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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mathankumar
January 14, 2011 at 3:48 am
hello Sir,
Wish you Happy new year 2011
my problem is HCL 15" CRT Monitor display working but contrast and brightness automatically increase and decrease and always display the contrast name with percentage. please sir how to solve the problem please help me sir
admin
January 14, 2011 at 8:58 am
HI Mathan,
Check the eeprom and related circuit. The eeprom programs could have corrupted.
Jestine
waqas
January 20, 2011 at 8:57 am
plez give me ibm model 6331 image or datasheet or diagram so thanks advance
admin
January 20, 2011 at 10:53 am
HI Waqas,
Sorry i do not have such info
Jestine
Ray Sullivan
February 13, 2011 at 9:54 pm
I have a normally functioning Sony HDTV CRT KD30XS955 purchased in 2005. Est. time of use for the past 5 1/2 yrs is
admin
February 14, 2011 at 3:57 am
HI Ray,
May i know what is your question?
Jestine
mathankumar
February 19, 2011 at 2:09 am
my problem is 15″ HP TFT monitor No picture, power led Flowing and white display comes.please sir give more tips for to solve
admin
February 19, 2011 at 11:09 pm
HI Mathankumar,
If there are good voltages at the lcd controller board in the lcd panel then suspect lcd panel have problem.
Jestine
Harry
March 8, 2011 at 6:26 am
Hi Jestine, My PC monitor horizontal shrinking to the middle about 20 pixels wide only, where should I locate this trouble?
admin
March 8, 2011 at 10:53 pm
Hi Harry,
Yours is a crt or lcd monitor? If it is a crt monitor then you need to check on the modulation diode and pincushion transistor for short circuit. Check also for B+ voltage because if it is not high enough the display will shrink.
Jestine
Harry
March 11, 2011 at 1:29 am
Hi Jestine , my monitor is crt, there's one resistor(3watt) that goes to a transistor(TIP 31A) it was burning.
What cause it to burned? How can I replace it with a correct value since the color of the rings is not visible anymore?
There's a coil that going extremely hot too.
How can I locate the problem?
admin
March 11, 2011 at 8:53 pm
HI Harry,
The burnt resistor was due to something shorted especially the semiconductor TIP31A. Check also the coil surrounding to see if there is any component shorted. If it is totally burnt into crisp i suggest that you locate the schematic or compare with the same model of equipment.
Jestine
Harry
March 11, 2011 at 11:24 pm
Hi Jestine, what's the function of PTCR at the power supply section?, cause it run very hot too.
I still can't find the B+ pin of the flyback.
admin
March 12, 2011 at 2:10 am
HI Harry,
The PTC is degausing purposes and it is normal to be hot. The B+ pin, you have to trace from the power supply output and it will pass through B+ coil and a diode before the voltage reaching to one of the pin in flyback. That pin is the B+ pin.
Jestine
Harry
March 12, 2011 at 3:56 am
Thanks Jestine, the power supply section have a High Pot transformer, which one is the output for B+ ?
admin
March 12, 2011 at 11:00 pm
HI Harry,
You should trace after the power supply and not in the power supply. The hipot transformer is actually the transformer of the power supply. You should be looking at a coil (it can be round and sometimes like a small transformer). and nearby this coil there will be a fet.
Jestine
Harry
March 12, 2011 at 11:03 pm
Hi Jestine, I tried to test the flyback with a digital multimeter, when only one of the probe touch the HOT's collector there's a small blue spark coming from it, and the multimeter read beyond its range (>1000v). Is that normal?
admin
March 13, 2011 at 4:13 am
HI Harry,
You can't test the point that way because it can sometimes kill the meter. The peak to peak voltage is more than a thousand volt. If you have the high voltage probe then it will be good for you to test the anode voltage to see if the flyback is working or not. Please visit the link below for more info:
http://www.electronicrepairguide.com/testing-flyback-transformer.html
Jestine
abdulla
March 14, 2011 at 1:06 am
sir,i have lg studioworks 500g crt monitor ,prolem width is too high i cannot adjust pls help me
admin
March 14, 2011 at 5:33 am
HI Abdulla,
You need to check on the modulation diode and make sure no short circuit in the pincushion transistor.
Jestine
Daud
March 20, 2011 at 6:34 am
Sir,these are very useful tips for an average technician like me. thanks
GAURAV
March 20, 2011 at 7:34 am
my moniter display is band at 60 degree angle
admin
March 20, 2011 at 10:55 am
HI Gaurav,
Do you have a photo? Have you try adjust the crt yoke coil?
Jestine
jerin j mathew
March 22, 2011 at 2:46 am
my LG 17" CRT monitor display shifted to right and can see a 1" black bar on the left and there are flickering lines..... is this due to complaint in hot
admin
March 22, 2011 at 9:10 am
HI Jerin,
If the HOT did not get hot then most likely it is not the HOT problem. Try replace the h/v oscillator ic and retest.
Jestine
jerin j mathew
March 26, 2011 at 11:51 am
Dear Jestine,
my LG 17″ CRT monitor display shifted to right and can see a 1″ black bar on the left and there are flickering lines…..
