Samsung 2493 HM issue

[pamr4]

Re: Samsung 2493 HM issue

Please measure the 3 resistors placed around the big cap (i think is 82micro 400-450V?). The resistors are supose to be noted on PCB something like RM801, bla bla. Post readings.

[PlainBill]

Re: Samsung 2493 HM issue

I did my homework, First of all, I found a magnifying glass at work !!!

You are right (as usual ) there are letters on the 2 transistors, on the one on top, I can read "W5", on the bottom one, I think I read "P" or "1P".
Excuse my ignorance but no, I don't know what that mean when there are connections in some pictures and not on others !

I measured the resistance between the red point and pin 11 and it doesn't seems to be connected (1 on the left side of my DMM screen in every range mode)

I also do not find any connections between pins 1 and 3 of the upper transistor, however between the blue dot and pin 11, I found a resistance of 4 ohms.

Using the DMM again, I found a resistance of 4 ohms between pin 1 of the upper transistor and pin 1 of the lower transistor so somehow, there are connected together !

I suspect your DMM leads have an unusually high resistance. Try shorting the probe tips together with the meter on the lowest resistance range and see what reading you get.

That is a peripheral issue, however. I've taken this as far as possible. I have been unable to even tentatively identify either of the transistors. Between the lack of a schematic and the inherent problems identifying semiconductors by their marking codes, I am at a dead end. I THINK the MC33067P has failed, but I can't be sure.

I see two possible approaches. An eBay seller in Malaysia has the MC33067P available for $8 + $6 shipping. Also, several sellers in China have the complete (used) power supplies for $54 with free shipping.

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

I did my homework, First of all, I found a magnifying glass at work !!!

You are right (as usual ) there are letters on the 2 transistors, on the one on top, I can read "W5", on the bottom one, I think I read "P" or "1P".
Excuse my ignorance but no, I don't know what that mean when there are connections in some pictures and not on others !

I measured the resistance between the red point and pin 11 and it doesn't seems to be connected (1 on the left side of my DMM screen in every range mode)

I also do not find any connections between pins 1 and 3 of the upper transistor, however between the blue dot and pin 11, I found a resistance of 4 ohms.

Using the DMM again, I found a resistance of 4 ohms between pin 1 of the upper transistor and pin 1 of the lower transistor so somehow, there are connected together !

[PlainBill]

Re: Samsung 2493 HM issue

First of all, thank you very much for the explanation on the resistors, and the more I look at my 487 ohm resistor, the more I see an 4R7 ! So this one seems to be good !

I measured the resistance between the circled components, I labelled them from the lower left corner 1, then clockwise 2 is the to pin, 3 is the right one.

For the component circled at the top of the picture, I've found:

between pins 1 and 2: 21300 ohms
between pins 1 and 3: 4 ohms
between pins 2 and 3: 21300 ohms

For the component just under the first one

between pins 1 and 2: no reading (1 on the left of my DMM screen)
between pins 1 and 3: 9960 ohms
between pins 2 and 3: no reading (1 on the left of my DMM screen)

Unfortunately I don't see any letter on these components, however I don't have a magnifier :-(

4 Ohms would mean a base-emitter short. That would indicate a problem, unless it's deliberate. More on that later.

I've looked at four pictures; in some of them I swear I can see letters, in others - nothing. I also cannot be sure just what the connections are; in some of them the lower transistor is the only one connected; in others both are. You know what that means, don't you.

Yes, I've marked up the picture again. Pin 11 is marked with a crudely drawn black arrow. There are two areas of interest.

To the right is an area circled in red. At the top of the circle I have placed a red dot on one point. Check if that point is connected (less than 5 ohms) to pin 11. If it is not, ignore that area.

Below pin 11 I have circled an area in blue. Looking at the upper of the two transistors, it appears there might be a connection between pins 1 and 3. Is that real, or is that my imagination? If it's real, we can stop looking. If it was my imagination, we (you) have more work ahead. I've marked the collector of the lower of the two transistors with a blue dot. Is that connected to pin 11? if it is, is there any connection between the two transistors?

