Sceptre X9G-Komodo II* blinking power light

[alexanna]

Re: Sceptre X9G-Komodo II* blinking power light

The proper transistors are Rohm 2SC4672. Digikey has them as 2SC4672T100QCT-ND. There are a number of reasons they can short. You have already identified one - the tuning capacitor. Another is a bad solder joint on the transformers, and there is a zener diode that has been blamed.

The 2PD602A isn't a good substitute. It's rated at 500 ma vs 3A for the 2SC4672.

PlainBill

I think you miss understood my post the 2SC4672T100QCT had been replaced along with A bunch of soldering redone, And the DK transistors continued to short.
They quit failing after I replaced the two SOT346 transistors I circled in the picture

[PlainBill]

Re: Sceptre X9G-Komodo II* blinking power light

I think you miss understood my post the 2SC4672T100QCT had been replaced along with A bunch of soldering redone, And the DK transistors continued to short.
They quit failing after I replaced the two SOT346 transistors I circled in the picture

You are right, I certainly did misunderstand you. And I now suspect I know what was happening. If those are tied into the two FETs above them, they probably handle level shifting of the drive signal. Now to see if that is related to a problem I have been having on another monitor...

Thanks for the correction.

PlainBill

[jagibbs]

Re: Sceptre X9G-Komodo II* blinking power light

I know months have gone by since the last post in this thread, but my slightly different issue with the same board could potentially help someone in the future (if I can get it fixed).

Like others, my monitor was turning on, then going black after 1-2 seconds. I found a cracked C10 film resistor and some board discoloration (from excessive heat) near T1. I replaced ALL of the electrolytic caps with Panasonic FM series and also the two film caps (C10 and C21). Now my monitor stays on, however I may still have a problem.

I find that component T1 is getting very hot very quick, whereas component T2 is staying cool. I think these are some sort of inverters/transformers. My thought is that the overly hot T1 is what caused my C10 cap to fail. If I do nothing else, it will just fail again. Any ideas of what I should probe or check next? I'm not sure what to probe to begin troubleshooting.

I only have basic electronic experience.

[jetadm123]

Re: Sceptre X9G-Komodo II* blinking power light

I know months have gone by since the last post in this thread, but my slightly different issue with the same board could potentially help someone in the future (if I can get it fixed).

Like others, my monitor was turning on, then going black after 1-2 seconds. I found a cracked C10 film resistor and some board discoloration (from excessive heat) near T1. I replaced ALL of the electrolytic caps with Panasonic FM series and also the two film caps (C10 and C21). Now my monitor stays on, however I may still have a problem.

I find that component T1 is getting very hot very quick, whereas component T2 is staying cool. I think these are some sort of inverters/transformers. My thought is that the overly hot T1 is what caused my C10 cap to fail. If I do nothing else, it will just fail again. Any ideas of what I should probe or check next? I'm not sure what to probe to begin troubleshooting.

I only have basic electronic experience.

A good focused photo of the top and bottom of YOUR power board would be helpful as there are different revisions of your board. It's hard to point out things for you to check if members have nothing to look at. Use the "manage attachments" button when posting photos.

[alexanna]

Re: Sceptre X9G-Komodo II* blinking power light

I know months have gone by since the last post in this thread, but my slightly different issue with the same board could potentially help someone in the future (if I can get it fixed).

Like others, my monitor was turning on, then going black after 1-2 seconds. I found a cracked C10 film resistor and some board discoloration (from excessive heat) near T1. I replaced ALL of the electrolytic caps with Panasonic FM series and also the two film caps (C10 and C21). Now my monitor stays on, however I may still have a problem.

I find that component T1 is getting very hot very quick, whereas component T2 is staying cool. I think these are some sort of inverters/transformers. My thought is that the overly hot T1 is what caused my C10 cap to fail. If I do nothing else, it will just fail again. Any ideas of what I should probe or check next? I'm not sure what to probe to begin troubleshooting.

I only have basic electronic experience.

If you disconnect the CCFLs on the coil that's getting hot do you experience 2 sec to black?
If you get 2 sec to black with the CCFLs disconnected, I would suspect a wiring problem on the hot side of the CCFLs.
Photos would be nice.

[PlainBill]

Re: Sceptre X9G-Komodo II* blinking power light

I know months have gone by since the last post in this thread, but my slightly different issue with the same board could potentially help someone in the future (if I can get it fixed).

Like others, my monitor was turning on, then going black after 1-2 seconds. I found a cracked C10 film resistor and some board discoloration (from excessive heat) near T1. I replaced ALL of the electrolytic caps with Panasonic FM series and also the two film caps (C10 and C21). Now my monitor stays on, however I may still have a problem.

