Why Horizontal Output Transistor In CRT Monitor Get Shorted?
There are many reasons why the horizontal output transistor (HOT) shorted in CRT Monitor. Here are the possible cause:
HOT have life span-it can work for many years but out of a sudden it can just go shorted. Replacing only the HOT solved the probem!
Dry joints in nearby area- Yes, dry joints in the HOT leads, flyback transformer, horizontal driver circuits could cause HOT to blow.
Shorted flyback primary winding. I came across lots of HOT failure due to shorted primary winding in flyback transformer. One of the best example was the HP 17″ 7500 CRT Monitor. Not only it blow the HOT, the B+ coil and the B+ FET blown as well!
Shorted or open internal capacitor in flyback transformer. These problems has contributed lots of HOT failure in CRT Monitor. Normally i will check the internal capacitor first before i replace the HOT and switch “ON” the Monitor.
Too high B+ voltage- A higher than normal B+ voltage will kill the HOT instantly. Make sure the B+ is supplying the right voltage to the primary winding of flyback transformer.
Running at wrong frequency- I once came across the horizontal driver circuit area was running at different frequency. It suppose to run on a 31.5 Khz (depends on resolution in your CPU setting) but this faulty Monitor run at a too low frequency killing the HOT after “ON” for few hours!
Bad electrolytic capacitor in the supply line to horizontal driver transformer- If you found a HOT shorted make sure you check on this capacitor otherwise you may get a call back from your customer saying the Monitor not working again. The capacitor usually developed high ESR value that destroy the HOT in few hours to few weeks time.
Shorted horizontal yoke coils- A shorted horizontal yoke coil could instantly kill the HOT. I always use the dick smith flyback tester to confirm first that the yoke coil is good before the replacement of a new HOT.
Safety capacitor value out- If this safety (holddown) capacitor value dropped to zero, the high voltage produced at the anode could shoot up to over 30 kilo volt thus killing the HOT in a split of seconds.
Wrong replacement-The Monitor could be repaired by someone else and they had fitted a different specification of HOT thus making the HOT won’t perform the best and breakdown after certain of time.
Nearby components- There are some possibilities too that the bad components nearby the HOT could cause the HOT to blow. Check the surrounding components before you switch “On” the Monitor.
Well, hope you can absorb these tips and start repairing CRT Monitor or TV with more confident! Have a brilliant day!
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Henjo
May 7, 2008 at 5:10 am
Dear Jestine,
Thank you for the information above i really appreciate your teaching.
The problem for me is i don't really know how to locate and the B+ circuit in a TV board.
Can you please give me some information on how to identify and locate the B+ circuit on a TV (which part of the board).
your help will be very much appreciated.
kindest,
Henjo
ibrahim
May 7, 2008 at 2:11 pm
will tda4858 be a subtitute of tda4859
Jestine
May 7, 2008 at 3:05 pm
Hi Ibrahim,
The TDA4858 is not same as TDA4859.
Jestine
Jestine
May 7, 2008 at 3:08 pm
Hi henjo,
Look out for the output supply line that have the output of about 110Volt. If you are not sure you can look at the filter capacitor that was rated as 47 to 100uf 160 to 200 Volt. Follow that line and eventually it will reach to the B+ pin of the flyback. Rememeber, without this B+ voltage, the flyback would not work!
Jestine
ANAND PAWAR
May 26, 2008 at 10:51 pm
THANKS, U ARE GREAT TO SUPPORT EACH .I HAVE LG 15" MODEL-500G,IT'S HOT NO:J6810 GET SHORTED EMIDIATLY WITHIN SECONDS. WHAT SHOULD BE PROBLEM ?
admin
May 27, 2008 at 7:38 pm
Hi Anand,
You have to check it yourself as all of the suggestion above could cause the HOT to burnt the moment you switch "on" the Monitor. That means make sure the circuit is okay before you turn "On" the Monitor to save your HOT.
