Dell E193FPc - 2 Seconds to Black

[jayoung]

I received a Dell E193FPc that has a 2 seconds to black issue. The top two ccfls light, the bottom two do not light. With four known good ccfls, the result is the same. All of the capacitors appear to be in good shape, I plan to replace them no matter what (1 - 33uf 50V, 2 - 150uf 25V, 2 - 470uf 25V, 1 - 1000uf 16V, and 1 - 1000uf 25V). There are 4 C5706 transistors with the following measurements in circuit. Q209 and Q210 run the top ccfls, Q211 and Q212 run the bottom ccfls.
(black probe-red probe-result(ohms))
Q209 B-C-NO READING, B-E-NO READING, C-E-80.5, C-B-NO READING, E-B-NO READING, E-C-NO READING
Q210 B-C-NO READING, B-E-NO READING, C-E-80.9, C-B-NO READING, E-B-NO READING, E-C-NO READING
Q211 B-C-NO READING, B-E-0, C-E-75.4, C-B-73.5, E-B-0, E-C-NO READING
Q212 B-C-NO READING, B-E-0, C-E-NO READING, C-B-NO READING, E-B-0, E-C-NO READING
Am I correct in saying Q211 and Q212 appear to be shorted? I can take these out of circuit and test if needed. These are the ones working with the ccfls that are not working. From what I have searched for in the forums, it appears that cracked solder joints to the transformers can cause the transistors to short out. I plan to resolder both transformers and replace all four C5706 with C5707. I have the 4 C5707 transistors now, would it be ok to replace the 4 transistors and then check the results before I replace the capacitors when I get them ordered and shipped to me?

Is there anything else that I should be checking and/or replacing?

Thanks in advance for all the help.

[smason]

Re: Dell E193FPc - 2 Seconds to Black

Sounds like you have this well-started.
Yes it sounds like the 2 transistors are shorted, but just so we're clear, please define "no reading" and 0. When you touch both probes together do you actually get 0?

I'd say it's safe to resolder the transformers, and replace the 5707s and test before the caps arrive. I'd also test the other transistors near the 5706s, are there any FETs nearby?

[smason]

Re: Dell E193FPc - 2 Seconds to Black

Oops guess I could have looked at the photos.... duh.

You might want to get pinout info on Q204 and Q203 and check them, as well as Q 205 206 207 and 208 they may be involved in the circuit as well. Too tired to try to trace it at the moment.

[jetadm123]

Re: Dell E193FPc - 2 Seconds to Black

Excluding the large 450V cap, I count 8 small caps. You listed 7 small caps. Did you miss one?

Also, re-solder the the two blue caps between Q209-Q212.

[jayoung]

Re: Dell E193FPc - 2 Seconds to Black

Sounds like you have this well-started.
Yes it sounds like the 2 transistors are shorted, but just so we're clear, please define "no reading" and 0. When you touch both probes together do you actually get 0?

I'd say it's safe to resolder the transformers, and replace the 5707s and test before the caps arrive. I'd also test the other transistors near the 5706s, are there any FETs nearby?

No reading - over the limit - setting of 200 ohms
0 - just like the two probes were touching (actually about 0.3 ohms)

Oops guess I could have looked at the photos.... duh.

You might want to get pinout info on Q204 and Q203 and check them, as well as Q 205 206 207 and 208 they may be involved in the circuit as well. Too tired to try to trace it at the moment.

Q203 and Q204 are BD5N18 - I cannot find the info that I can check - it has 4 pins on each side

Q205 B-C-3950, B-E-8060, C-E-4190, C-B-3950, E-B-8050, E-C-4190
Q206 B-C-3950, B-E-8010, C-E-4140, C-B-3950, E-B-8000, E-C-4140
Q207 B-C-7170, B-E-8020, C-E-38300, C-B-38500, E-B-8030, E-C-8090
Q208 B-C-7200, B-E-7960, C-E-38600, C-B-39400, E-B-7980, E-C-8030

Excluding the large 450V cap, I count 8 small caps. You listed 7 small caps. Did you miss one?

Also, re-solder the the two blue caps between Q209-Q212.

I did not list the start-up cap (?) 22uf 50V

Should I do any checks on the transformers? One of them obviously works since two of the 4 bulbs light initially.

[retiredcaps]

Re: Dell E193FPc - 2 Seconds to Black

No reading - over the limit - setting of 200 ohms
0 - just like the two probes were touching (actually about 0.3 ohms)

A multimeter ALWAYS gives a reading. "1" IS a reading. "1" on the left hand side of the multimeter means it is out of range for the chosen range. So if your multimeter is set to 200 ohms, it means the reading is greater than 200 ohms.

When testing for a shorted component, readings less than 30 ohms suggest the component might be shorted. If the multimeter shows "1" (i.e. ohmns > 200), then we know it is likely not shorted.

When you report readings, we always want the actual reading. The difference between 0 and 0.3 ohms is significant.

Q205 B-C-3950, B-E-8060, C-E-4190, C-B-3950, E-B-8050, E-C-4190
Q206 B-C-3950, B-E-8010, C-E-4140, C-B-3950, E-B-8000, E-C-4140
Q207 B-C-7170, B-E-8020, C-E-38300, C-B-38500, E-B-8030, E-C-8090
Q208 B-C-7200, B-E-7960, C-E-38600, C-B-39400, E-B-7980, E-C-8030

Anytime you report a multimeter reading, always include the measurement unit. We can only guess at what unit of measurement is above. If it is ohms, then the above components are likely not shorted.

I did not list the start-up cap (?) 22uf 50V

This small startup cap plays an important role in the SMPS startup process and can often fail without any signs of bloating.

Should I do any checks on the transformers?

