a broken flyback transformer.
Jestine
Sfiso
October 8, 2016 at 6:44 pm
Hi jestine
My tv has a display problem, there is no red on screen I have blue and green but red is very dim, I tested power on the pins there is voltage on all three Red, Green and blue and no dry solder voltage is around 169 DC, everything works fine only red is very dim and I adjusted the colur settings no change... TV is SINOTEC 54cm
Jestine Yong
October 8, 2016 at 10:34 pm
Hi Sfiso,
Red dim can be due to weak red gun or bad capacitors in the CRT board.
Jestine
Amandeep
November 29, 2016 at 12:02 am
Dear Sir
Warm greetings of the day
My tv have display problem. There is only contrast problem.
From the service menu i have adjusted the BW balance and increased the contrast. But still picture is Dim. Kindly give a suitable resolution.
Jestine Yong
November 29, 2016 at 8:18 am
Hi Amandeep,
Picture dim can be caused by weak picture tube. If the G2, g1 voltage check to be good and heater have a bright light then most probably the tube is weak. However, sometimes it can be caused by failure in the contrast circuit or even bad eeprom ic data.
Jestine
dodong
December 24, 2016 at 3:10 pm
sir jestine
is there other ways to make the crt tv sharper image cause i already adjusted the full clockwise, the image is still blurred. Thanks
Jestine Yong
December 25, 2016 at 7:27 pm
Hi Dodong,
If adjust the flyback screen focus still can't make it sharp then the tube have problem.
Jestine
Varun Sharma
December 28, 2016 at 11:01 pm
There is no heater glow in my CRT TV. What to do sir how could i repair it... ??? Actually i accidentally shorted the 180 terminal and the heater terminal on the CRT PCB. after that there was no display.Please help me solve this problem.
Jestine Yong
December 30, 2016 at 12:32 pm
Hi Varun,
The flyback has to work first in order to see the heater light. Have you checked if the flyback is receiving the B+ voltage and a waveform to the base of HOT? If the flyback don't work there will be no display.
Jestine
Denver
September 27, 2018 at 9:04 am
hi my name is Denver I have a 29" Telefunken tv the heater goes on then off what can it be
Jestine Yong
September 28, 2018 at 10:02 pm
Hi Denver,
Probably there is a dry joints in the heater circuit. You can trace backward from the heater to the source and see if there is any dry joints along the circuit line
Jestine
Manen
February 3, 2017 at 5:37 pm
Hi Mr yong,
I have a 21 inch crt tv with the picture problem, so i try to checked heater voltage and i got it only 1 volt ac. Is it normal?
thank you
Jestine Yong
February 4, 2017 at 10:35 am
Hi Manen,
TV heater voltage is high frequency ac so your normal multimeter not be able to check it. If you can see an orange light in the tube probably there is an ac voltage.
Jestine
Mina
February 27, 2017 at 2:46 am
hello
i have compaq 7500 monitor the problem is no display
i check the voltage on heater found G1 =-27
and G2= 270
and HOT okay but it be hot fast when i turn on monitor
i think i have a problem in G1 please help me to solve this problem
Jestine Yong
February 27, 2017 at 7:57 am
Hi Mina,
What is the heater dc voltage? Have you tried increase the G2 voltage to 300 vdc?
Jestine
Mina
February 27, 2017 at 10:19 pm
it's 6.7 volt and i tried to increase volt of G2 to 285 volt but Hot transistor become very hot in short time
Jestine Yong
February 28, 2017 at 7:27 am
Hi Mina,
Ok noted. When you adjust the brightness did the G1 Voltage vary? Is there a resistance when you measure the heater filament voltage?
Jestine
Mina
February 28, 2017 at 5:20 pm
The G1 don't vary
which resistance ?!
Jestine Yong
March 1, 2017 at 3:34 pm
Hi Mina,
You have to track from G1.It can be resistor problem, leaky transistor, bad capacitor or even corrupted eeprom ic data.
Jestine
Mina
March 1, 2017 at 6:02 pm
i found two track to G1 on monitor one on the main board and another in socket of the CRT
but i think found another problem cause the HOT be more hot in short time
can u help me by monitor circuit
Jestine Yong
March 1, 2017 at 9:23 pm
Hi Mina,
Sorry I do not have monitor circuit.
