Samsung Syncmaster 245BW

[Aruba]

Originally Posted by cloepula

Aruba??
Flickering solved or you gived up on this?

Thanks for keeping interested on my monitor. No I have not given up yet but
have been busy at work. What I was able to do was to replace the ICE3B0365J controller with an ICE3B0365L part as that was only what I have
for replacement and I didn't see enough differences between the two parts.
After power on this new part had a catastrophic event happen to it and it
also took a sot-23 zener diode with it. This diode has a bubble on it and I
can no longer read the markings this part. I don't have the designator at this
moment but will put it up on another response and hopefully someone could
help me identify what the value is for this zener diode. Digikey has the exact
part ICE3B0365J so I will place an order along with the PFC controller
TDA4863.

[Aruba]

Originally Posted by cloepula

I see you have an oscilloscope.
This days me to bouth my first scope, is a cheap one, and second hand to, and have only one probe 10x for now. Starting to make some measurment with scope, but must buy a 100x probe, because my scope is only 20v. Picoscope adc200/50. 25mhz. For starting and investigating on 100khz smps power supply i think will be good anough. Can you give me some advice on this?

You should be able to find many advice on the web. Using your 25Mhz scope
you should be able to measure just about any signal you would want in a
power supply. One word of caution, When you are measuring anything on the
primary (line) side make sure your scope is isolated. You can do this by
placing an (1:1) isolation transformer between the AC power and your scope
power. You would also need 100X probes if you want to measure the high
voltage waveforms of the switching transistors/FETs which could be as high
as 1000Vp-p. I like using the analog scopes like a Tektronix 465 scope. If you
could find one of those cheap then you got everything you would ever need.
I have a portable Tektronix scope like the one shown on the picture which I
find handy and since it also works off of battery power I am completely
isolated from the equipment being tested and no isolation transformer is
necessary when I measure the primary waveforms.

[cloepula]

My scope working on power adapter, from 230v ac to 12v dc, and is conected to pc with paralel cable. The manual say thet ground from scope is conected to
pc ground. So in this case maybe will be beter to run Pc, monitor, and scope with ups when measurment is done on hi voltage circuit. Maybe one day i will buy a isolation transformer for complete system, will need about 400w of power. So a 500w will be one option to buy, and i dont know the cost of this transformer.

[cloepula]

think thet maybe an ups is an isolation transformer to, i dont know what for shure if it is when is conected to ac plug in the wall, maybe will be good to find some way to measure this and be completly shure

[cloepula]

Problem is in equipment grounding and 0 wire ?
My instalation at home dont have 3 wire instalation, only 2 wire is present, and the ground is bridged on 0 to be grounded in hi voltage transformer station. So if a resistance betwen a pc ground and outlet 0 or ground is infinite maybe this will be anough to isolate the equipment .

[PlainBill]

Originally Posted by cloepula

Problem is in equipment grounding and 0 wire ?
My instalation at home dont have 3 wire instalation, only 2 wire is present, and the ground is bridged on 0 to be grounded in hi voltage transformer station. So if a resistance betwen a pc ground and outlet 0 or ground is infinite maybe this will be anough to isolate the equipment .

Running the PC and the scope from an UNPLUGGED UPS while the power supply is plugged into an AC socket will provide adequate isolation, but the PC chassis will be at something like 1/2 or 2/3 of line voltage. Very dangerous, the PC must be on a non-conductive surface, and DON'T touch it while the power supply is live.

PlainBill

[Aruba]

Originally Posted by Aruba

Thanks for keeping interested on my monitor. No I have not given up yet but
have been busy at work. What I was able to do was to replace the ICE3B0365J controller with an ICE3B0365L part as that was only what I have
for replacement and I didn't see enough differences between the two parts.
After power on this new part had a catastrophic event happen to it and it
also took a sot-23 zener diode with it. This diode has a bubble on it and I
can no longer read the markings this part. I don't have the designator at this
moment but will put it up on another response and hopefully someone could
help me identify what the value is for this zener diode. Digikey has the exact
part ICE3B0365J so I will place an order along with the PFC controller
TDA4863.

Can someone with a Samsung Syncmaster 245BW identify on the power supply board the following two zener diode marking on the part ?