Yes. See

https://www.badcaps.net/forum/showpo...1&postcount=14

PS. Excellent clear focused pictures.

[jayoung]

Re: Dell E193FPc - 2 Seconds to Black

Yes. See

https://www.badcaps.net/forum/showpo...1&postcount=14
.

I'm new to testing electronics and don't quite understand the measuring of the transformer. The youtube video in that link no longer works. In the link, it states "Number the pins on the transformers anyway you like." I have 2 pins on one side and 7 pins on the other side of the 80LL15T-7-YS 0523 transformer. Do I number from 1 to 9 or just 1 to 7 on the one side? The only information that I could find on the pin out of the transformer was a photobucket image stating "250 Ohms on the secondary side winding (pin 7 and 9)" I get 250 ohms PT202 and 249 ohms on PT201. Numbering from 1 - 9 and testing would give 36 readings. Is this correct?

I just don't want to replace the C5707's and then have them short out because of a problem with something else.

Thanks again in advance for the quick and knowledgeable responses.

[PlainBill]

Re: Dell E193FPc - 2 Seconds to Black

I'm new to testing electronics and don't quite understand the measuring of the transformer. The youtube video in that link no longer works. In the link, it states "Number the pins on the transformers anyway you like." I have 2 pins on one side and 7 pins on the other side of the 80LL15T-7-YS 0523 transformer. Do I number from 1 to 9 or just 1 to 7 on the one side? The only information that I could find on the pin out of the transformer was a photobucket image stating "250 Ohms on the secondary side winding (pin 7 and 9)" I get 250 ohms PT202 and 249 ohms on PT201. Numbering from 1 - 9 and testing would give 36 readings. Is this correct?

I just don't want to replace the C5707's and then have them short out because of a problem with something else.

Thanks again in advance for the quick and knowledgeable responses.

You are over thinking the problem. You have already tested the transformers and they are probably good (249 vs 250 ohms).

In essence, a transformer can be thought of as a black (or yellow) box with a number of pins. Some of the pins aren't connected to anything. Some are connected to another pin by a short coil of heavy wire (sometimes three pins may be connected by two coils of wire). And two pins will be connected by a long coil of very fine wire. That is the secondary, and they are prone to failure - either from shorting or the wire breaking. (Some transformers have two or more secondaries).

By measuring the resistance from pin 1 to pins 2-9, from pin 2 to pins 3-9, pin 3 to 4-9, etc you can identify which pins are connected together, which is the secondary, and if the secondaries match. On inverters the primary (or primaries) will have very low resistance - less than an ohm.

PlainBill

[jayoung]

Re: Dell E193FPc - 2 Seconds to Black

Thanks for all the replies. Hopefully this weekend I will have time to be able to replace the 4 - C5707s and re-solder the two transformers and the two blue caps between Q209-Q212. I will check the results and replace the 8 capacitors when they arrive. I will update when that is complete. Thanks again to everyone.

[jayoung]

Re: Dell E193FPc - 2 Seconds to Black

I finally got the time to work on this monitor again this evening and wanted to give an update to it's status. I replaced all 8 of the caps and all four of the C5707s. I re-soldered both transformers and the two ceramic capacitors. With everything back together, I am writing this post using the monitor while I test it for a few hours. Thanks to everyone on this forum and especially to the ones that replied to my original post (smason, jetadm123, retiredcaps, and PlainBill).

[pm03]

Re: Dell E193FPc - 2 Seconds to Black

nice job!

[niranjanmondal]

Re: Dell E193FPc - 2 Seconds to Black

Man I am very much Upset My Lcd is not working properly.
the same 3 seconds issue of Benq Lcd Moniter.
_______________________________________
I think the picofuse is blown off ( not sure )
Because last time when I was facebooking My monter screen went extreme Bright and truned off .
Then I re stated my pc and seen the bios for 3 seconds and Microsoft logo for 3 seconds
then no response from the lcd.
when i pressed the power button on\off the screen was normal visible but goes off again after 3 seconds.
________________________
There any Idea what posibly had happned ( picofuse )

[PlainBill]

Re: Dell E193FPc - 2 Seconds to Black

Man I am very much Upset My Lcd is not working properly.
the same 3 seconds issue of Benq Lcd Moniter.
_______________________________________
I think the picofuse is blown off ( not sure )
Because last time when I was facebooking My monter screen went extreme Bright and truned off .
Then I re stated my pc and seen the bios for 3 seconds and Microsoft logo for 3 seconds
then no response from the lcd.
when i pressed the power button on\off the screen was normal visible but goes off again after 3 seconds.
________________________
There any Idea what posibly had happned ( picofuse )

The picofuse is NOT blown; if it were you wouldn't be getting any backlights. That is elementary.

The usual problem is the solder joints on the transformers crack. This causes the transistors driving the transformers to short. You may have a different problem.

Disconnect all the CCFL leads except the one to CON201. Turn on the monitor. Do the backlights turn on for two seconds?

Disconnect the CCFL lead from CON201 and reconnect the one to CON202. Turn on the monitor. Do the backlights turn on for two seconds?

Disconnect the CCFL lead from CON202 and reconnect the one to CON203. Turn on the monitor. Do the backlights turn on for two seconds?

Disconnect the CCFL lead from CON203 and reconnect the one to CON204. Turn on the monitor. Do the backlights turn on for two seconds?

If all CCFLs but one turn on, you have a bad CCFL or CCFL wiring.

If both CCFLs in a pair turn on, while neither in the other pair turn on, you have the usual problem. Replace Q203 / Q204 on the side that is not lighting.

Check Q209 / Q210 or Q211 / Q212 on the 'dead' side for shorts. If any are shorted, replace all.

Resolder all pins on PT201 and PT202.

Replace all electrolytic caps except C904

PlainBill