Jestine
Mina
March 2, 2017 at 4:54 am
MR young how i measure the volt of line oin 3&4&5&6&7&8&9&10
ac or dc and i think there is short between 3&4&5&6&8&10 this pins and the ground
this natural ??!
Jestine Yong
March 7, 2017 at 8:15 am
Hi Mina,
Sorry i don't understand your question. Can you elaborate?
Jestine
Nader
March 8, 2017 at 2:20 am
hello
how can i measure the volts of power transformer
how i can measure it by put voltmeter on Ac or dc and put the black electrode and red electrode on what to measure the power volts of the transformer
and what the value of this volts for CRT monitor 17 in
randy dolot
June 8, 2017 at 9:53 am
Sir lg CRT tv 21 if you float the fuseble resistor of heater it doesnt shutoff if you connect it will shutoff.where is the trouble pls help me.
Jestine Yong
June 12, 2017 at 10:04 am
Hi Randy,
Power shut off wit no power Led light or the display/raster shut off?
Jestine
Daniel
June 29, 2017 at 2:46 am
Hi, i need to change the control of a CTR monitor and use another source. I'm glad if someone helps me.
Daniel
July 13, 2017 at 12:58 am
Hi, I need to change the control of a CTR of my monitor, how can i do it? I mean, i understand that i need 3 sources to source that can replace the fly back and 2 more one for heater and another for focus and the colors ... is it possible? It is for a experimental subject of my university
Jestine Yong
July 14, 2017 at 10:08 am
Hi Daniel,
May i know what kind of control do you want to change in your CRT Monitor?
Jestine
Akbar Gondal
October 17, 2017 at 5:16 pm
Salaam,
Brother Jestin i have repairing shop in Pakistan .
One LCD Sony model number 40BX400.There is sound ok but no picture or display.can chang channals.can you help me to resolve this problam ?
Thanks
Regard
Akbar
Jestine Yong
October 17, 2017 at 9:11 pm
Hi Akbar,
It could be the T-con board controller IC fault. Without hands on assessment I would be really guessing on what might be wrong. I wish I could be of more help.
Jestine
Murali
November 25, 2017 at 6:48 pm
Hi sir
I have crt tv, there is no display but eht from flyback is ok. No Orange lights in tube. Is there problem comes with flyback or butI did not measure the heater voltage. Filament measures 4ohms. There is no leaky componenets and dry joints around all circuits. Kindly help me sir
Regards Murali Chennai Tamilnadu India
Jestine Yong
November 27, 2017 at 10:12 am
Hi Murali,
Yes, the heater voltage of 6.3 volt ac comes from the flyback. With normal meter you may not be able to measure it. You need a meter that can handle the high frequency ac voltage to check it. If the heater filament is good and there is high voltage from the flyback then chances is high the flyback is the cause of the problem.
Jestine
kishore
December 14, 2017 at 3:42 pm
Hi sir,
I have one problem . My TV is Samsung CS29MA21.
No Video but audio works. The video is completely black.
The heater doesn't glow bright. heater glows very low.
I tracked the heater wire till flyback transformer. there was only 1 resister in middle and its good.
The Voltage at the PCB in CRT is 202Vdc,
TheVoltage at the Heater pin in CRT Board is 3.2Vac when the pcb board at CRT connected with CRT.
TheVoltage at the Heater pin in CRT Board is 6.2Vac when the pcb board at CRT NOT connected with CRT.
The Voltage at input of Primary transformer at capacitor is 300Vdc.
The Voltage at secondary of transformer is 130Vac, 12Vac and 6 Vac.
The voltage at Secondary transformer across capacitor is 130Vdc
The flyback transformer is working, at primary of Flyback the voltage is 130Vac, Switching takes place at Horizontal IC.
I am getting voltage at secondary of Flyback Transformer.
I am geting Voltage arc in Anode of Flyback transformer when i removed the anode separately and checked.
I am getting 5vdc to the main IC and E2prom.
to fix the problem i tried changing the Video IC in CRT board, I changed Horizontal IC and driver trainsistor.