- DZB871
- DZB872

Both are SOT-23 packages and start with the "Y" prefix. The next one or two
digits is what I need.

Thanks in advance.

[technicalspecialist]

I quickly took the back off my 245B. My camera isn't good enough to see up that close without going blurry so using a magifying glass and torch, I could just make out that DZB872 says Y63* on it and DZB871 says Y11. *the 3 appears to be turned 90 degrees forward so it's like the top points to the 3 on a clock face.

[technicalspecialist]

If you still don't manage to fix it, why not try modifying the +12V of an ATX PSU to output 24V if possible for the backlight inverter. You already have 5VSB and +5V with enough amps for the logic board.

[technicalspecialist]

Originally Posted by technicalspecialist

I quickly took the back off my 245B. My camera isn't good enough to see up that close without going blurry so using a magifying glass and torch, I could just make out that DZB872 says Y63* on it and DZB871 says Y11. *the 3 appears to be turned 90 degrees forward so it's like the top points to the 3 on a clock face.

Actually after looking again, the 3 is turned 90 degrees backwards so the top points to the 9 on a clock. It probably doesn't matter which way it points anyway...

[technicalspecialist]

After Googling SOT-23 Y63, I found this PDF: http://www.reparaturtipps.tv/diverses/SMD-PHILIPS.pdf It has the marking codes and type numbers.

[Aruba]

Originally Posted by technicalspecialist

Actually after looking again, the 3 is turned 90 degrees backwards so the top points to the 9 on a clock. It probably doesn't matter which way it points anyway...

Thanks for looking this up.
Regarding DZB872 which has the Y6 marking and a 3 laying down on its side,
I'm thinking that it is a Y6 (18V, 0.3W, 5%) zener. The 3 on its side may mean
a different code like the batch number. Why would you intentionally print the
"3" sideways if there is plenty of space to print it in the same orientation as the
Y and the 6 ? By the way Y63 according per the chart is an 8.2V zener.
DZB871 with its Y11 marking should be a 30V, 0.3W, 5% zener according to the
chart. Need to get these parts and report back.

[lucky13]

Here are the close ups from mine:

Y6 and
Y11

[Aruba]

Originally Posted by lucky13

Here are the close ups from mine:

Y6 and
Y11

Thanks Lucky13 ! We now have confirmation that they are Y6 (18V) and
Y11 (30V). Let's hope those are the correct zener values. I have leaded
versions on these zener diode values so I should be able to test it out
tomorrow when using the old ICE3B0365J controller. If everything works
out I should be back to a flickering display when turned on.

[Aruba]

Originally Posted by Aruba

Thanks Lucky13 ! We now have confirmation that they are Y6 (18V) and
Y11 (30V). Let's hope those are the correct zener values. I have leaded
versions on these zener diode values so I should be able to test it out
tomorrow when using the old ICE3B0365J controller. If everything works
out I should be back to a flickering display when turned on.

Update: replaced the damaged 18V and 30V zener diodes with leaded ones
and placed the original ICE3B0365J back in its place and the unit powered up
normal with no sparks this time. The flickering now is at a much slower rate
and somewhat random. Before the flickering seems to happening every half a
second but now it flickers very seldom maybe once a minute and then at
other times once every 2 minutes. The 24V now measures a solid 24.2V with
a DVM but looking at the 24V with a scope it shows me it is still varying
between 24-21V but at a very high rate. While checking the bulk 450V
capacitor voltage I saw it was at a solid 400VDC voltage but then rechecking
it again at a later time it was back to the oscillating voltage seen previously.
Now that I am back to the original state I can check the condition of the PFC
controller (TDA4863). To be continued.............

[cloepula]

Me to tested this two diodes, and was ok. Used a lab power supply and a serial resistor with diodes. Think was a 1 kohm resistor, and both zener start to drow curent near to 18v and 30v.
This flicker problem is more serious thet was my problem with no power at all.

[Aruba]

Originally Posted by cloepula

Me to tested this two diodes, and was ok. Used a lab power supply and a serial resistor with diodes. Think was a 1 kohm resistor, and both zener start to drow curent near to 18v and 30v.
This flicker problem is more serious thet was my problem with no power at all.

