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Posted on Feb 03, 2010
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Tv has the power but no high voltage thus no raster

The problem is that the tv set sometimes works fine nomal from power on to changing channels and every other functions but sometimes not working at all like no high voltage thus no raster which is dark screen .
I read a little article about the panasonic tv has a problem with the power on /off , audio and video problems sometimes . I'd appriciate if anyone could give me a tip about this . Thank you .
my name is Kaz

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  • Posted on Feb 04, 2010
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This problem is actually related to most/all brands of lcd/plasma tvs/monitors. It is actually a bad batch of billions of capacitors. They were and still are, being used in any name, any size tvs etc.If you can get a fan near the back of the tv and turn it on medium at least, then you can prolong the life of the bad component, it helps them cool down (the problem is actually related/caused by overheating) I have a32" Poloroid lcd that I bought online broke, it shuts off every 3 minutes orso when I first turned it on. I noticed it seemedt o be a overheating problem as It happenend sooner and sooner the warmer the tv got..Any way here is my solution for you;The caps (capacitors) in the powerboard are going out. This is a very common problem in all class and price ranges of modern lcd and plasma tv's/ monitor's. I don't know if this problem has been like this for awhile or it just started, but either way, if the tv takes an abnormal amount of time to "warm" up then it most likely will go out all the way sometime in the (near) future. If you have a tiny bit of will and knowledge ypou can open the unit and get to the print board. Examine this for "popped" capacitors, they will have a buldging top instead of a flat one. Im gonna try to include a pic of them here, if i can get it this time, I've tried bfore lol. But you can google image a "popped" or "bad" capacitor and you would be able, with ease, to diagnose if you have any of these. Usually only one or two. Radioshack sells capacitors (couple anyway) for $1.59 each. MAKE SURE the replacement is of the SAME voltage or HIGHER, or you will be right back replacing those 2. Every capacitor has a negative pole marked with an (-) on the side of the capacitor(by one of the "legs", always puit the negative (-) "leg" of the new capacitor in the same hole in the printboard as where the previous negative (-) "leg" of the capacitor was ( a capacitor with the negative and positive "legs" put in backwards will result in the new piece "popping" as sson as you turn it on!!) make sure the "uf" rating (for example the most common popped capacitor is the 1000 uf) is the same as the one you are replacing. I needed 1000 uf, 105 c and 26v (volt) ratings for the 1 capacitor I needed to replace to fix my LG 19" lcd panel monitor I found by the trash that the light came on off, but it didn't come on. I replaced that capacitor with ; 1000uf, 85 c and 36 v (volts0...It works fine eventhough the volts and the temperature rating (36v and 85c) was not the same as the (26v(volt) and 105c ) capacitor I removed !! Further, I've replaced capacitors that had the celcius rating of 105 with the only ones Radioshack had, namely 85 c(celsius) they have been working great, but I'm not sure about any effect, nor have I heard or read (yet?) about that making an urgent difference. Many threads that I've read people have done the same, so we should be ok (my stuff has been running good for a while longer then most brand new ones!.............(all these ratings ; 'uf ' and 'c' etc are on the side of the capacitor you are replacing and on the side of the ones you are replacing them with)...For all this all you need is the cheapest solder gun u can find (I bought one for $7.99 at Radioshack), a camera (to take pictures as you go to remember how to reassemble the unit) and, once you have your materials, 20 minutes to replace 2 or 3 capacitors and you are good to go...Most monitors and tvs (lcd/plasma) I've seen you have to lay flat on the ground/bed/blanket etc, to work on (screen side down). Usually there are 2 or 3 screws (or a few more) to remove, then you will have to carefully (its comes off easily most times)insert a flat screwdriver inbetween the casing and gently pry it up as you go around the whole frame. Sometimes you have to remove the little washer arouind the cable input orso, just be gentle and you cant go wrong. Once insidet here will be a box with wires running to the sides etc...unplug, gently, these wires and open the box. Inside you will find 2 or 3 circuitboards, check them all for "popped" capacitors, replace, reassemble and plug it in....Have fun becoming an overnight tv mechanic lol! If this was helpful (or not)please rate, thank you!tv has the power but no high voltage thus no rast - 48f1e84.jpg

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Monitor no raster power has been ok
Hello,

The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.
Assuming there is no deflection and no High Voltage, you either have a low voltage power supply problem, bad start up circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.

Check for bad fuses.