Jestine
guile
October 29, 2008 at 1:12 am
i have a HCL 15" monitor. It have problem from 2 months that it's horizontal display is stretched and it's buttons for increasing & decreasing size of screen are also not working properly. please help me for this problem.
You can mail me the solution at sagat221@gmail.com
thanks
Guile
admin
October 29, 2008 at 10:47 pm
Hi Guile,
It could be the pincushion/horizontal size transistor shorted. This transistor is normally attach to heat sink and is nearby the flyback transformer. The part number usually started with B649A, D669A, C2800 and etc. If the transistor tested okay then i guess you have to check all the corresponding components.
Jestine
leonard williams
September 4, 2009 at 7:58 am
my panasonic m wave runs for a while then a code number comes up on display h 98 it does not heat can you help me what cause that problem
admin
September 4, 2009 at 12:34 pm
HI Leonard,
Sorry i do not have information for this.
Jestine
adhi
October 2, 2009 at 4:38 pm
do running tv set with horizontal yoke disconnected cause any problem to the board?
admin
October 2, 2009 at 7:13 pm
Hi Adhi,
It depends on the TV. I had burnt the HOT before without connecting the yoke coils.
Jestine
kaminder
October 24, 2009 at 2:07 am
I have Lg 500g model monitor.my monitor goes in standby mode when i attach the VGA cable in cpu, when i remove the vga cable from cpu then monitor show no signal connection message on the screen with RGB signal box .pl give me the right solution for this problem
admin
October 24, 2009 at 10:13 am
Hi Kaminder,
First make sure the signal cable H and v signal is present to the input of CPU. If both signals present then check on the cpu supply voltage and make sure it is within range (usually 5 volt). Check to see if there is crystal oscillator waveform present at both the legs of the crystal with scope. If all check to be ok then possibly the fault is in the CPU or a corrupted eeprom ic.
Jestine
tirta
November 26, 2009 at 3:35 pm
sukses selalu justine,
terimakasih untuk semua informasi pada website anda.
saya ingin bertanya tentang IC MIP 2F2 pada tv LCD Toshiba 32" yang terbakar. ( rangkaian power supply )
1. Apa persamaan/equivalent dari IC MIP 2F2,karena didaerah saya komponen ini tidak ada dijual.
2. berapa persamaan/equivalent FBT ( TPV79A355-503)pada CRT HP 14' dan
berapa persamaan/equivalent FBT ( tfb-7016/LCECF-1707 )pada CRT IBM 17'.
ke 2 FBT ini tidak ada dijual in my city.
terimakasih atas jawabannya.
tirta
admin
November 26, 2009 at 7:49 pm
HI Tirta,
Maaf kerana tiada informasi tentang part nombor LCD TV tersebut. Untuk gantian flyback, saya cadangkan anda melawat http://www.hrdiemen.com kerana di negara ini, flyback adalah sukar untuk didapati.
Jestine
SUKA RANJAN
December 19, 2009 at 11:08 pm
GOOD AFTERNOON sir
what is defination of scl &adl
admin
December 22, 2009 at 11:18 am
HI Suka,
Scl means clock line and SDA is data line. I'm not sure about adl.
Jestine
Daniel.Arick.Swamy
January 30, 2010 at 12:57 pm
Dear Sir,
My problem is HOT is going hot after few hour it will be short.Thanks for it i will follow this thip to repair the moniter. But please give some tip to solve this problem
Daniel Arick
admin
January 30, 2010 at 11:20 pm
HI Daniel,
You need to follow the steps above to solve the problem.
jestine
novell
February 7, 2010 at 10:49 pm
Hi Jestine,
I've been reading your blog and the support you are providing. It's fantastic.
