Question about Mitsubishi WS-55511 55" Rear Projection Television

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No reading on Horizontal Output Transistor...power supply?

After following your guidance, I found the DM Power Supply still had a green light lit up, nothing seemed blown, blackened or swollen in the DM panel. The Horizontal Output Transistor did not show any activity on the meter. Is this the part to replace, or is it the Power Supply itself, and who should I buy it from?
-Thank You

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  • getsarge Aug 25, 2008

    I am unable to locate your original posting, do you mind reiterating what the next step is?

    Thank you,

    EC


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  • 4,234 Answers

I have provided the next step in the original posting. I'd rather kep the discussion there to maintain the context of the entire problem.

Thanks,
Dan

Posted on Aug 25, 2008

  • ABRsvcs Aug 25, 2008

    The noise you are hearing is from oone or more parts in the switch-mode power supply that are oscillating. If this is all you get when attempting to startup the set, the problem is in the power supply itself or it is a dead short further along. The power supply it trying to work and failing. The first thing to check is the horizontal output transistor. This is a 3-legged part attached to a heatsink and shouldbe close to the flyback transformer (part with large red wire coming out of the top). Check this using an ohmmeter. You should read resistance when measuring between either outer leg and the center. If any of those read zero(0) in both directions, the part is bad and should be replaced.

    Try that first. If that fails to resolve the problem, update this and we'll continue on to the next step.

    Dan


    Comment by Abrsvcs, posted on Aug 25, 2008
    Perhaps you mis-understood. Since the set is not powered up, there will be no voltage at the horizontal output transistor. You need to make the measurements I outlined above with the set unplugged.

    Second: If the power supply does not kick in at all and the transistor measures OK, then we need to look at the power supply area itself. Close to the area where the AC cord connects to the board you should see some capacitors that have a value in the 2.2-4.7ufd range with a working voltage of 200V or more. Try replacing those caps and report your results here.

    Dan

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Related Questions:

Tip

How to test Flyback Transformer Without taking it off the Boarda) Basically it...





How to test Flyback Transformer Without taking it off the Board


a) Basically it has to be acted upon by a supply voltage of at least 95V

to work.



sample picture:


7_31_2012_2_32_48_pm.jpg

b) Of course, assuming the horizontal deflection oscillator works, same

with the horizontal drive and horizontal output transistor



sample of H out transistor

7_31_2012_2_38_05_pm.jpg


It would generate output voltages on the secondary terminals

and 200V line will be active sending voltages to the

Video Drive circuits. Of course high voltage will be generated

ranging to at least 30 KV and there will be voltages on the G2 of the CRT.


c) The easiest test point to look when it is oscillating, is the CRT heater

voltage, the heater lit when flyback is good ( mostly at night times when it

is dark ) and you can hear sounds, too ( if speaker is connected).






7_31_2012_2_42_22_pm.jpg


• Heater : marked with letter H and H1

• Green Arrow for the G2 voltage


d) Having a B+ voltage reading of 75 V or lesser ( primary pins )

indicates a bad or partially shorted flyback, assuming your

horizontal output transistor and power supply are good & OK.





7_31_2012_2_47_50_pm.jpg





• These only applies to CRT type TV's.

on Jul 31, 2012 | Philips Televison & Video

Tip

A) basically it has to be acted upon by a supply voltage of at least 95V to...


a) basically it has to be acted upon by a supply voltage of at least 95V

to work.

sample picture

f3f741f.jpg







b) of course, assuming the horizontal deflection oscillator works, same

with the horizontal drive and horizontal output transistor

58689de.jpg






it would generate output voltages on the secondary terminals

and 200V line will be active sending voltages to the

Video Drive circuits. Of course high voltage will be generated

ranging to at least 30 KV and there will be voltages on the G2 of the tube.


c) the easiest test point to look when it is oscillating, is the CRT heater

voltage, the heater lit when flyback is good ( mostly at night times when it

is dark ) and you can hear sounds, too.

