TV CRT problem

**Drew1369** · 06-28-2008, 05:46 PM

I have a monitor that is emiting a high pitched whine and several of the horizontal channels missing.

I think its the horizontal output transistor but I wanted to get some further feedback on some other things to check.

Any help would be great.

**Done_Fishin** · 06-29-2008, 11:37 AM

what do you mean by loss of channels .. do you mean that the screen is stretched vertically ?

unlikely to be the transistor but the problem might cause the transistor to blow

please explain better what the problem is .. if it was the transistor then most likely you would get no picture or High Voltage to the screen .. may not even power on .

**Drew1369** · 06-30-2008, 02:11 AM

Its not just 1 line thru... its multiple channels present and non... its random on the screen as well

**Done_Fishin** · 06-30-2008, 02:59 AM

I don't understand what you mean by channels unless you are saying that the tuner isn't working properly

the only relationship between tuner and horizontal transistor is that there is frequently a feedback voltage rail via the horizontal High Voltage flyback transformer

however you say horizontal channels which is confusing .

1. Is this Digital TV via cable or analogue reception from a Transmitter.
2. Do you get a picture from any or all TV stations
3. Is the picture normal in size and width and if not which is giving problems
4. I am assuming that you meant CRT and not LCD or Plasma by mistake.

in worst case try to take a photo ( hold camera sideways to take photo .. may give a better photo, sounds silly but try it with Digital Camera)

be quick though , don't want anything going bang whilst you're doing this .. sounds like you have a power supply problem

**Drew1369** · 06-30-2008, 04:23 PM

Sorry... throwback to the AF days...

The horizontal lines on the screen itself (called them channels in the Mil)

And yes... CRT not the others.

And its not a tuning problem

**Done_Fishin** · 06-30-2008, 10:33 PM

Hi Drew

if you are experiencing lack of linearity vertically and can see gaps in the scanning lines (channels) then the circuitry associated with vertical deflection is having problems.
It could be a bad diode, bad capacitor, bad Integrated circuit, even just bad solder joints around that area and including possible scan coil connections. Obviously one would need t get the patient to a doctor to see what exactly the problem is.
Hope this helps

codecreep · 08-21-2008, 04:07 PM

Hmmm
You have possibly thrown the TV out by now but would like to offer a few hints form my "TV fixing Days" about 150 years ago.

It could be something as simple as dirt, on the back of the CRT tube, causing the high voltage from the connection cup, to "creep" away.

Try this: Remove the back plastic panel, turn on the TV, and listen !!! at the back.
Can you hear a week "Hissing" sound comming from the CRT tube around the connection cup ????? If so it is dirt giving you troubles. Turn the power of, Disconnect the High voltage connection cup (use a pair of insulated playres, yuo have about 25.000 volt here), Dis-charge the CRT tube, (Ground an insulated screwdriver to the chassis with a wire and stick it into the hole in the CRT and LEAVE IT for about 1 minute)
Find your self some acetone and some paper towls and rinse of the area around trhe connection hole, it has to be totally clean, also rinse of the connection cup. Let it all dry for about an hour and re-assemble.

If this did not do the trick it is most likely the high voltage capacitor in the Horizontal output stage that is leaking internally (if so normally the problem gets less when the TV warms up) It is normally sitting somewere near the Transistor and is a few uF and about 400 volts. Get a new one from RadioShark and try out

Did this help ???? then I´m a Jack - D man

06-28-2008, 05:46 PM	#1 (permalink)
Drew1369 TSF Enthusiast Join Date: Jan 2007 Location: Seattle, WA, USA Posts: 2,310 OS: Vista Business	TV CRT problem I have a monitor that is emiting a high pitched whine and several of the horizontal channels missing. I think its the horizontal output transistor but I wanted to get some further feedback on some other things to check. Any help would be great. __________________ Marge: We wouldn't be in this trouble if you'd just paid the heating bill! Homer: I thought global warming would take care of it! Al Gore can't do anything right!

