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Question about SAMTRON 55V 15" CRT Monitor

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Low brightness

I havelg cb775cna maonitor,its very low brightness. i cheked the voltages of filament and screen these are normal.i could't find any components abbout brightness section ..anybody help me?

Posted by Anonymous on


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He is talking about the screw on the flyback. It is on the high voltage part of the circuity. I resell monitors and computers and I have to take off the back to get to this. I would not recommend it to a novice. This will light up your life. When you turn it up too much you get those scan lines across the screens. To find the fly back look for the heavy plastic thick thing on the circuit board to the back away from the picture tube. I had one of these on a samsung tv that looked like an arc welder. It is best to leave it unplugged for 48 hours for the electricity to discharge.

Posted on May 18, 2007


Samuel Konger

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I did not understand the term 'normal', but you can try increasing the screen from the FBT Potentiometer knob.

Posted on May 04, 2007


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My TV brightness is very low? It's a telefunken.

Maybe your light blub inside TV is dimmed down due to long time usage. This can be replaced. Also check light settings in the option menu.

How to check filament in tv

If it has a picture tube first look with set on, three tiny filaments will be lit if good, not real bright as 6.3 volts ac voltage across two pins on the actual tube.

If you can see them lit they are ok---most sets mark them on the board at the end of the neck for the picture tube with H for heater.

Very carefully as high voltages on the board measure for 6.3 volts AC across those pins. If for example its 3 volts that is too low and the voltage from those pins can be physically traced back to the High voltage transformer creates it off two pins.

less than 12 connections between source and the board on the tube, if missing voltage at the tube follow it back--a single cracked or bad solder connection can cause this.

The displayu screen does not light up brightly ==it is very faint, is this caused by low voltage to the drivers or something else and can it be repaired

If the fault is only with the DISPLAY then there is no need to be concerned as this is due to low filament voltage or grid volage or a faulty display driver IC.
So check with the filament voltage which is about less than 3 Volt AC. Also check for the display grid negative to the IC and display so as to confirm the case.
If there is no other issue you might as well not tamper if you are not equipped as a false move can cause heavy damage.

My microwave will not heat model #mw8119sb

Hello there and welcome to fixya
Testing the magnetron WARNING: First, with power disconnected, discharge the high voltage capacitor. See the section Safe discharging of the high voltage capacitor.
  • A magnetron with an open filament will result in no heat but no other symptoms. The bad connection may be internal (in which case the magnetron will need to be replaced) or external at the filament terminals (which may be repairable).
  • A magnetron with with a short between the filament/cathode and anode will likely result in a loud hum from the HV transformer and/or magnetron when the cook cycle is initiated but the main fuse will probably not blow. However, note that the actual wattage drawn from the power line will probably be much lower than under normal conditions. Although there will be a high current flowing in the HV transformer secondary through the HV capacitor (likely causing a loud hum or buzz), the real power consumed will be reduced since the current and voltage will be out of phase (due to the series capacitor) and the power factor will be low. A reading on an AC line wattmeter of 300 W compared to the normal 1,200 to 1,500 W would be reasonable.
  • A magnetron with other faults may result in a variety of symptoms including erratic or low output power or intermittent operation. See the section: Comprehensive list of magnetron failure modes.
There is no totally definitive way to determine if a magnetron is good without actually powering it under operating conditions but the following tests will catch most problems:

  • Magnetron filament. The resistance should be infinite from the filament connections to the case and a fraction of an ohm between the filament terminals with the wiring disconnected from the magnetron. While measuring resistance from filament chassis, gently tap the magnetron to determine if there is an intermittent short. However, such problems may only show up once the filament heats up and parts expand.
    It may be possible to determine if the magnetron filament is actually working by connecting just the filament connections to a low voltage high current supply on a Variac (e.g., a microwave oven transformer but just the filament connections). Most ceramic insulators are translucent and should show a glow with a working filament. The one at the antenna may be visible if the magnetron is removed from the oven or with a dental mirror looking into the waveguide. WARNING: Make sure you ONLY have the filament connected!
    I tried powering the filaments of a few magnetrons. On those that had white or pink ceramic insulators between the antenna cap and body of the magnetron, the glow was very bright. Even on one with a dark red insulator, the glow could be seen with the lights out.

  • Evidence of arcing (visible blackening around ventilation holes in base or burnt odor) usually indicates a bad magnetron.
  • Melting or other damage to the antenna cover ('bull-nose' or 'bullet') may be the result of arcing due to problems in the oven cavity or waveguide (perhaps operating with nothing in the oven) or a defective magnetron. (This part is only visible with the magnetron removed from the oven). If a problem elsewhere has been corrected, the damaged antenna cover can be pulled off and replaced from a magnetron that died of other causes - try your local appliance repair shop. (The shape doesn't matter as long as it fits tightly - there are several diameters, however.) Your magnetron may still be good.
    Note: Since the antenna is attached directly to one of the vanes which is part of the anode assembly, it will test as a dead short to the case on your multimeter using DC and is normal. At 2.45 GHz, this won't be the case! :)

Picture is dark, so you have to turn up the black level, contrast, etc. is that the picture tube or have you heard of this problem before, maybe something inexpensive and easy to fix

the picture tube is already weak. if you could only have a reduvinator it will be good again, it is a instrument used to reduvinate the picture tube.

Have headlight problem 2002 chevy malibu v-6 on the dim side have electria current on both wires to the blub bright beams function normal

if you have power to both headlight plugs for each low and high beam filaments and the ground is good as you say the high beams function normally then you either have bad low beam bulb filaments,poor or dirty connection or you have a daytime running headlight relay on the car and that is the problem with the low beam lights.yes the high beams will work but not low beams if it is the relay.

When I turn on my TV I have sound but no picture

ths is a coman problum in tv it is a two type of problum solonution
[1]check filament voltage on crt base and check filament is on if not then Resolder filament ragistance or replace with new
IF filament is OK then ......
[2] check screen voltage hight more then normal and see the screen H line on the screen then problum is vartical section then check or replace capaceter /registance /vartical IC


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 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 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 or from or from --------- thanks.please do rate the solution.thank you for using fixya.keep updated.

Hatachi 53FDX01B

The screen drive or filament voltage is low
increase the the screen drive first.
mounted on the flyback transformer.


Getting More Brightness/Contrast ?

problem with my monitor Viewsonic E70....Memory recall keep flashing......any help out there.....
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