I have a problem with my Philips 48" projection TV 48P977. There is no picture but everything else works. It can receive TV transmission. I can hear the whining sound that the flyback transformer makes but no picture. The filaments in the CRT tubes are working. I had removed the two HOTs, 2SD2539 and 2SC5521 separately and tested them with a DMM and both are ok. I don't have an I-V curve tracer or an oscilloscope. After soldering the HOTs back, there was no difference. There is still no picture.
I don't have the schematics or circuit diagram or any other specialised tools. Could you give some directions on how I can solve this problem? Thanks.
Regards,
Novell.
admin
February 8, 2010 at 6:03 am
HI Novell,
What is the G2 voltage that you get? In your Tv, the filament voltage comes from the flyback or from the main switch mode power supply?
Jestine
novell
February 10, 2010 at 7:00 am
Hi Jestine,
The filament voltage comes from the main switch mode power supply. Where and how do I measure the G2 voltage?
The two HOT transistors are clamped to the same large metal plate heat sink. I'm not sure whether this will help to diagnose the problem but I found out that this metal plate heat sink is cold when the power is switched on but the main FET and Deflection Processor (Vertical Deflector) heat sinks are warm.
Do you think there is a problem with the high voltage supply circuit? Or is the flyback kaput?
Thanks.
Regards,
Novell.
admin
February 10, 2010 at 9:27 am
HI Novell,
Then i guess the flyback is not energized. The flyback need B+ voltage from the SMPS and a horizontal drive signal for the HOT to turn on the flyback. Is there B+ voltage to the flyback? and signal to the HOT? The horizontal drive signal have to be test with a scope. If the flyback did not work then there will be no G2 voltage.
Jestine
m.satishkumar
February 11, 2010 at 11:47 am
Dear Sir,
My HCL HCM782M monitor setup automatically changing to incorrect setup. The automatic setup running for more than 5 mins. I am unable to view my desktop icons.Moreover, some option like vertical height and Pincushion set to 100 and I am not able to reduce it.
Thank you,
M.SATISHKUMAR
sahraoui
February 12, 2010 at 4:49 am
I find theses informations very useful for me as a beginner in tv and hardware computers repair ,thank you and good bless you
admin
February 12, 2010 at 6:15 am
Hi Sahraoui,
You are welcome!
Jestine
admin
February 12, 2010 at 6:18 am
HI Satish,
It could be the Eeprom data that had corrupted.
Jestine
Pradeep
February 13, 2010 at 6:39 am
Dear Sir,
I have a sony trinitron model KV-2199xf . the picture seems to have lost it's green color. The screen always looks very pinkish and blurry from the color missing. The light on the front flashes 5 times, stops for a few seconds, flashes 5 times, stops for a few seconds.
admin
February 13, 2010 at 9:05 am
HI Pradeep,
You may need to compare with the working red and the blue circuit in tern of voltage and signals. Sometimes a weak tube may cause such problem too. About the flashes, you may need to check for bad e-caps or even dry joints in the vertical or color section.
Jestine
Daniel.Arick.Swamy
February 17, 2010 at 1:44 am
Respected Jestine sir,
Before this also i will discuss this problem with you sir that in my moniter HOT is going warm after some two hour it going to distrub the picture. I"ll change the coupling capaciter also but no change comes. Please suggest some parmenent solution to solve this problem. please sir
admin
February 17, 2010 at 12:19 pm
HI Daniel,
Have you check all the suggestion above?
Jestine
Daniel.Arick.Swamy
February 19, 2010 at 1:35 am
Respected Sir,
I have check all component but problem is not solved
admin
February 19, 2010 at 11:30 am
HI Daniel,
If all check to be okay then i guess you may need to replace the flyback or the yoke coil to test it out.
Jestine
Doroteo
February 27, 2010 at 11:41 pm
Hello Jestine: I have a plasma tv Vizio Model HDTV20A, the two thermistor power supply burned. I can't find the parts , thermistor SCK086 ( Surge Current Killer ).
