245BW, can't find problem. No 24 or 6.3V, standby is good.

[alexanna]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

The 450v 82uf capacitor has failed on this model,what i have noticed when it fails is a severe flickering of the back lights,But I wonder if it could cause other problems?
Just something to think about.

[PlainBill]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

The 450v 82uf capacitor has failed on this model,what i have noticed when it fails is a severe flickering of the back lights,But I wonder if it could cause other problems?
Just something to think about.

On this particular supply, I don't think that is the issue. It seems unlikely I could overload both outputs and have it work perfectly if the mains filter cap were bad.

PlainBill

[Toasty]

Samsung 245BW - No 24v or 5.3v - standby is good

**UPDATE**

I have received this unit (purchased) from epicelite.

I recapped the PSU to my specs for caps using HE, FM, FC series'. It eliminates questions down the road. Since there has never been a list made of the originals I was unsure of what was in place when I got this unit.

I did some Googling and came up with:
http://www.ccl-la.com/blog/index.php...4-lcd-monitor/

It is not the same monitor { 2493HM }, but it is the same PSU, BN44-00195A. A list of caps is provided, but the page is done as a graphic so the list and repairs can't be copied (easily). { Hello PaintShop camera mode! }

{ Elektrotanya skips right over this model number in it's BN44- series listing. }

After recapping, a bench test showed the supply in correct working order as PlainBill had noted when he had it and tested it. BTW: It's 5.3v, not 6.3v as the thread title indicates.

Reassembled the unit and the symptoms remain. Went to check the inverter and saw no 24v available. The meter would flicker occasionally on pressing the power button, but no significant reading, except that -something- was happening.

Disconnected the interconnect cable to the Graphics board. Cycled the power and 24v came right up and stayed on the Graphics board connector.

Shut the unit down and started probing the inverter board with the ohmmeter.
Found both lower FETs shorted on the board. One D-S, the other G-S.
An ohms test of the 3 transformers show them to be a match.

Both FETS are from Anpec and listed as Enhancement Mode types.
APM4030A - N Channel
APM4050A - P Channel

Not available anywhere in the US, but Anpec's site shows them as in current production.
A suitable replacement could likely be found by datasheet-to-datasheet comparison, but I became bleary-eyed after the 6th sheet and went browsing.

Found a salvaged inverter for cheap from a different model monitor { LS24HUBCFL }, but again, the board is the correct number, BN44-00163B.

I figure that either I will get a working inverter or at the least the 2 FETs I need to finish this one.

The question remains: What caused the FETs to blow in the first place?
Both inverter onboard caps test good in ESR, value, leakage.
The fuse is intact and the board shows no darkening from overheating.



Toast

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Caps List for BN44-0195A power supply Samsung 245BW :

MAXIMUM HEIGHT = 25mm

There is sufficient room around the caps that a 12.5mm can be used where a 10mm was, or a 10mm for a 8mm, etc.

Mains (original to board) cap was not replaced. Tested good in ESR, value, leakage.

CB804 - 22 / 50
CB805 - 2.2 / 50
CB806 - 47 / 50
CB809 - 47 / 50
CB812 - 47 / 50
CB853 - 2200 / 10

CM814 - 10 / 50
CM851 - 1000 / 35
CM852 - 1000 / 35
CM855 - 470 / 35
CM857 - 1000 / 10

CP801S - 82 / 450 { ~30mm diameter, 20mm height }
CP804 - 10 / 50

13 caps

I'll get some drawings and photos up when I can.

Toast

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

** UPDATE **

Inverter board was received and installed. Unit now works very nicely.

Awaiting some caps to redo the Video/Graphics board as kc8adu pointed out issues with the 225BW he has.
I investigated mine and found some widely varying ESR readings on identical caps... 'nuff said!

See Page 24 of this thread:

https://www.badcaps.net/forum/showth...t=6930&page=24

.