Ignore the area circled in white. That was a momentary flight of fancy.

Your profile does not indicate where you are. If you are in the USA, Harbor Freight sells a good magnifying glass for $2.00

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

First of all, thank you very much for the explanation on the resistors, and the more I look at my 487 ohm resistor, the more I see an 4R7 ! So this one seems to be good !

I measured the resistance between the circled components, I labelled them from the lower left corner 1, then clockwise 2 is the to pin, 3 is the right one.

For the component circled at the top of the picture, I've found:

between pins 1 and 2: 21300 ohms
between pins 1 and 3: 4 ohms
between pins 2 and 3: 21300 ohms

For the component just under the first one

between pins 1 and 2: no reading (1 on the left of my DMM screen)
between pins 1 and 3: 9960 ohms
between pins 2 and 3: no reading (1 on the left of my DMM screen)

Unfortunately I don't see any letter on these components, however I don't have a magnifier :-(

[PlainBill]

Re: Samsung 2493 HM issue

Here are some more values with the monitor ON:
Voltage between pins

4 and 1: 5.05v
4 and 2: 5.05v
4 and 3: 2.54v
4 and 5: 5.08v
4 and 6: 0.07v
4 and 7: 0.07v
4 and 8: 5.04v
4 and 9: 14.60v
4 and 10: 0v
4 and 11: 0.19v
4 and 12: 14.06v
4 and 13: 0v
4 and 14: 0.27v
4 and 15: 15.06v
4 and 16: 5.04v

For the resistors, transformer and diode I unplugged the monitor
TM801: 0.8 ohm
Diode DM804: 111.8 ohms
Diode DM808: 111.7 ohms

for the resistor (flat type) can you confirm it's the black one with the value on it ? My DMM read 5 ohms but the value on it seems to be 487 ??

The cap (brown ?) is very small and doesn't seems to be damaged but it's very difficult to say !

Well, the readings on the diodes and transformer make sense. By any chance is the code on the resistor 4R7, not 487?

A quick sidebar. The numbers on one of these resistors are usually vvm. vv represents the value digits, m is the number of zeros that follow the two value digits. A 3.3K resistor would be labeled 332, or 3300 ohms. A 2.2 Megohm resistor would be 225, or 2,200,000 ohms. A resistor labeled 487 would be 480,000,000 - which is a VERY high resistance AND not a standard value.

The standard markings cannot represent a resistance of less than 10 ohms (100), so a slightly different method is used. A 6.8 ohm resistor is labeled 6R8, and a 4.7 ohm is labeled 4R7, which looks a LOT like 487 and measures 4.7 ohms (or 5 ohms).

NOW lets get back to the IC. the voltages you got , and what they mean

4 and 1: 5.05v Oscillator charge
4 and 2: 5.05v Oscillator return
4 and 3: 2.54v Oscillator control current
4 and 5: 5.08v 5.1 V reference
4 and 6: 0.07v Error amp out
4 and 7: 0.07v Error amp - in
4 and 8: 5.04v Error amp + in
4 and 9: 14.60v Enable adj.
4 and 10: 0v Fault input
4 and 11: 0.19v Soft start
4 and 12: 14.06v B output
4 and 13: 0v Gnd
4 and 14: 0.27v A Output
4 and 15: 15.06v Vcc
4 and 16: 5.04v One shot RC

NOW, some voltages seem to indicate problems. From pins 1 and 2 I would suspect the oscillator is not running. Pins 3 and 5 look normal. 6, 7, and 8 also look like part of the circuit is disabled. 9 and 10 look good. 11 does not look reasonable - it should be higher. 12, 13, 14, and 15 look normal, whole 16 looks like it is waiting for something to happen.

Most of these unusual voltage seem to originate inside the IC. The one that stands out is pin 11. The application schematic shows only a cap on that pin, but the power supply has two extra components. I've circled them in orange in the attached picture.