06-29-2008, 11:37 AM	#2 (permalink)
Done_Fishin Moderator Hardware Team Join Date: Oct 2006 Location: Brit living in Greece Posts: 5,040 OS: Win ME, Win XP Pro SP3, Ubuntu 7.04, Mepis 6.5 My System	Re: TV CRT problem what do you mean by loss of channels .. do you mean that the screen is stretched vertically ? unlikely to be the transistor but the problem might cause the transistor to blow please explain better what the problem is .. if it was the transistor then most likely you would get no picture or High Voltage to the screen .. may not even power on . __________________ D_F How to mark your thread as solved

06-30-2008, 02:11 AM	#3 (permalink)
Drew1369 TSF Enthusiast Join Date: Jan 2007 Location: Seattle, WA, USA Posts: 2,310 OS: Vista Business	Re: TV CRT problem Its not just 1 line thru... its multiple channels present and non... its random on the screen as well __________________ Marge: We wouldn't be in this trouble if you'd just paid the heating bill! Homer: I thought global warming would take care of it! Al Gore can't do anything right!

06-30-2008, 02:59 AM	#4 (permalink)
Done_Fishin Moderator Hardware Team Join Date: Oct 2006 Location: Brit living in Greece Posts: 5,040 OS: Win ME, Win XP Pro SP3, Ubuntu 7.04, Mepis 6.5 My System	Re: TV CRT problem I don't understand what you mean by channels unless you are saying that the tuner isn't working properly the only relationship between tuner and horizontal transistor is that there is frequently a feedback voltage rail via the horizontal High Voltage flyback transformer however you say horizontal channels which is confusing . 1. Is this Digital TV via cable or analogue reception from a Transmitter. 2. Do you get a picture from any or all TV stations 3. Is the picture normal in size and width and if not which is giving problems 4. I am assuming that you meant CRT and not LCD or Plasma by mistake. in worst case try to take a photo ( hold camera sideways to take photo .. may give a better photo, sounds silly but try it with Digital Camera) be quick though , don't want anything going bang whilst you're doing this .. sounds like you have a power supply problem __________________ D_F How to mark your thread as solved Last edited by Done_Fishin : 06-30-2008 at 03:01 AM.

06-30-2008, 04:23 PM	#5 (permalink)
Drew1369 TSF Enthusiast Join Date: Jan 2007 Location: Seattle, WA, USA Posts: 2,310 OS: Vista Business	Re: TV CRT problem Sorry... throwback to the AF days... The horizontal lines on the screen itself (called them channels in the Mil) And yes... CRT not the others. And its not a tuning problem __________________ Marge: We wouldn't be in this trouble if you'd just paid the heating bill! Homer: I thought global warming would take care of it! Al Gore can't do anything right!

06-30-2008, 10:33 PM	#6 (permalink)
Done_Fishin Moderator Hardware Team Join Date: Oct 2006 Location: Brit living in Greece Posts: 5,040 OS: Win ME, Win XP Pro SP3, Ubuntu 7.04, Mepis 6.5 My System	Re: TV CRT problem Hi Drew if you are experiencing lack of linearity vertically and can see gaps in the scanning lines (channels) then the circuitry associated with vertical deflection is having problems. It could be a bad diode, bad capacitor, bad Integrated circuit, even just bad solder joints around that area and including possible scan coil connections. Obviously one would need t get the patient to a doctor to see what exactly the problem is. Hope this helps __________________ D_F How to mark your thread as solved

08-21-2008, 04:07 PM	#7 (permalink)
codecreep Registered User Join Date: Aug 2008 Location: Demnark Posts: 4 OS: Vista	Re: TV CRT problem Hmmm You have possibly thrown the TV out by now but would like to offer a few hints form my "TV fixing Days" about 150 years ago. It could be something as simple as dirt, on the back of the CRT tube, causing the high voltage from the connection cup, to "creep" away. Try this: Remove the back plastic panel, turn on the TV, and listen !!! at the back. Can you hear a week "Hissing" sound comming from the CRT tube around the connection cup ????? If so it is dirt giving you troubles. Turn the power of, Disconnect the High voltage connection cup (use a pair of insulated playres, yuo have about 25.000 volt here), Dis-charge the CRT tube, (Ground an insulated screwdriver to the chassis with a wire and stick it into the hole in the CRT and LEAVE IT for about 1 minute) Find your self some acetone and some paper towls and rinse of the area around trhe connection hole, it has to be totally clean, also rinse of the connection cup. Let it all dry for about an hour and re-assemble. If this did not do the trick it is most likely the high voltage capacitor in the Horizontal output stage that is leaking internally (if so normally the problem gets less when the TV warms up) It is normally sitting somewere near the Transistor and is a few uF and about 400 volts. Get a new one from RadioShark and try out Did this help ???? then I´m a Jack - D man __________________ No Hazzle, Just Dazzle