here is a sample image

ab6c901.jpg



marked with letter H and H1

Green Arrow for the G2 voltage


d) having a B+ voltage reading of 75 V or lesser ( primary pins )

indicates a bad or partially shorted flyback, assuming your

horizontal output transistor and power supply are good & OK.

sample of H out

b3363d6.jpg


These only applies to CRT type TV's.

on Dec 24, 2009 | Music

2 Answers

Power light goes on (green ) for about 3 seconds then shuts off


the tv have a fault in the power supply circuit or horizontal circuit check the regulator transistor or ic in your power supply and other components there.check the horizontal output transistor in the horizontal circuit and other components around replace what ever component you find faulty and components associated with the faulty component.good luck.

Sep 25, 2011 | LG 42LC2D 42 in. LCD HDTV

1 Answer

SONY KP-61V90 tv will not power on, red light in front,


Its 2 times blink error code that shows +B volt supply (+135 volts) is shorted, most probably horizontal output transistor is shorted, replace it.
If you are good in soldering parts in circuit board then take out horizontal transistor, check it, found shorted then replace it with same number.

Horizontal output Transistor Q502 number is 2SD2578 and available in Part Store for $10
Let me know for further query, if any.
Thanks.

Nov 18, 2009 | Sony Televison & Video

Tip

How to test flyback without taking it out of the board


a) basically it has to be acted upon by a supply voltage of at least 95V

to work.

b) of course, assuming the horizontal deflection oscillator works, same

with the horizontal drive it should generate output voltages on the

secondary terminals

c) the easiest test point to look when it is oscillating is the CRT heater

voltage, the heater lit when flyback is good.

d) having a voltage reading of 75 V or lesser on its primary pins

indicates a bad or partially shorted flyback, assuming your

horizontal output transistor and power supply are good & OK.


These only applies to CRT type TV's.

on Dec 03, 2009 | Televison & Video

2 Answers

No picture


I disagree with given info, this tv has no horizontal output transistor because it is dlp tv.
3 red light blink means lamp cover is not placed back properly after lamp replacement/ lamp checking. Make sure lamp cover is fixed back in its place securely and tight.


Jul 16, 2009 | Sony Grand WEGA KF42WE610 42" Rear...

1 Answer

Start up problem.


I suggest you look at the Horizontal output transistor, when it goes short the supply is in protection mode, it is pointless reading voltages at this stage, check the transistor located close to the Horizontal output (Flyback) transformer and normally mounted on a large heatsink. Check the caps in the primary power supply stage....hope that helps..Phil

May 19, 2009 | Televison & Video

1 Answer

Will not turn on.


  • proceed as given after your power supply is ok (your statement)
  • isolate power supply from h/output stage.
  • check diodes & capacitors connected with flyback transformer.
  • check for print short.
  • ckeck h/output transistor.
  • connect supply to h/output stage.
  • put on the set.
  • hope this will help.
  • good luck

still there is a drop in voltage then your fly back transformer faulty.

 

Oct 12, 2007 | RCA F32450 32" TV

1 Answer

No power even standby LED..


This is like a car running without a driver,the horizonatl output transistor has the voltage it needs but it does not have horizontal drive signal applied to the base of the horizonatl driver transistor,the driver transistor should have a signal coming from the signal processor where the signal is generated just to get give it to the driver this driver then it gives it to the output to energize the flyback and light up the picture tube and generate a few other supplies,158 volts are there because the output is not turn on,try measuring voltage somewere else in the set and not at the collector of the output,there is a b+supply that goes to the signal processor(8 to 12 volts),check to see if you have this voltage,I couldn't tell you the pins in the siganl processor IC without squematic,It seems you know your way around tv service but be careful when checking voltages.Let Us know if you need more information.

Oct 10, 2006 | Samsung TXJ2067 20" TV

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