Would you measure the resistance between the pins of these (transistors? diodes?)? For each one, number the pins 1, 2, and 3. Measure the resistance 1 to 2, 1 to 3, and 2 to 3. Also, there seem to be letters on the top of each. What are the letters?

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

Here are some more values with the monitor ON:
Voltage between pins

4 and 1: 5.05v
4 and 2: 5.05v
4 and 3: 2.54v
4 and 5: 5.08v
4 and 6: 0.07v
4 and 7: 0.07v
4 and 8: 5.04v
4 and 9: 14.60v
4 and 10: 0v
4 and 11: 0.19v
4 and 12: 14.06v
4 and 13: 0v
4 and 14: 0.27v
4 and 15: 15.06v
4 and 16: 5.04v

For the resistors, transformer and diode I unplugged the monitor
TM801: 0.8 ohm
Diode DM804: 111.8 ohms
Diode DM808: 111.7 ohms

for the resistor (flat type) can you confirm it's the black one with the value on it ? My DMM read 5 ohms but the value on it seems to be 487 ??

The cap (brown ?) is very small and doesn't seems to be damaged but it's very difficult to say !

[PlainBill]

Re: Samsung 2493 HM issue

Im just wondering something, do you want me to Check all the pins of MC33067P with the capacitor or not ? In the DC or AC range ?
For the diode, to test it for shorts, do I use the multimeter in the diode mode?

Sorry, set your DMM to the 20 Volt DC range; the capacitor will not be necessary.

To check the diodes use the 200 ohms range. It's unlikely the problem is the diodes or the transformer, but check the resistance across both diodes, and across the two pins of TM801.

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

Im just wondering something, do you want me to Check all the pins of MC33067P with the capacitor or not ? In the DC or AC range ?
For the diode, to test it for shorts, do I use the multimeter in the diode mode?

[PlainBill]

Re: Samsung 2493 HM issue

Hello, I'm back !
I didn't find the exact same capacitor but I took a 0.01uF 630V.
Here are the results in AC mode:

Monitor ON

Between pin 13 and 12: 0v AC
Between pin 13 and 14: 0v AC

Monitor Off

Between pin 13 and 12: 0v AC
Between pin 13 and 14: 0v AC

In the beginning, my fingers were in contact with the 2 "branches" of the capacitor and I was reading 25.5v between pin 13 and 12 and 0.7v between pins 13 and 14 with the monitor On and 0v with the monitor Off.
I guess the current was going through my body right ?

Something like that.

Whoops!!! I almost made a huge mistake. Or maybe not.

The data sheet shows pins 12 and 14 connected directly to the driver transformer. For several reasons that is a bad idea, and it would not be possible to have 0 volts and 14 volts at the same time on the two outputs.

This power supply uses a resistor and a capacitor in the drive lines. Also, there may be a problem trying to measure the drive voltage. The typical SMPS runs at 40 - 70 Khz. This is designed to run at 1 Mhz!!! Still, I'm not comfortable with the output voltages you measured earlier. They should have been at some intermediate voltage in my opinion.

First, with the power LED on, measure and report the voltage on every pin of the MC33067P. Use pin 4 as the ground point. I'll examine the data sheet and make sure all of them are reasonable.

Also, I've marked up one of the pictures.

I've circled two components in yellow. These are the resistor and capacitor I mentioned earlier. Measure the resistor, and verify it matches the number on it. Examine the cap carefully for any signs of damage.

I've circled two diodes in blue. these are actually on the top of the board. Check them for shorts. And I've circled the primary of TM801 in white. Check the resistance between those pins.

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

Hello, I'm back !
I didn't find the exact same capacitor but I took a 0.01uF 630V.
Here are the results in AC mode:

Monitor ON

Between pin 13 and 12: 0v AC
Between pin 13 and 14: 0v AC

Monitor Off

Between pin 13 and 12: 0v AC
Between pin 13 and 14: 0v AC

In the beginning, my fingers were in contact with the 2 "branches" of the capacitor and I was reading 25.5v between pin 13 and 12 and 0.7v between pins 13 and 14 with the monitor On and 0v with the monitor Off.
I guess the current was going through my body right ?