(If you have High Voltage as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).

Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.
Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.
If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.
If there is voltage and no deflection (no high pitched whine and no HIGH VOLTAGE), you probably have a start up problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.
Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for start up problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself).

If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.

hope this helps......

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Aug 06, 2010 • SAMTRON 77V 17" CRT Monitor
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First, try a hard reset.
You must unplug the power cord (turning off the set or the strip will not do it) for a couple of hours, then try again.
This will sometimes correct the problem
When it blinks off: Does the raster go dark or just the picture and the raster remain?
If the raster goes dark when it blinks off it means there is a loss of high voltage to the picture tube. High voltage repair is expensive. It may be a failing flyback transformer that is functional inside the horizontal deflection circuits.
If the raster stays on and you just lose video (picture information) then it may be a simple intermittent IC chip in the video board area. It may require a technician to determine which IC and how to replace it or the parts associated with it, but probably not terribly expensive to repair.
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Hello,

The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.

Assuming there is no deflection and no HV, you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.

Check for bad fuses.

(If you have HV as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).

Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.

Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.

If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.

If there is voltage and no deflection (no high pitched whine and no HV), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.

Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself).

If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.
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Jun 02, 2010 • Toshiba MW27F51 27 in. TV/VCR/DVD Combo
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My hm67 50 inch sond but not pic heard loud pop and lost pic
Hello,

The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.

Assuming there is no deflection and no HV, you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.

Check for bad fuses.

(If you have HV as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).

Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.

Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.

If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.

If there is voltage and no deflection (no high pitched whine and no HV), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.

Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). See the section: Bypassing the Startup Circuit for details.

If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.
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Hello,

The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.

Assuming there is no deflection and no High Voltage , you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.

Check for bad fuses.

(If you have High Voltage as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).

Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.

Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.

If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.

If there is voltage and no deflection (no high pitched whine and no High Voltage), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osillator. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.

Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). See the section: Bypassing the Startup Circuit for details.

If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.
Hope this help
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May 30, 2010 • Televison & Video
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Hello,

The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.

Assuming there is no deflection and no HV, you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.

Check for bad fuses.

(If you have HV as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).

Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.

Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.

If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.

If there is voltage and no deflection (no high pitched whine and no HV), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available. Some Zeniths use a simple multivibrator for this - a couple of transistors. Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.

Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). See the section: Bypassing the Startup Circuit for details.

If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.
Good luck...
Read full answer
May 29, 2010 • Sony KV-32HS20 32" TV
0helpful
1answer

Jvc flat screen
Hello, The screen is blank with no raster at all. There are indications that the channel numbers are changing in the display. This indicates that some of the low voltages are present but these may be derived from the standby supply.
Assuming there is no deflection and no HV, you either have a low voltage power supply problem, bad startup circuit, or bad horizontal output transistor (HOT) or other bad parts in the horizontal deflection.
Check for bad fuses.
(If you have HV as indicated by static electricity on the front of the screen and you hear the high pitched whine of the horizontal deflection when it is turned on, then the following does not apply).
Use an ohmmeter to test the HOT for shorts. If it is bad, look for open fusable resistors or other fuses you did not catch.
Assuming it is good, measure the voltage on the collector-emitter of the HOT (this is safe if there is no deflection). You should see the B+ - probably between 100 and 150 V.
If there is no voltage, you have a low voltage power supply problem and/or you have not found all the bad/open parts.
If there is voltage and no deflection (no high pitched whine and no HV), you probably have a startup problem - all TVs need some kind of circuit to kick start the horizontal deflection until the auxiliary power outputs of the flyback are available.Others power the horizontal osc. IC from a special line-derived voltage. The multivibrator type are sometimes designed to fail if someone keeps turning the set on and off (like kids playing) since the power rating is inadequate.
Test the transistors if it is that type with an ohmmeter. If one is shorted, you have a problem. The usual way a TV service person would test for startup problems is to inject a signal to the base of the HOT of about 15.75 kHz. If the TV then starts and runs once this signal is removed, the diagnosis is confirmed. This is risky - you can blow things up if not careful (including yourself). This require a skilled personnel to handle this
If you hear the high pitched whine of the deflection and/or feel some static on the scree, confirm that the horizontal deflection and high voltage are working by adjusting the SCREEN control (probably on the flyback). If you can get a raster then your problem is probably in the video or chroma circuits, not the deflection or high voltage.
Read full answer
May 20, 2010 • JVC LT42E478 42 in. HDTV
1helpful
1answer

Bought a used ge46gw supposed to be fine brought hm 3days it went out, would work for 2-3 hrs at a time.....put in garage for a while moved it to another hse,now no pic at all sound is fine....where do I...
The reason there is no picture is (95%, certainty) the loss of the high voltage. The high voltage is what produces the energy for the raster lines upon which the video is modulated.

