Samsung SyncMaster 204b

[PlainBill]

Re: Samsung SyncMaster 204b

For those who have replaced all the capacitors, but still have trouble with the back light (like me), look for a green resistor-like thing with a f### along side it. These are wire fuses, sometimes called pickle fuses (because they are green?). Unsolder one end and test for continuity. Mine was blown, and a quick trip to an electronics supply store fixed me up. Mine was a 3A unit, yours may be a different value (it was printed on the fuse). Hope that helps!

Not 'pickle fuse', 'Pico fuse'. The name chosen by the manufacturer.

Other than that, your suggestion is sound.

PlainBill

[kking85743]

Re: Samsung SyncMaster 204b

For those who have replaced all the capacitors, but still have trouble with the back light (like me), look for a green resistor-like thing with a f### along side it. These are wire fuses, sometimes called pickle fuses (because they are green?). Unsolder one end and test for continuity. Mine was blown, and a quick trip to an electronics supply store fixed me up. Mine was a 3A unit, yours may be a different value (it was printed on the fuse). Hope that helps!

[john98103]

Re: Samsung SyncMaster 204b

A quick update: first of all THANKS for all the effort in helping try to pinpoint the problem.

I located another identical monitor which had a bad power supply and swaped signal cards; my monitor works fine now. I was going to log all the correct voltages throughout the good board and then compare with the non-working board but my desire to use the working monitor overrode my curiosity and I failed to follow through.

[PlainBill]

Re: Samsung SyncMaster 204b

IC 304 with tab at top:

tab = 1.81V
left pin = 0V
stub = 1.81V
right pin = 3.23V

That's correct for a 1.8 volt LDO regulator.

The symptoms indicate the processor is shutting down. The power supplies appear to be good. The two possibilities are that a power regulator is shutting down, or a processor is sensing problems. I've been able to identify major parts of the circuit.

The area circled in red in the upper left corner is the main regulator. It is a type known as a bucking regulator, this puts a high stress on the caps. One option would be to replace the three caps (2 ea 100uF 25V, 1 ea 100uF, 16V) inside the circle. I don't have high hopes for that.

The area circled in green is the switch for the LCD panel itself. There is no reason to believe that is causing any problem.

There are two areas circled in umber, one on the left side, one on the far right. By the voltages, these are LDO regulators, and are very unlikely to be responsible.

The area on the left circled in yellow represents a mystery. It is clearly a bucking regulator, but there is no identifiable regulator. I suspect it is the 8 pin IC, but the part number is not identifiable. Again, you could try replacing the caps, but I can't offer much hope that would help.

On the right I have circled some pads in gold. That is the area I would expect to find the cable going to the front panel. Which presents a minor mystery - where is the cable to the front panel?

The chip circled in black is the prime suspect. It is the control processor, and because of the white label, is loaded with a custom program for this monitor. And if it can be positively identified as bad, it is pure 'unobtanium'.

PlainBill

[john98103]

Re: Samsung SyncMaster 204b

IC 304 with tab at top:

tab = 1.81V
left pin = 0V
stub = 1.81V
right pin = 3.23V

[PlainBill]

Re: Samsung SyncMaster 204b

with the tab facing up:
left pin = 3.23V
right pin = 2.49V

That would make sense, assuming it's a 2.5 volt regulator.

PlainBill

[john98103]

Re: Samsung SyncMaster 204b

with the tab facing up:
left pin = 3.23V
right pin = 2.49V

[PlainBill]

Re: Samsung SyncMaster 204b

On the left of board, top down:
IC405 9933B / W58A
IC304 17-16 / 05481L (very hard to see)
IC203 MP1583DN / 57975819 / MPS541

On the right side of board, left to right:
IC301 LF25 / 6K1DT546
IC604 CCRB / LM / 393M

also

I've had the power off to the monitor for 6 hours. I get no momentary blue led light any more when first switching on.

IC405 9933B is a SI9938BDY dual P-channel mosfet.
IC304 17-16 / 05481L (very hard to see) No match
IC203 MP1583DN / 57975819 / MPS541 No match
IC301 LF25 / 6K1DT546 is a LF25 2.5 volt regulator
IC604 CCRB / LM / 393M is a LM393M dual comparator

Well, I'd hoped to do better. 3 parts out of 5 ID'd, only one of the three is of interest.

On IC301, the tab and the stub pin are Gnd. What are the voltages on the other two pins?

On IC 304, what are the voltages on each of the pins?

PlainBill

[john98103]

Re: Samsung SyncMaster 204b

On the left of board, top down:
IC405 9933B / W58A
IC304 17-16 / 05481L (very hard to see)
IC203 MP1583DN / 57975819 / MPS541

On the right side of board, left to right:
IC301 LF25 / 6K1DT546
IC604 CCRB / LM / 393M

also

I've had the power off to the monitor for 6 hours. I get no momentary blue led light any more when first switching on.