I find that component T1 is getting very hot very quick, whereas component T2 is staying cool. I think these are some sort of inverters/transformers. My thought is that the overly hot T1 is what caused my C10 cap to fail. If I do nothing else, it will just fail again. Any ideas of what I should probe or check next? I'm not sure what to probe to begin troubleshooting.

I only have basic electronic experience.

I see several possible reasons for this.

1. A shorted secondary winding in the transformer.

2. A bad coupling cap between the driver transistor and the primary winding.

3. A bad cap on the output.

4. A bad CCFL.

As jetadm has suggested, pictures will really help.

PlainBill

[jagibbs]

Re: Sceptre X9G-Komodo II* blinking power light

Wow, wasn't expecting as many replies so quick! Thanks.

I can get some pictures of my board tonight. In the meantime my board is the exact same as shown in Hennegan's post on 01-22-2011, 06:50 PM (same board part number and rev). All of the components look identical also. well, they did until I replaced the caps with new ones.

alexanna, "by 2 seconds to black" what are you suggesting/asking? My monitor is not going black any longer now that I've replaced all the caps, but T1 is getting much hotter than T2 during operation (measured with finger and thermal gun...) I have not left it on much longer than 30-40 seconds to see how hot it would eventually get. I suspect a hot transformer is not normal?

I did order 4 new transistors (Q6, Q7, Q11, and Q12) from Digikey, but have not installed them yet. I'm not sure what and where to try probing first with the meter. I can try comparing readings from the cool transformer to the hot one as a start. I have access to a really nice de-soldering/rework station so pulling components to check them is easy for me.

If it is faulty windings, is there a source for a replacement, or am I out of luck? I don't think having them custom rewound is going to be cost efficient. Wouldn't even know what the specs are to rewind them anyway.

[jagibbs]

Re: Sceptre X9G-Komodo II* blinking power light

Couldn't edit my post above to add the pics, so here they are. IGNORE the third pic (the values) in this post, and see my next post instead. I measured on both T1 and T2 (T1 is the one running hot). I arbitrarily labeled the pins A through H similarly for both components as seen when looking at the bottom of the board. There seems to be some drastic differences when measuring from any of the pins in the row of A through E across to G or H. Much higher resistances on the properly working transformer (T2). Could these be due to faulty windings, or could my measurements be biased by other components on the board?

[jagibbs]

Re: Sceptre X9G-Komodo II* blinking power light

Ignore IMG_3677 in my previous post and use this instead. I rechecked the board and all measurements across T2 (good component) measure at least 1 Megaohm, not 21kOhm as my earlier table indicated. New table shown below. Note the very last value should read 307 ohms, not 307 kOhms.

Also I measure 648 Ohms across D1 and 20.7 kOhms across D4.

I also see differences in resistance measurements across my transistors. Se my post below for values.

[retiredcaps]

Re: Sceptre X9G-Komodo II* blinking power light

What is the part number for your inverter transformer?

PS. Those are excellent photos!

[jagibbs]

Re: Sceptre X9G-Komodo II* blinking power light

And I promise this is my last set of measurements for the night. Here are my resistance measurements across transistors Q6, Q7 and Q11, Q12. Diagrams are looking down at the transistors on the board as in my earlier picture.

[jagibbs]

Re: Sceptre X9G-Komodo II* blinking power light

The only numbers printed on my inverter transformers (assuming you mean T1 and T2) are:

2600059016
JER 0529

and

2600059016
JER 0520

[retiredcaps]

Re: Sceptre X9G-Komodo II* blinking power light

Here are my resistance measurements across transistors Q6, Q7 and Q11, Q12.

Q6 and Q7 might be shorted between A-C at 72 ohms. I classify 72 ohms as in the "gray" area. It also might be reading low because the measurements are done in circuit.

[retiredcaps]

Re: Sceptre X9G-Komodo II* blinking power light

2600059016
JER 0529

https://www.badcaps.net/forum/showthread.php?t=5552

[jagibbs]

Re: Sceptre X9G-Komodo II* blinking power light

https://www.badcaps.net/forum/showthread.php?t=5552

Yeah, I came across that thread yesterday. Don't think the guy ever figured it out. A few suggestions were given for places that can wind transformers to spec. Problem here is we don't know the exact specs.

This place manufactures many that look similar to the ones on these boards, not that you can buy one from them. They supply to MFGR's in massive quantities. The 4th one in on the top row of the picture for CCFL inverter transformers looks suspiciously familiar and has the same number of windings.

http://okerda.en.alibaba.com/product...ansformer.html