Samsung Syncmaster 172N with fried resistors under T1 - No backlight

[EGuevarae]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

See the other pics. The one of the whole board, with the glare. That mark does not appear.

There's a nice plugin for Firefox called Image Zoom. Really helpful, for us elderly.

http://imagezoom.yellowgorilla.net/

Nice plug in.I have FF 3.x installed but I can't get used to it...... it uses less memory than Internet Bloatxplorer 7 and is faster, but I just can't. I think I will now ....

[Toasty]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

Yup, it's toast (LOL) then. Time for a new transformer.

[EGuevarae]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

Yup, it's toast (LOL) then. Time for a new transformer.

Well Toast says the T is toasty...no wait, Toasty says the T is Toast. I'm confused.......
Anyway, I finally did something right with that ohmmeter of mine ...

Well. Now the $64,000 question : how is this related to the three dead resistors?

• They fried the T
• The T fried them
• They were so in love with each other that they committed suicide ala Shakespeare together.
• Were they murdered by another jealous component?
• Bad coincidence both things died at the same time

[Toasty]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

Dunno, but for $22 you can get one from the UK. You can also email them first with the XFMR model number 8TC00149 and what unit it came from. They should be able to confirm this is the one you want.

http://www.lcdinverter.co.uk/MHEEL19-043.htm

IIRC, there is also a company from Taiwan that sells these direct. I can't recall the site, but I bounced into it from an audiophile site a while back. They make coils and XFMRs for tons of equipment.

[Toasty]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

>>The readings between pink pins (primary) is 0 ohms.<<
You mean shorted, correct? Same as if you put the meter probes together.

>>...how is this related to the three dead resistors?<<
Are you sure the 3 resistors were 3 x 10k?

>>shorted, the readings between one pink and one blue is 480.<<
Which pink pin and which blue pin?
->Going top to bottom, Pink are 1 & 2, Blue are 4 & 5.

No readings any other way, correct?

Secondary is open and primary is open, correct?


If you follow the traces I made, you can see that the resistors are connected to BOTH transformers "un-hot" or "neutral" leg - the yellow trace. The purple trace is GROUND. The resistors are across the neutral legs to ground. A failure in the transformer (short or open) placed enough voltage & current across those resistors to fry them.

[EGuevarae]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

>>The readings between pink pins (primary) is 0 ohms.<<
You mean shorted, correct? Same as if you put the meter probes together.

Yes, as if I just cross the probes.

>>...how is this related to the three dead resistors?<<
Are you sure the 3 resistors were 3 x 10k?

Yes, I am. They were measured before they fell apart on their own (they were almost falling when I got the board). The three measured 10 on the 20K scale, so I guess that make them 10K each.

>>shorted, the readings between one pink and one blue is 480.<<
Which pink pin and which blue pin?
->Going top to bottom, Pink are 1 & 2, Blue are 4 & 5.

Pick any pin you like against any other pin you like. All of them are crossed and read 480 (in the suspected bad):
1-2
1-4
1-5
1-2
etc.

No readings any other way, correct?

Reads all over the place on the bad one. On the good one, 0 between the pinkies and 480 between the blues, and nothing between blues or pinks.

Secondary is open and primary is open, correct?

?? Dunno... Closed would be a better term, as they are all connected? I dunno. Please help here. Open would mean no contact between pinkies (or blues, if it is the secondary), right?
Man, I guess that "the more I learn the less I know" fits tightly here...

If you follow the traces I made, you can see that the resistors are connected to BOTH transformers "un-hot" or "neutral" leg - the yellow trace. The purple trace is GROUND. The resistors are across the neutral legs to ground. A failure in the transformer (short or open) placed enough voltage & current across those resistors to fry them.

So T killed Rs.... case solved. Let's put T to jail for a three count murder in first degree charges ....

[Toasty]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

^^^^
-Okay

-Overheated resistors rise in resistance, so your 10k readings may be inaccurate. I was looking for your answer to be about the markings on them.

-Okay. Your initial response was ONE pink and ONE blue, I was trying to determine which ones. It should have been ALL.