[PlainBill]

Re: Samsung SyncMaster 204b

Pin 1 = 13.11V
Pin 2 = 3.64V
Pin 3 = 0
Pin 4 = 3.37V
Pin 5 = 0

The LED no longer lights on; previously I would have to have the power off for a short while to get the LED to turn off momentarily, now it won't light up after being powered off for 5 min.

That voltage is essentially correct - it's a 3.3 volt regulator. I've identified a few more ICs on the picture (attached). What are their part numbers?

PlainBill

[john98103]

Re: Samsung SyncMaster 204b

Pin 1 = 13.11V
Pin 2 = 3.64V
Pin 3 = 0
Pin 4 = 3.37V
Pin 5 = 0

The LED no longer lights on; previously I would have to have the power off for a short while to get the LED to turn off momentarily, now it won't light up after being powered off for 5 min.

[retiredcaps]

Re: Samsung SyncMaster 204b

PlainBill wants the voltages from the yellow circled component.

[john98103]

Re: Samsung SyncMaster 204b

first of all; thanks for all the help.

there is an IC just below CN501 (ribbon from CN2) marked IC405 (9933B / W58A). is this the IC I should get voltages from?

[PlainBill]

Re: Samsung SyncMaster 204b

Boards for SyncMaster 204b

Power Supply IP-45130A
Video Board BN41-00620E

Good pictures, thanks. In the upper left corner of the signal card is an IC marked 1501-33. The is a voltage regulator. Pin 1 has a triangle next to it, pin 3 and the tab are both ground. What are the voltages on the other pins (try to get measurements with both power LED on and after the power LED turns off.

PlainBill

[john98103]

Re: Samsung SyncMaster 204b

Boards for SyncMaster 204b

Power Supply IP-45130A
Video Board BN41-00620E

[PlainBill]

Re: Samsung SyncMaster 204b

It's time to direct your attention to the signal card. The power LED turning off is definitely unusual. A good picture of YOUR card would be very helpful.

PlainBill

[retiredcaps]

Re: Samsung SyncMaster 204b

I would suggest you take a good, clear picture of the signal card and attach it to your next post using 'Manage Attachments' (below the text entry area). We're looking for something like 2000 x 2000 pixel resolution.

john98103, we are still waiting for these pics.

[john98103]

Re: Samsung SyncMaster 204b

I'm able to connect all components while monitor is disassembled. I've followed the above directions.

LED lights blue for one second then turns off. CCFL's don't light up, not even momentarily.

Voltages remain as reported previously and are as follows
CN2
#1:PWN-Dim - 0.05-volts
#2,3 & 4 - ground - 0-volts
#5,6 &7 - 13V - 13.11 – volts
#8 - Dim - 0.05 –volts
#9 -on/off -0.01 –volts

CN3 through CN6 all measure zero volts. (grounded at the nearest PS hold down screw and pushing pin through wires)

[PlainBill]

Re: Samsung SyncMaster 204b

with power supply connected to monitor Voltages are as follows
CN2
#1:PWN-Dim - 0.05-volts
#2,3 & 4 - ground - 0-volts
#5,6 &7 - 13V - 13.11 – volts
#8 - Dim - 0.05 –volts
#9 -on/off -0.01 –volts

CN3 through CN6 all measure zero volts. (grounded at the nearest PS hold down screw and pushing pin through wires)

ARGHH!!! We still aren't communicating. Let's do this properly. Part of the problem is I'm not familiar with this monitor. Some configurations make troubleshooting very difficult. Others allow you to hook all parts of the monitor together and still measure voltages.

Setup: Power supply / inverter (PS/I) connected to signal card. Computer with desktop showing connected to signal card. Monitor front panel connected to signal card. It is preferred the CCFLs from the LCD panel be connected to the power supply / inverter. If the design permits it, LCD panel connected to signal card.

Apply power to PS/I. Power LED should come on, if it doesn't, press the power button. CCFLs should light. Measure the voltages on CN2. If the design permitted it, you should see the desktop on the lcd panel. If the CCFLs are not connected do NOT try to measure the voltage on CN3-CN6. There is a very good chance you will destroy your DMM.

If the power LED goes off, changes to amber, etc, report it.

PlainBill

[john98103]

Re: Samsung SyncMaster 204b

with power supply connected to monitor Voltages are as follows
CN2
#1:PWN-Dim - 0.05-volts
#2,3 & 4 - ground - 0-volts
#5,6 &7 - 13V - 13.11 – volts
#8 - Dim - 0.05 –volts
#9 -on/off -0.01 –volts

CN3 through CN6 all measure zero volts. (grounded at the nearest PS hold down screw and pushing pin through wires)