Samsung 245b Plus

[tgu]

Re: Samsung 245b Plus

Blue led on 24.44V, led off -> Decreasing V
Repeating on off hits 24.44V, decrease, 24.44V, decrease ...

I made this table using diode check. MOSFET legs by datasheet goes G,S,D
OL when out of range. No shorts between legs.

Edit:
Inverter was only connected to PSU, not panel with 6 connectors.

[Toasty]

Re: Samsung 245b Plus

MOSFETs look fine.

Transformer checks:

With the 6 lamp connections to the right >>>

Measuring the resistance from pin to pin should match on all 3:

(1)   (5)

(2)   (6)

(3)   (7)

(4)   (8)

Using 200, 20k & 20M scales:

1-2 = 1.2M
1-4 = 2.5M
2-3 = 0
3-4 = 1.2M

5-6 = 1.7k
7-8 = 1.7k

No other readings should be present.

Do you have a bench power supply with current limiting and capable of 24v?

Toast

[tgu]

Re: Samsung 245b Plus

light connector side 1-2 3-4 (?) shows:
1-2 1.7k
2-3 1.7k
Maybe I'm getting it wrong..
other side
5-6 10-20M keeps changing whenever I read resistance
6-7 near 0
7-8 10-20M keeps changing whenever I read resistance
5-8 10-20M keeps changing whenever I read resistance

I don't have own power supply yet, but I could possibly do any needed measurements in school's equipment. That's 1 day delay each time.
I'll make better table of results tomorrow.

[Toasty]

Re: Samsung 245b Plus

No. You got it reversed.

See attached pic.

Try a lower scale instead of 10-20M. That's too high.

[tgu]

Re: Samsung 245b Plus

Not much change..
Applies to all 3 units:

1-2 starting from 12-15M and rising along time
1-4 3.6-3.9M
2-3 ~0
3-4 starting from 12-15M and rising along time

5-6 ~1.7k
7-8 ~1.7k

Using lower range on 1-2 and 3-4 results OL.

[Toasty]

Re: Samsung 245b Plus

Well, I can't imagine all 3 transformers being bad at the same time. The ability to read 1-4 and get ~4M, but not to read 1-2 or 3-4 and get ~2M is odd. Probably attributable to the meter, not the transformers.

At this point I would recommend recapping the PSU complete. Without the ability to apply 24v to the inverter, and because the testing you have done does not point to any failure, that's the path I would follow. It could be nothing more than a small voltage discrepancy on the 24v and the inverter is shutting down because of it. Be aware that the 5.3v is derived from the 24v.

If you need assistance choosing caps for replacements, don't hesitate to ask.
I've used these brands and series in one form or another:
Panasonic - FM, FR, FC
Nichicon - HE, HM

Also see the postings for the 245BW model or the BN44-0195A PSUs.

Toast

[tgu]

Re: Samsung 245b Plus

Need for:
1* 2.2 uF 50v 105C
2* 10 uF 50v 105C
1* 22 uF 50v 105C
3* 47 uF 50v 105C
1* 82 uF 450v 105C
1* 470 uF 35v 105C
1* 1000 uF 10v 105C
2* 1000 uF 35v 105C
1* 2200 uF 10v 105C

If there's someone who's able to find me the 450 V cap, I'd be more than grateful. I think I can find the rest from Farnell.
Current 450 V cap is 25 mm high, lead spacing 10 mm.

[Toasty]

Re: Samsung 245b Plus

FYI - It's a snap-in type cap.

You can slide the capacitance/voltage up a bit on that cap and not have any problems. Might make it easier to find a good fit. e.g., a 100uF@500v.

Forgot the diameter - 30mm

I used a Cornell-Dubilier (CDE) 82@500v

Toast

[barttt]

Re: Samsung 245b Plus

i got a samsung 245b plus from a friend. he said that suddenly the monitor stoped working and than he assembled it. i have no clue what he was doing with it but he gave it to me and if i can repair it it is mine. he does not remember if the blue power light was working or not, but it was not working when i recieved it. when i connected the monitor to my laptop, the laptop could see it is connected to this model.

i have repaired a syncmaster 226bw before by changing some blown capacitors, but in this model i have no clue what is wrong with it. the caps look fine, one is just slightly curved on top. i changed the two resistors that were covered with glue but it did not help.

i have just basic knowledge of repairing this and i would be very thankful if someone has an idea what could be wrong with it.

[barttt]

Re: Samsung 245b Plus

i got a samsung 245b plus from a friend. he said that suddenly the monitor stoped working and than he assembled it. i have no clue what he was doing with it but he gave it to me and if i can repair it it is mine. he does not remember if the blue power light was working or not, but it was not working when i recieved it. when i connected the monitor to my laptop, the laptop could see it is connected to this model.

i have repaired a syncmaster 226bw before by changing some blown capacitors, but in this model i have no clue what is wrong with it. the caps look fine, one is just slightly curved on top. i changed the two resistors that were covered with glue but it did not help.

i have just basic knowledge of repairing this and i would be very thankful if someone has an idea what could be wrong with it.

i am sorry the laptop could NOT se the monitor.