Got some new TDA4863 - PFC controllers in and replacement of it did not fix
the problem. The flickering is still present and while measuring the power
factor it is only around 0.65 vs 0.97 that I was able to measure from a
co-worker's similar monitor. He is not willing to let me take it apart and take
measurements on the power supply board though . I am kind of stuck
now as what to do next. I will recheck all the components around this
controller one more time and see if I may have missed something. Any other suggestions ?

[cloepula]

Originally Posted by Aruba

Got some new TDA4863 - PFC controllers in and replacement of it did not fix
the problem. The flickering is still present and while measuring the power
factor it is only around 0.65 vs 0.97 that I was able to measure from a
co-worker's similar monitor. He is not willing to let me take it apart and take
measurements on the power supply board though . I am kind of stuck
now as what to do next. I will recheck all the components around this
controller one more time and see if I may have missed something. Any other suggestions ?

This will be the only way to find out what is wrong with this power supply.
Me to take it apart completly and measure all component one by one. There was somme example in my repair history when even this last resort metod didnt push the piece of equipment to work, but if you dont do it you will never know. One time when i was repairing cheap 350w pc power supply thet have a problem in +5v output, was unstable from 5.3v to 6v and everithing else was ok. After taking all measurement on the component inside this power supply and didnt found anithing wrong, i let it apart and give up . Then maybe in 10-15 days on another diferent pc power supply without any signs of activity found a npn transistor burned and a electrolit with hi esr. When changing transistor and electrolite was done, the supply was alive, but the +5v was unstable just like on the first supply. The joy of this was thet i didnt have exactly the same transistor and i put inside the supply one similar. When change this similar transistor with exactly the same as was the original the +5v become ok. Changing on the first supply the +5v otuput transistor with new one the +5v become ok to. The old transistor i test and was ok when testing with dmm but didnt work corectly when was used in circuit.

[zeha]

Hello,

Thanks to Cloepula.
My monitor is fixed.
In my case only QM802 an resistor RB805 defect.
I have drawn the cuircuit by my own.
It missing something because i can't read or meassure the parts.
Somebody to complete this?


Cheers
Harrie

[Aruba]

Originally Posted by cloepula

This will be the only way to find out what is wrong with this power supply.
Me to take it apart completly and measure all component one by one. There was somme example in my repair history when even this last resort metod didnt push the piece of equipment to work, but if you dont do it you will never know. One time when i was repairing cheap 350w pc power supply thet have a problem in +5v output, was unstable from 5.3v to 6v and everithing else was ok. After taking all measurement on the component inside this power supply and didnt found anithing wrong, i let it apart and give up . Then maybe in 10-15 days on another diferent pc power supply without any signs of activity found a npn transistor burned and a electrolit with hi esr. When changing transistor and electrolite was done, the supply was alive, but the +5v was unstable just like on the first supply. The joy of this was thet i didnt have exactly the same transistor and i put inside the supply one similar. When change this similar transistor with exactly the same as was the original the +5v become ok. Changing on the first supply the +5v otuput transistor with new one the +5v become ok to. The old transistor i test and was ok when testing with dmm but didnt work corectly when was used in circuit.

We are back ! Was busy at work so this monitor had to wait. For those that have not given up I have good news to report. If your 245B monitor problem is not related to QM802 or RB805 and you have a flickering monitor then the following might help you.
I did not have the 82uF, 450V bulk cap or sometimes referred to as the hold-up cap that allows a line dropout of maybe a 1/2 cycle to go by without
you noticing there was a line dropout but decided to remove it today and
measure it. I do not have an ESR meter but do have a cap meter and
surprisingly it measures 0 uF. I was able to find a 270uF, 450V at hand and
installed it on the board at location CP803 and the monitor turned on with no
more flicker ! This 82uF, 450V cap is from "Samwha".
now that the monitor is working correctly I measure a solid 386VDC on this
cap and my power factor meter shows the power factor is 0.97 versus 0.65
when it was flickering. The 24V output is also measuring a steady 24V.

Another success story regarding BAD CAPS.
Thanks to everyone's help here.