-Okay

-Okay. Was referring to the ONE pin mix up. Questioning if one was shorted to secondary, were either the primary or secondary open? Done.

That bunch of 5 from eBay surely would have netted you a good one or two.

Note that the manufacturer is no longer using these XFMRs on this board. They've gone to the smaller units and there are 4 of them. See Post #3 on the thread.

[EGuevarae]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

^^^^
-Overheated resistors rise in resistance, so your 10k readings may be inaccurate. I was looking for your answer to be about the markings on them.

No markings (visible). They measured 10k in both of the units, so I assumed they were 10k. Besides, the guy I mentioned (see Post #4) measured the same, used a single 33k resistor. He didn't mention how he connected it, and I have not been able to get in touch with him so far to get this info.
I could be wrong, so I'm hunting for a similar unit (working) to see how them measure there.

-Okay. Your initial response was ONE pink and ONE blue, I was trying to determine which ones. It should have been ALL.

I just tested one of each side (the top pink and the top blue) initially. Then, when you asked, I noticed that I was getting readings all over the place. So the answer was ALL. Sorry, I guess I should have done this since the beginning. My bad.

-Okay. Was referring to the ONE pin mix up. Questioning if one was shorted to secondary, were either the primary or secondary open? Done.

If they were open, I should have no readings between the two pinks or the two blues, right? Please confirm, as this is my idea of an open pri/sec, and if I'm wrong I want to know. Thanks

That bunch of 5 from eBay surely would have netted you a good one or two.

The 5 lot was for a NEC 1830. I haven't checked if they are the same. I have one of them dead, I could just take off the Transformer and if not shorted or open (please confirm the open question above) I could use it on this monitor. The inverter has two, and I just need one, so maybe I can get it from there

Note that the manufacturer is no longer using these XFMRs on this board. They've gone to the smaller units and there are 4 of them. See Post #3 on the thread.

Is this better (I mean, using 4 smaller, one for each CCFL, instead of two bigger, one for each pair of CCFLs)? Also, the connectors are different : mine has a wider connector, 4 pins, where both lamps connect. The one in post #3 has 4 individual connectors, more standard (I have seen that connectors a lot).

[Toasty]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

So with this one you can probably fix the other display? Or vice-versa?

Resistors not the problem Easy Fix. XFMR is problem now confirmed. Put the transformer down and step away!

Connectors on board different, but boards have same model numbers.

[EGuevarae]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

Transformers are not the same between this unit and the 1830. It is now confirmed.
I got a melted (yes, melted.... beneath the big cap in the AC input) PSU like mine today. I desoldered both transformers but had not tested them yet. If tested good, I'll put one in the PSU I'm working on to see what's going on. Also, it had the same 3 resistors under the T that failed on mine, and now it is confirmed too that it is a chain of 3 resistors, 10k each. Again, no markings (not visible ones).

[EGuevarae]

Re: Samsung Syncmaster 172N with fried resistors under T1 - No backlight

Transformers are not the same between this unit and the 1830. It is now confirmed.
I got a melted (yes, melted.... beneath the big cap in the AC input) PSU like mine today. I desoldered both transformers but had not tested them yet. If tested good, I'll put one in the PSU I'm working on to see what's going on. Also, it had the same 3 resistors under the T that failed on mine, and now it is confirmed too that it is a chain of 3 resistors, 10k each. Again, no markings (not visible ones).

Transformers were shorted. Common failure on this model?
Well, I got tired of it, and did this :
1.- Removed the jumpers to the inverter section, ALONG WITH ALL THE COMPONENTS ON THAT SIDE, FROM THE TOP OF THE BOARD ONLY.
2.- Wired a Mitsubishi DiamondPoint VL150 inverter and secured it in the space now empty. It fits pretty well. Replaced 2 hermei caps on the input of the inverter by two Nichicons before the install.Under it, a plastic film like the one beneath the PSU isolates it from physically touching the PSU/Inverter board.
3.- Assembled and tested the unit: light is on, bright control works, and I'm happy.
I still have to mess with one unit. This one has no shorted Transformers, just the 3 resistors burned. On this one, I'm gonna make the install-one-33k-rez experiment. If the inverter side dies, now I know what to do.....