Sceptre Shlepter

[mmmbuh]

I guess I'm having the same problem plaguing everyone who has ever purchased one of these has experienced...I need to replace some or all of the caps in this thing. The problem is that I don't want to beat the hell out of the case opening it up. I assume there is a trick to it? Inserting tools in the right place maybe? Thanks for any advice. It's a x22wg by the way.

[PlainBill]

Re: Sceptre Shlepter

I guess I'm having the same problem plaguing everyone who has ever purchased one of these has experienced...I need to replace some or all of the caps in this thing. The problem is that I don't want to beat the hell out of the case opening it up. I assume there is a trick to it? Inserting tools in the right place maybe? Thanks for any advice. It's a x22wg by the way.

No special tricks. Remove the base and all visible screws from the back. Start at the bottom of the case and insert a thin tool (putty knife, sharpened guitar pick, expansion slot cover) into the crack and separate the front of the case from the back. The two halves have lips that overlap overlap; the lip on the front overlaps the lip on the back. Slide the tool along, releasing the catches as you go. Do the same on the sides, then the top.

PlainBill

[mmmbuh]

Re: Sceptre Shlepter

Thanks

[mmmbuh]

Re: Sceptre Shlepter

ok, got it open...
The problem I have is that after turning the monitor on, it only stays on for about 1 second, then goes blank. In multiple online forums, I've read this is typically the capacitors. Now that I can see them, there is no visible damage to the caps at all that I can see. The ones that I read that are the culprits are right by the power plug, and there are 4 of them, a 35V 470uf, and three 10v 1000uF. None have any bulges, top or bottom, no leakage, and none are leaning like they would if the plug was blown out. So is it possible one or more are still bad, even thought there is no physical evidence of it?
There are a few other misc caps on the board, and none of them show any damage either...
Mike

[PlainBill]

Re: Sceptre Shlepter

ok, got it open...
The problem I have is that after turning the monitor on, it only stays on for about 1 second, then goes blank. In multiple online forums, I've read this is typically the capacitors. Now that I can see them, there is no visible damage to the caps at all that I can see. The ones that I read that are the culprits are right by the power plug, and there are 4 of them, a 35V 470uf, and three 10v 1000uF. None have any bulges, top or bottom, no leakage, and none are leaning like they would if the plug was blown out. So is it possible one or more are still bad, even thought there is no physical evidence of it?
There are a few other misc caps on the board, and none of them show any damage either...
Mike

"A picture is worth a thousand words". Good pictures of both boards will help us.

A couple of tests will help diagnose the problem. Hook it up to a working computer. Does it display an image in the second it is on? Does the power led go off, then on again, or does it stay on? If you cycle the power button off, then on, does the display come back for a second?

Now about you - what experience do you have? What test equipment do you have? Do you know how to solder?

PlainBill

[mmmbuh]

Re: Sceptre Shlepter

Now that I see the camera images, it looks like the smaller cap to the right of the other 4 in pic #38 might be a bit puffed up. Doesn't look like the photos I've seen of blown caps though...but i'm no expert. When it is turned on, the display looks just fine, it just only stays on for a second or less. Turning it off then on again does the same thing every time, an image of the desktop for about 1 second, then blank screen. I don't remember if the power led stays constant, or blinks, or what else...it is disassembled right now, is the led a critical sign to tell the problem (do i have to connect everything back up to tell you?)
I have lots of soldering and general electronic experience, I build pc systems, etc...this is just the first time working on the basic components. I have good working knowledge of the concepts of all this stuff, but don't know if I have the right equipment to do the tests. Probably the only thing I might have that may be helpful is the digital voltmeter I use when working on my car.
If it is the caps, I don't think I'll have any problem replacing them, I'm just hoping to find out if that's what it is before I order the caps and take the time to do the work.

thanks for your help...

[Toasty]

Re: Sceptre Shlepter

KZH fails? Very odd. Looks like an 'o6 date code too. Even odder.

I think the problem may be bad tubes or cold solder joints on the HV transformer. Could also be connections at the HV leads to the tube ends. Pic of bacside, concentrate on HV transformer pins and reflow with fresh rosin core solder. Check other connections across board.

**DO NOT OPERATE UNIT WITHOUT TUBES CONNECTED**

Unit goes to shutdown after -good- display? Happen suddenly or 'weirdness' beforehand?

No pinkish hue to backlight?

Do you have a case-mod CCFL unit you can use to check the backlights?

Toast

[PlainBill]

Re: Sceptre Shlepter

Now that I see the camera images, it looks like the smaller cap to the right of the other 4 in pic #38 might be a bit puffed up. Doesn't look like the photos I've seen of blown caps though...but i'm no expert. When it is turned on, the display looks just fine, it just only stays on for a second or less. Turning it off then on again does the same thing every time, an image of the desktop for about 1 second, then blank screen. I don't remember if the power led stays constant, or blinks, or what else...it is disassembled right now, is the led a critical sign to tell the problem (do i have to connect everything back up to tell you?)
I have lots of soldering and general electronic experience, I build pc systems, etc...this is just the first time working on the basic components. I have good working knowledge of the concepts of all this stuff, but don't know if I have the right equipment to do the tests. Probably the only thing I might have that may be helpful is the digital voltmeter I use when working on my car.
If it is the caps, I don't think I'll have any problem replacing them, I'm just hoping to find out if that's what it is before I order the caps and take the time to do the work.

thanks for your help...

First, the criticism - attach pictures using the 'Manage Attachments button below the reply box, not the 'Insert Image' icon above it.

Now the good news - good pictures. I agree, the caps look fine. That isn't an absolute proof. The poorest Chinese manufacturer knows how to build capacitors that will fail without bulging. Given the symptoms and the appearance of the caps, I'm going to assume you have the 'two seconds to black' problem.