I also changed the vertical IC.and also main control IC, but still there is no video.
What will be the problem, The heater glow very very low.
Flyback details:
FLY BACK Transformer
pin 1-3-4 short
pin 5-6-7-8-9-10 short
pin 1-2 => 232vac
pin 1-3 => 465vac
pin 1-4 => 506vac
pin 5-6 => 78vac
pin 5-7 => 69vac
pin 5-8 => 32vac
pin 5-9 => 133vac
pin 5-10 => 78vac
pin 6-7 => 0
pin 6-8 => 28vac
pin 6-9 => 30vac
pin 6-10 => 0
pin 7-8 => 14vac
pin 7-9 => 42 vac
pin 7-10 => 0
pin 8-9 => 122 Vac
pin 8-10 => 43 Vac
pin 9-10 => 72 Vac
Jesse torres
March 8, 2018 at 10:14 pm
Mr. Jestine.i have my 21" jvc musee intere Art crt,the problem is after 20 minutes while the tv set is On it will automatically shut off and back in normal operation after a seconds and totally shut down,with the power blink.Hope you can help me to solve this problem.Thanks in advance..
Jesse torres
March 9, 2018 at 4:41 am
the power led dislay continuos to blink
Mahmoud
April 16, 2018 at 8:02 pm
Hello sir
My 29" samsung crt has a problem ... The heater and ground on the scart that going to screen are open on ohmmeter.. also on flyback the heater pin + the ground are open ..? While i just change the flyback and discover the fault is the same with the new one even .. also there is a shark light happen on screen pins inside everytime i work it
Prem
April 26, 2018 at 11:57 am
My lg crt tv automatically shout down after few second what could be the fault.when on for few second screen seem good appear like normal tv.
Angelo
December 6, 2018 at 9:46 am
Sir pls help,sonny triniton.no picture sound ok,but after 3-10 minutes the video is ok,but when the video was missing the line of 9v-9v,R-mv,B-mv,G-mv and the pin of tube to the bord KB-208V,KG-207V,KR-207V its very high reading after 3-10 minutes when video is back the new reading of line of 9v-9v,R-2.5V,G-3.2V,B-3.2V and KR-117V,KG-77V(sometimes its become 100+v)KB-83v(sometimes 100v+) G2 supply is ok,B+ is ok please sir answer me.thanks
Jestine Yong
December 13, 2018 at 5:48 pm
Hi Angelo,
Have you checked if the power supply output voltages are good? Have you checked/replaced if the video pre-amp IC is good? If the CRT Board voltages are good then track from the RGB back to its IC.
Jestine
Asad Ali
February 21, 2019 at 12:50 am
hillo sir
....my tv circuit is ok but in picture tube heater doesnt work ...and doesnt show the red light in filament....is this possible to repair the heater?????
Jestine Yong
February 21, 2019 at 7:31 am
Hi Asad,
Filament voltage for CRT TV comes from flyback and is a high frequency AC volt. Your normal meter can't measure it. If the filament in the tube is not open circuit and if the flyback is generating high voltage, this means the flyback winding that supply the filament voltage could have open circuit or even there could be a break in the protection resistor causing no voltage going to the filament. For more info about CRT TV repair you can get Humphrey's ebook in the below link. He has vast experience in crt tv repair and it comes with his personal support to make you a good tv repairer
http://www.electronicrepairguide.com/crt-tv-repair-ebook.html
Jestine
Richie
March 15, 2019 at 8:39 am
Hi mr yong im one your follower i will just ask about 21" crt tv panasonic no power indicator no sign of life when i switch on i can measure b+ 130 then slowly decrease until 25vdc what are the culprit?
jerom
May 25, 2019 at 6:17 pm
good day sir any advise on crt tv no video but sound is good and the screen is white, all voltages in G2,RGB,H is good.i try replacesing the system ic but still no video or even the menu display thanks in advance
Frank
March 31, 2023 at 7:09 pm
Hello sir,
I can hear the 'cha' sound when I turn on the tv. All voltages are okay except the G2 and heater voltages are not present at the vet neck board and the filament doesn't glow. Any help please