Therefore, the video and deflection circuits may be working just fine but you cannot see because there is no high voltage to the picture tube.

Now, it is possible, also that power to the picture tube filaments has been lost, or that the power supply to the biasing voltages is defective or that the picture tube sockets are corroded, but the overwhelming cause among TV sets is loss of high voltage.

Refurbishing the high voltage will probably cost $250 or from anywhere you go. Even if you do it yourself and buy the parts wholesale you will not save a tremendous amount. So, unless you are very handy and know how to troubleshoot, solder, repair and test, I think you are better off finding a good shop for the repair.

Replacing the high voltage regulator should fix the problem.

Good luck!
Read full answer
Mar 21, 2010 • Televison & Video
0helpful
1answer

IM A TV TECH. I HAVE A SONY LCD KP-60XBR800 I HAVE NO RASTER. POWER OK, MENU OK BUT NO RASTER ON TUNER, TUNER VOLTS OK,CAN YOU HELP ME PLEASE. THANKS my email [email protected]
check the high voltage with the screen control turned up high where there is no raster. suspect problem within the video circuit where there is no high voltage or defective picture tube.some time when the screen is black and the screen control advanced,you can see if the tv has video or vertical or horizontal problems on the screen.service the high voltage circuit if there is no raster or high voltage is seen.no raster can be caused by the no heater or filament in the CRT.---- a defective picture tube can cause many problems, such as, poor brightness ,missing colors,intermittent picture,poor focus,a single-colored raster,arching in the gun assembly,retrace lines in the picture,negative picture,chassis shutdown,noheater or filament lit and no raster to name a few.an open filament or heater can cause no picture or no raster symptom.a defective CRT can have an extremely bright screen.loose particles of the cathode element can lodge between the grids and cause an intermittent black and white picture. simply tap the ends of the CRT gun assembly and notice if the picture begins to flash off and on.---- with a leaky picture tube after turn on the raster dims and get extremely bright.a dim picture with no green in the raster can result from a bad green assembly. a heater-to-cathode short can cause a raster to change colour or a result in no raster at all.replace the picture tube if there is severe arching in the neck of CRT. excessive brightness with retrace lines and a vertical collapse to a thin line can be caused by a bad coil on the neck board of the picture tube.rejuvenate the picture tube when there is very bright green screen. check for the resistance change on the resistors of the CRT neck board for an excessively bright picture with retrace lines.excessive dust inside the CRT spark gaps within the picture tube socket can cause the very bright raster and the chassis shutdown.a defective video amp,luminance buffer,or reference transistor can cause a bright picture with retrace lines. -------- for getting any required parts to replace you can get it from www.radioshack.com or from www.partstore.com or from www.shopjimmy.com --------- thanks.please do rate the solution.thank you for using fixya.keep updated.
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Sep 06, 2009 • Televison & Video
0helpful
1answer

Sanyo TV Model# DS32224
This is usualy because there is either a high voltage regulation fault, or a main power supply regulation fault.

There are many things that can cause this. When the high voltage goes too far down, the raster will enlarge. High voltage regulation can be caused by faulty components in the feedback sensing, or in the high voltage multiplier, or in the flyback windings itself.

A quick way to sort of know if the high voltage is regulating is to wind the brightness and contrast from one extreme to another and observe the raster size. If the raster is changing size with the brightness on the screen, the regulation is not working well. In some of the low cost sets there will be about a 2 to 5% raster size shift in this case. The high end sets will have a near 0% shift in the raster size. A size change of about 2% is acceptable for most sets. If the CRT is weak, this test will not work well, because a weak CRT will not properly load.

If the main power supply is operating slightly over voltage, the raster size will increase. Usualy, the brightness will be a little on the high side when the supply is too high. Voltage regulation faults can be from warn components in the voltage regulator area, or in the feedback control.

This should be looked after by an experienced TV service tech. This type of fault can be involved.

Jerry G.


Read full answer
Nov 09, 2007 • Sanyo DS32224 TV
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