Lecture mode first: Here's the normal way an LCD monitor works. It powers up. The Controller on the logic board runs a self test, then tells the inverter controller to turn on. The inverter controller turns on the CCFL backlights at full brightness. After a second or two it starts monitoring the voltage across the backlights and the current through them. If either is out of spec (too high or too low), it shuts all backlights down. It has no way of informing the controller on the logic board that it has done this. At the same time the controller on the logic board is checking for video signals, processes them, and displays them. If it can't find video signals it will eventually go into standby mode, telling the backlight controller to turn the CCFLs off, and it starts flashing the power led (or switches it off, turns it orange, etc).

NOW, here's where things get difficult. If the power LED stays green after the display goes dark, it could be bad CCFLs, or an inverter problem. Possible CCFL problems include 'worn out' or broken CCFLs, arcing to the panel frame, or bad solder joints. Possible inverter problems include bad caps, bad transistors, bad transformer, bad monitoring circuit, bad soldering joints, etc, etc. Measuring the transformer output is not safe - we're talking about 650-1000 VAC at 10 ma and 100 khz. Enough voltage and current to give you a bad day, but unlikely to kill you. Also enough voltage to fry many DMMs.

There are two ways to check these - indirectly and directly. Checking indirectly involves using a 'case mod light kit'. Use the kit inverter to power the monitor CCFLs. If one doesn't light, you've found the problem. Use the kit CCFLs to test the monitor inverter outputs. If one (or more) outputs will not light a CCFL, we know where to start.

Testing directly is a little more tricky. It MAY be possible to check the voltage on the return line from the CCFL. It depends on the specs on your DMM and how brave you are. If your DMM is rated to measure AC signals at over 100 khz, you can use it.

Examine the wires from the inverter to the CCFLs. Notice that one is larger in diameter. That is the drive line to the CCFL. The smaller one is the return line, and is at a safe voltage. Let me know if you want to carry on with testing it directly.

PlainBill

[mmmbuh]

Re: Sceptre Shlepter

Turn on the monitor, it shows normal desktop image, then image just shuts off like I had just hit the power button. No weirdness, no pink hue.
Have no spare CCFL. Will check connections and post pic of back later tonight.
Why is the date code odd?
Mike

[370forlife]

Re: Sceptre Shlepter

Why is the date code odd?

They're not particularly old. Probably heat, pushing the limits of the cap, or both.

[Toasty]

Re: Sceptre Shlepter

'06 supposedly was the end of the ~bad electrolyte~ era. There's no bulging, and it's a UCC KZH cap, which is very decent quality. Steers me away from a cap problem towards an over-current shutdown being the more likely culprit due to the problems I said before.

Oh BTW, Welcome to the Forums!

Toast

[mmmbuh]

Re: Sceptre Shlepter

Ok, here's the deal. I stuck everything back together to get a better idea what the power led would show through this process. I plugged it in, and got a nice image for about 1 second, and then blankness. The power led stayed constant and blue, just as it does when the monitor is working properly. I played with the buttons on the rear right of the monitor case (settings, volume, etc) and I noticed that after I pressed a button, after 2 seconds or so, the monitor would come on again, then go off after 1 second. Very odd. After I did this a few times, the stupid thing stayed on. So for now, it's working...I'm using it now as I type. BTW, the image is nice and bright, no discoloration or dim areas. I don't know what to think about this. Any ideas? I could guess just a loose connection that I tightened while the case was apart, but if that's the case, then it should have worked as soon as I turned it on again, not after messing with buttons for a while. Any ideas? I really don't want to take it apart again for more board pictures while it is still working...
I appreciate the input you guys are giving to me...
Mike

[mmmbuh]

Re: Sceptre Shlepter

Hey-
instead of a loose connection somewhere, maybe it was the opposite? Could one of those buttons on the back have been stuck so that the contacts of the button were constantly together instead of separating when the button is released? (did that make sense?) and my playing with the buttons got the contacts to separate? Like I said, I'm no expert. Just throwing out ideas...
Mike

[dondrusco]

Re: Sceptre Shlepter

Try to measure resistance at both secondary transformer circuits - this big one near lamp connectors. They have to have the same value.
I had one with one circuit open.

[PlainBill]

Re: Sceptre Shlepter

Ok, here's the deal. I stuck everything back together to get a better idea what the power led would show through this process. I plugged it in, and got a nice image for about 1 second, and then blankness. The power led stayed constant and blue, just as it does when the monitor is working properly. I played with the buttons on the rear right of the monitor case (settings, volume, etc) and I noticed that after I pressed a button, after 2 seconds or so, the monitor would come on again, then go off after 1 second. Very odd. After I did this a few times, the stupid thing stayed on. So for now, it's working...I'm using it now as I type. BTW, the image is nice and bright, no discoloration or dim areas. I don't know what to think about this. Any ideas? I could guess just a loose connection that I tightened while the case was apart, but if that's the case, then it should have worked as soon as I turned it on again, not after messing with buttons for a while. Any ideas? I really don't want to take it apart again for more board pictures while it is still working...
I appreciate the input you guys are giving to me...
Mike

One possibility that comes to mind is that you reduced the brightness. Increasing brightness requires increased current through the CCFLs, which could trip the protection circuit.

PlainBill

[mmmbuh]

Re: Sceptre Shlepter

I decided to plug the monitor into an external switch, to avoid using the power button on the back. It's been 2 days now, and it's worked perfectly. It looks like it was a button issue...maybe. Time will tell. Odd how it acted the same as a cap issue though...
Thanks to all of you that posted advice, if it craps out again, we'll go from there.
Mike