Dead HP Pavilion v70 Monitor

Hello,

I'm quite new to electronics repair but I believe I do have a basic understanding of things. I've spent the better part of today troubleshooting a dead monitor. The monitor is an HP Pavilion v70, model number: P3209S, chassis: Tatung C7Es.

I've followed the FAQ a bit and tried to determine what I should do but I've gotten stuck. Over the past couple of weeks the horizontal deflection would cut out occasionally (wouldn't come back with a gentle whack) and would be fine after shutting it off to rest for a few minutes. Also, the picture's vertical deflection would squash down about an inch on top and bottom, but this could be fixed with a gentle tap, so I suspect it was just a loose connection.

A couple days ago it decided that it would not power up at all. There are no indications of power (no static, no clicks, no lights, etc.) Upon opening the case and plugging it in, if I listen closely I hear it clicking quietly like a clock (as in the FAQ.) I've tested the HOT and it appears to be shorted out and I don't measure voltage on it. I'm not sure I'm measuring it correctly, but I'm putting my black lead on a ground and the red lead on each leg of the HOT. I read 0V on each one.

Now, I've come to the conclusion that I should replace the HOT, but I'm not sure if this is the right course of action, nor am I sure if it's the full problem. I'd like to know if I've done everything correctly and what I should do next. I have access to a multimeter, 100MHz oscilloscope, and an ESR meter. If there is any information that I'm missing, I'll be happy to give more details if I'm able. I'd appreciate any help in repairing this monitor.

Thanks! James Bailey

Reply to
jbdude2000
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You have a long way to go, but you sort of have the right idea. It would be beyond the scope of emails to fix your monitor using emails.

You can heat the caps with a heat gun, and when warm, you can do the ESR testing. Many of the caps go high in ESR when they are warm. The ESR test is best done when both warm and cold.

Just keep in mind, that if you have a piece of equipment, and it is changing specs over a period of time, from when it was turned on, this means that there is something that has become thermo sensitive. If you give something a wack, and it starts to work, this is an indication that there is a cold solder connection, or something is making poor contact.

The horizontal output transistor (HOT), is best removed for testing. There are very low resistor values, and components of low resistance that are connected to the HOT, and thus, your ohm meter will not be practical to use to test it properly. Use the diode test option on your DVM to test semiconductors. If the HOT is a FET device, then it can get a bit tricky to do a simple test. Most of the time, when a HOT goes bad, it is usually shorted from the emitter to the collector. In the case of a FET, this would be from the source to the drain.

When troubleshooting any piece of equipment, start with the power supply first. In the case of a monitor, the next step is the high voltage (HV) area, and the scan amplifiers.

As for learning, TV equipment is about the worse to start with. The modern day TV sets and monitors, are very complex to start with. Even the sets of many years ago were not very simple.

Working on computer monitors is even worse than standard TV sets. The manufactures will not sell any service parts, and service manuals to any non contracted service people. In many of the cases with the new monitors, they are servicing them mostly at the modular level now. The cost of the labour, parts management, and the added training is too great in relation to changing a complete board while the unit is under warranty. After warranty, for the end user, a monitor can be too expensive to service.

Just take care for proper safety issues when working on display equipment. The power supply in a monitor or TV set can easily badly injure someone, or take their life. This type of work is a serious matter.

--

JANA
_____


 wrote in message 
news:1114304486.423269.81250@g14g2000cwa.googlegroups.com...
Hello,

I'm quite new to electronics repair but I believe I do have a basic
understanding of things.  I've spent the better part of today
troubleshooting a dead monitor.  The monitor is an HP Pavilion v70,
model number: P3209S, chassis: Tatung C7Es.

I've followed the FAQ a bit and tried to determine what I should do but
I've gotten stuck.  Over the past couple of weeks the horizontal
deflection would cut out occasionally (wouldn't come back with a gentle
whack) and would be fine after shutting it off to rest for a few
minutes.  Also, the picture's vertical deflection would squash down
about an inch on top and bottom, but this could be fixed with a gentle
tap, so I suspect it was just a loose connection.

A couple days ago it decided that it would not power up at all.  There
are no indications of power (no static, no clicks, no lights, etc.)
Upon opening the case and plugging it in, if I listen closely I hear it
clicking quietly like a clock (as in the FAQ.)  I've tested the HOT and
it appears to be shorted out and I don't measure voltage on it.  I'm
not sure I'm measuring it correctly, but I'm putting my black lead on a
ground and the red lead on each leg of the HOT.  I read 0V on each one.

Now, I've come to the conclusion that I should replace the HOT, but I'm
not sure if this is the right course of action, nor am I sure if it's
the full problem.  I'd like to know if I've done everything correctly
and what I should do next.  I have access to a multimeter, 100MHz
oscilloscope, and an ESR meter.  If there is any information that I'm
missing, I'll be happy to give more details if I'm able.  I'd
appreciate any help in repairing this monitor.

Thanks!
James Bailey
Reply to
JANA

I'm sure you are right about the HOT shorted. If it uses thermo grease, be surer to use a thin even amount (not the liquid y stuff when you first squeeze it out of tube). Next find the cold solder joint that took out the HOT. Since you were tapping or whacking it, look at the flyback for bad solder joints since it's heavy and more susceptible to movement, look for broken traces on board and check the electrolytic capacitors for bulges on top and an ESR meter for the others. Good Luck.

Reply to
Bill Degener

Okay, what I've gathered so far:

- Remove HOT and test properly, replace if necessary

- Heat caps and test ESR, replace bad caps

Is this generally all I need to do? Do I need to check for blown fusable resistors, etc.? I figure I need to do that considering I don't have voltage running to the HOT (if I'm measuring this correctly

- probe to ground and probe to leads of HOT).

Thanks again! James

Reply to
James Bailey

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