Regards
admin
February 28, 2010 at 1:23 am
Hi Doroteo,
Sorry, no exact part number from the internet. The best i can find is from this link:
http://parts.digikey.com/1/parts-kws/ametherm-thermistors
Jestine
frank kapoma bwalya
March 3, 2010 at 2:47 pm
Hi,for its not a comment but question.A 21"colo tv has a vetical black bar on both sides of the screen.what could be the possible causes and onather tv has same dotted lines on the screen,picture(picture not very clear) and sound are ok.keep sending the repair news there are helpfull.
admin
March 4, 2010 at 8:40 am
HI Frank,
I'm not sure about the second problem but for the first problem you may need to check the ESR filter cap at the SMPS because i've seen one before (only one bar at the side). Just make sure the output voltages are good.
Jestine
waleed dongol
March 8, 2010 at 2:52 am
Dear Jestine,
that is great,would you please help me how to understand how vertical circuit works.
thanks
admin
March 8, 2010 at 4:10 am
HI Waleed,
I guess you may need to get a book on Tv principles because vertical section is a big topic.
Jestine
Manish
March 14, 2010 at 7:00 am
Hello sir,
I m very much delighted after seeing the site like this........
i have a one problem regarding my monitor, my monitor just turned off on one fine working day. I quickly took my pc to the shop for repairing, after two days i bring it and same thing happen, it permanently turn off after 5 minutes. then i took my friend's monitor and again the same thing happen.
so now again i go to shop and he told me that something get shorted in ur monitor, so i checked my power supply board the what i see is it does nt show "earthing", so now you please tell me why my monitors fell both times is it due to power supply problem or my cpu(i.e. motherboard is having some problems)?, as i dnt thing due to earthing problem such thing can also happen.....
Manish
India
admin
March 16, 2010 at 1:41 am
HI Manish,
What type of Monitor LCD or CRT? Is the output voltages from the SMPS are good and stable?
Jestine
Manish
March 17, 2010 at 1:51 am
thanx for giving me time sir.....
mine monitor is CRT monitor and model is LG 15" 500G.
I hve nt checked the output volteges from smps, but every other component of cpu is working fine.
what kind of problem it may be i still cant get it.....
pls helm me to sort it out......
Manish
admin
March 17, 2010 at 9:18 am
Hi Manish,
May i know the output voltages reading of the SMPS. You may need to visit this link http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems
to isolate the problem.
Jestine
Manish
March 19, 2010 at 4:39 am
Hello Sir,
I will let u knw the status of smps voltages within 1-2 days............
Manish......
Bilal
May 15, 2010 at 3:48 am
Hi Justin
How r u ?i m glad to see this website that u help to solve the problem by your experience.Now come to my problem i have got a philips 14 inch colour TV modle no 14pt1582/57R.The problem is that when i on picture tube will not ON but its sound to be tik tik tik from the circuit i have check the HOT and got fine the collector voltage and the B+ volt is low to 97v which is not operating voltage of flyback.the voltage across filter capictor is also 97v.which is after the chopper transformer so help me that what should i check to and what i do plz rply thanks
admin
May 15, 2010 at 6:00 am
HI Bilal,
You need to check if there is horizontal drive pulse to the base of HOT.
Jestine
BILAL
May 17, 2010 at 4:09 am
HI
Jestine.
i dont have such kind of equipement so that i check the pulse at the base of transistor. i have digital multimeter through which i check the components as well as voltage.Can u tell me the simple way to check and solve the problem plz thanks
admin
May 17, 2010 at 8:07 pm
Hi Bilal,
You need the scope to check the right waveform to the base of HOT. There is no other way that i know of doing that. Digital meter can't detect such waveform.
Jestine
jeoffrey
July 11, 2010 at 6:24 am
hello ser jestine i have a problem of my monitor it doesnt turn on but the switch signal is color green i check a lot of electronic parts in my my CRT monitor but i cant see any shorted of bad parts i also check my HOT with ohmmeter and it fnctioned alot please help me.......... tnx