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Hello

I know this is old topic but I've got very similar issue with exacly the same power board and I'll need your help.
Blue led is solid, I can power on/off. I have no 5.3V and 24V.
What I've done so far:
- I recaped all electrolytic capacitors - Rubycon ZL, YXF, Panasonic FR (are they no good?) and FR and large Chemi-Con KXG (good enough?)
- I changed two shorting transistors: QM802 and QM803
- I removed yellow glue

I measured voltage on ICM801:
Pin 4 as ground
1 - 4.27V
2 - 4.27V
3 - 2.66V
5 - 5.10V
6 - 3.21V
7 - 3.21V
8 - 5.08V
9 - 14.55V
10 – 0.2V
11 - 4.98V
12 - 6.88V
13 - 0.00V
14 - 7.08V
15 - 14.98V
16 - 2.58V

ICB801S
Pin 3 as ground
1 - 24mV
2 - 16.50V
4 - 1.21V
5 - 390V

And few more:
5.3V - 0.47V
24V - 48mV
Standby – 5.29V
PSON – 3.25V

Big Cap – On – 390V Off – 330V

What would be my next step?

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Sorry first listed Panasonic is EB (are they no good?).

[selldoor]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

So have you checked out the inverter board as per toasty

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Yes. Non of the FETs are shorting.
U5 - 4.73K
U3 - 10K
U4 - 10K
U6 - 4.71K
Fuse F1 not blown

[selldoor]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

So - if you unplug the inverter board does the 24v come up on the power supply?

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

No, only 35mV. But when I keep the probes on it's going slowly up to about 47mV.

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Check the long blue cap as in post #46.

Check the power resistors in the drains(?) of QM802/803. One mounted horizontal next to long blue cap and one vertical.

Make sure you are measuring from ground on the correct side for the 5.3v & 24v. Once you cross the fat white line and cuts in the board you are on a different circuit.

On the foil side, check the SMD components on the COLD side between the large transformer and the connector for the 5.3v standby. This would be near the optoisolators. (See attached pic.) I have found SMD resistors burned and a transistor there also. Use some good light and magnification to carefully inspect (jeweler's loupe).

A clear, well lit photo of that area would help.

If you follow the 24v circuit from above the transformer to the connector/area for the 5.3 & SB voltage, there is a wire jumper that you can lift one side of and see if the 24v comes up. ( J830 ? ) If it does, the fault is in the section near the opto's, as I mentioned.

There is a "balance" circuit used here that looks at the 24v & 5.3v. (2 zener's and a dual diode) If either one goes too far out of spec (high or low) it causes one of the opto's to send a signal to the shutdown pin on IC801S.

T

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Both QM802/803 are brand new.
I haven't got correct value to replace 12nF blue cap. Closest value I've got is Wima MKP 100nF 400V. This is almost impossible to buy in the UK. Only Farnel has it but minimum order of £20 apply :/
All SMD transistors and resistors in the section you mentioned seems to be ok. I will attach pic in few minutes.
One more I think important information. The input voltage on the large transformer is 0V.

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

A picture you asked for

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

RT852 looks blown. Same appearance as in my pic above. IIRC it's a 100Ω.

T

[Toasty]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

<<Both QM802/803 are brand new.>>

I know that. I'm saying check the power resistors right in front of them. Usually they go when one or the other FETs blow. Current limiters (fusible resistors).

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Oh yes, the power resistor is blown. That was the very first component I checked but I can swear it was good. Strange... ok I'll replace it and I'll report.
Oh yes RT852 shows 168R.

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Closest value I'got at home is 1.4R 5W. Do you think it would be ok just for tests?

[selldoor]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

@Toasty If he needed to rplace the Long Blue cap could he use one of these?
http://www.ebay.co.uk/itm/PANASONIC-...=e100084.m1843

[Yaaman]

Re: 245BW, can't find problem. No 24 or 6.3V, standby is good.

Good shot. I didn't find it because it is not in caps category. Thanks.
Hopefully I won't need it and the new RT852 will sort it out.