Thanks for your reply. The HOT did not get hot.h/v oscillator IC checked and found correct.I checked the board and corrected some dry and loose soldering in horizontal driver ckt section, changed two 470uf 16v capacitor which are bulged. When the power supply is switched on again fuse blown and found the FET in power supply ckt shorted.What's the problem with?
Vijay
March 27, 2011 at 12:52 am
Hi Jestine,
Is it possible the HDY coil get shorted?
Can I test HDY coil with multimeter?
jhay
March 28, 2011 at 3:37 am
hi there mr yong,im jhay from philippines,im pleased to have you as my mentor,i want to become a good technician someday
-jhay
admin
March 28, 2011 at 5:43 am
HI Vijay,
HDY coil can go shorted and it can't be tested with multimeter. You need a blue ring tester to test it.
Jestine
admin
March 28, 2011 at 5:48 am
HI Jhay,
Try visit this link below as i found it to be very good:
http://www.repairfaq.org/REPAIR/
Jestine
admin
March 28, 2011 at 5:53 am
Hi Jerin,
I suggest that you isolate the problem using the link below first:
http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems
You may need to check all the components again in the power section and directly replace the power ic and retest.
Jestine
Vijay
March 29, 2011 at 1:52 am
Hi Jestine,
Thanks for your answer, can I build my own tester like this one I found on website: http://members.ozemail.com.au/~bobpar/fbt.htm.
Is this tester the same as the blue ring tester?
admin
March 29, 2011 at 8:41 am
Hi Vijay,
The link is not working.
Jestine
Vijay
March 29, 2011 at 1:54 pm
Hi Jestine, here's another link: http://www.flippers.com/fbt-main.html
raaj
April 9, 2011 at 7:18 am
thanks a lot sir . sir your tips are very valueable for me in my colour tv repairing field thanks again
Wakheel
April 30, 2011 at 8:14 am
Thank you for the info that you give to me . But out of that info there is some things that not clear to me. They are : how to measures the frequency on HOT . What is meaning of B+ on tv
admin
April 30, 2011 at 9:33 pm
HI Wakheel,
By measuring the base of the HOT using a frequency meter or scope. B+ i the supply voltage to the flyback transfromer primary winding.
Jestine
jefu
May 6, 2011 at 10:47 pm
hi! jestine good day! if the tv is blue picture,normal sound normal images but all is blue pictre..the problem is the blue color drive? i'm correct?
admin
May 7, 2011 at 10:10 pm
HI Jefu,
Yes you are right and you can compare the red/green signals/voltages for troubleshooting purposes
Jestine
teklay
May 13, 2011 at 10:54 am
dear Jestine,thanks for your helpful suggestions.it really helps many people like me.
Amir Mukhtar
May 14, 2011 at 1:41 am
Sir, Horizontal output transistor need to be replaced same with original one.
But in pakistan there is no guarantee of original transistor. so therefore, guide us how to check and confirm before replace the transistor at shop during buy wheather HOT is original or not.
plz guide.
thanks you
Amir mukhtar
admin
May 14, 2011 at 8:18 pm
HI Amir,
The replacement number should have the same or higher spec than the original one. Check for the datasheet and make sure the replacement part have similar hfe and storage time.
or you can replace and turn it on for a while. if the HOT gets hot within a second or a minute then it can't be used. If it is running warm then make sure you test on highest resolution. If it still running slightly warm then the HOT can be used.
Jestine
fahim
May 20, 2011 at 11:12 pm
I agree this information
mathan
June 25, 2011 at 12:35 am
hello sir,
my problem is HCL LCD 14″ Monitor No picture, power led blinking. please sir give me some information on how to identify the faulty components
mathan
admin
June 25, 2011 at 8:05 am
HI Mathan,
Make sure the output voltages from the power supply are good and stable. If it is stable then suspect problem in the mainboard.If it is not stable then check the power side and the secondary filter capacitor.
Jestine
Sandeep
June 30, 2011 at 4:40 am
i have a HCL 17″CRT monitor. It have problem from 3 months that it’s blink the setting of monitor. It is work the setting for adjusting but when we work or seen the video then the problem accurs.
regard
sandeep
admin
June 30, 2011 at 7:37 am
HI Sandeep,
Could you elaborate because i don't understand your meaning?
Jestine
mathan
July 5, 2011 at 6:52 am
hi
my problem is COMPAQ 15″ Monitor was not working smps section ok. when cpu is switched on the monitor green LED Flowing but not display the screen only black screen display. please give some tip to solve this problem
admin
July 5, 2011 at 9:16 pm
Hi Mathan,
Have you check the B+ voltage. Make sure there is a pulse at the base of horizontal output transistor.
Jestine
Tipu
August 24, 2011 at 11:21 pm
Hi ! Mr. Jestine
My China kit 21 inch color TV flyback transformer +180V output winding(also the heater winding) pin 7 and pin 8 is shorted as measured with my Dick Smith flyback tester
No high voltage to picture tube got.
the hor output transistor V432 1803D is OK
The set is dead
This set uses Toshiba TMPA8873 64 pin IC and LA78040(N451) vert IC and i have the circuit diagram
Sir, can you please advise how to repair this problem?
thanks !
Tipu