[zulururu]

Re: Samsung 2493 HM issue

Thanks for your quick reply ! I'll start by buying the capacitor then

[PlainBill]

Re: Samsung 2493 HM issue

Ok, then I will buy one 0.01uF capacitor tomorrow if possible and retry it again !
How much do you think a ICM801 SMPS controller cost ? Is it cheaper than an analog scope ?

Sorry, my sarcasm (directed at the Fates) doesn't come across properly. Someone in Malaysia is selling them on eBay for $8 + $6 shipping. We aren't quite at that point yet.

A decent analog oscilloscope will run over $100. There are cheap digital scopes that connect to a computer using a USB port, but those present problems. In simple terms, you can't trust their results on a complex waveform. Also, neither can be used to troubleshoot power supplies until you get an isolation transformer.

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

Ok, then I will buy one 0.01uF capacitor tomorrow if possible and retry it again !
How much do you think a ICM801 SMPS controller cost ? Is it cheaper than an analog scope ?

[PlainBill]

Re: Samsung 2493 HM issue

Thank you again PlainBill !

Here is what I have:

Monitor ON

Between pin 13 and 12: 14v DC / 14v AC
Between pin 13 and 14: 0.3v DC / 0.3v AC

Monitor Off

Between pin 13 and 12: 0v DC / 0v AC
Between pin 13 and 14: 0v DC / 0v AC

Those readings indicate the SMPS controller is turning on, but I don't have any idea if the outputs are active or not.

OK, one more thing to try. Insert a .01uF capacitor (Radio Shack Catalog #: 272-131 or similar) between the meter probe and the test points. This will remove the DC component, so simply perform the tests again with the meter on the AC range.

I suspect the SMPS controller isn't producing a drive signal, but it's hard to be sire without an oscilloscope. (What we really need is a $20 200 Mhz analog scope).

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

Thank you again PlainBill !

Here is what I have:

Monitor ON

Between pin 13 and 12: 14v DC / 14v AC
Between pin 13 and 14: 0.3v DC / 0.3v AC

Monitor Off

Between pin 13 and 12: 0v DC / 0v AC
Between pin 13 and 14: 0v DC / 0v AC

[PlainBill]

Re: Samsung 2493 HM issue

Yes, much better. And I've verified that the output of the chip is driving a transformer at low voltage. For the following measurement, use pin 13 as the ground point. If you would, measure the voltage on pins 12 and 14. Do this with both monitor off and monitor on, and try it with the meter on the DC Volts range, then try it with the meter on the AC Volts range.

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

Oops, sorry about that !
This one should be better

[PlainBill]

Re: Samsung 2493 HM issue

Ok, here are the measurements on ICM801:

Monitor switched On

Between pin 4 and 5: 5.08v
Between pin 4 and 9: 14.60v
Between pin 4 and 15: 15.03v

Monitor switched Off

Between pin 4 and 5: 0.01v
Between pin 4 and 9: 0.01v
Between pin 4 and 15: 0.01v

Great picture quality, but has been a failure to communicate. I need a picture that covers the entire bottom of the power supply, just like picture 100_4219 covers the top.

The voltages into ICM801 indicate it should be operating. The voltages you measured are on the input side of the IC, before I have you make measurements of the output side, I want to make sure there are no voltages likely to damage your DMM.

PlainBill

[zulururu]

Re: Samsung 2493 HM issue

Ok, here are the measurements on ICM801:

Monitor switched On

Between pin 4 and 5: 5.08v
Between pin 4 and 9: 14.60v
Between pin 4 and 15: 15.03v

Monitor switched Off

Between pin 4 and 5: 0.01v
Between pin 4 and 9: 0.01v
Between pin 4 and 15: 0.01v