Samsung Syncmaster 245BW

[dbinokc]

@Toasty,
I did some more checking last night. I rechecked the other two 68 ohm resistors to make sure thay had not opened up after my replacing the first one. They were still good.
I was doing some probing and accidentally hit the hot hotsink with the grounded portion of scope probe. Should have setup that isolation transformer after all! Before I can continue, I will need to get a replacement fuse.
I did not get a chance to try your disconnection suggestion before I blew the fuse.

[Toasty]

Silicone sealant/caulk is perfect for these. Use a 100% silicone type.

The noise can also come from a poorly wound transformer or the coils nearby. But, that is usually more of a buzzing sound than the ticking/clicking as you describe.

[dbinokc]

I got my replacement fuses. I did the video card test. I removed the connectors from the video card side. When I probed the 24V I saw a 160V pk-pk AC waveform at the 24V. With the card connected, this went to 0V.
I need to figure out where I can get a ground reference on this board. I find it hard to believe I have a real 160VAC running around on 24V.

Just as a later edit, I have my isolation transformer connected to the monitor now. I just need to find a good place to attach my ground lead, so I can get rid of AC showing up all over.
I can't really flip the board over over. If worst comes to worst I can solder a wire onto the minus of the bridge and run that out.

[Toasty]

Where are you attaching the ground lead? Is the meter set to DC?

Minus (-) of the bridge is only to be used for HOT side measurements.

Ground on the output side -should- be the chassis.

You can also measure directly across the output side of the video card as 5 pins are +24v and 5 are ground feeding the inverter. See the markings on the inverter board.

Toast

[dbinokc]

I am probing with my oscilloscope, not a multimeter. I have been grounding to the chassis, but I was planning to ground to the negative side of the bridge since I have the isolation transformer setup on the monitor.
I just need to find a place to connect. I can not really flip the board over while the power is on because of the cables. If I can not find a good place to connect to on the top side, I will solder a wire on the bottom side and and get to the hotside ground that way.

[jetadm123]

The negative side of the bridge rectifier is also connected to the negative lead of the large 450V cap.

[Toasty]

You can't get rid of the AC. It's induced by the switchers and transformers.

Just use a DMM.

Connect everything, and pull the video card plug. Push the power button and see if the +24v comes up.

The metal frame/chassis -is- the ground.

[Toasty]

Where the hell did my post go from last night with the pictures?

Let's try this again....................

Note that HOT side -Ground- and Cold side -Ground- are connected thru the screws for the PSU board.

Negative on the HOT side may be Ground for those circuits, but should not be confused with chassis Ground.

Denoted in schematics differently.

.

[dbinokc]

Hooked up my isolation transformer and a ground off the negative side CP803.
I finally have some voltages that make a little more sense now. I am seeing 180VDC off of DB801 on both sides.
I removed the cables from the video side and checked for 24V. I found no 24V. I also checked FB802S and it was not open.

I probed VCC of ICB801S and found about 15V.
I probed VCC of the F92222L and found 0 volts. I also probed off of the
68ohm resistors and found no voltage present there as well.

It looks like things are leading toward maybe QB801 or maybe DB803.

Will do more checking tomorrow.

[dbinokc]

The monitor is working now. It turned out to be that RB803 was open as well. So that is two bad resistors on this monitor. I replaced with a 2.2 ohm and it works. Now I just have to put it back together.

Since RB803 and the 68 ohm resistors both have that coating on the leads, I have to wonder if it is causing some kind of corrosion that is causing the opens.

I appreciate everyones patience with my bumbling around some. I normally build electronic projects, not try to fix them. I only bothered trying to fix this time, because it is part of a triple monitor setup and they do not sell 245BW's anymore.

Big thanks to whoever did the schematics.

[Prismatic]

I replaced all the caps on my flickering 245BW power supply as well as the infamous trio resistors. Yet the flickering continues just the same, no improvement.

There are four 220uF caps on the inverter. Should I replace those as well? I haven't seen any discussion on the inverter caps and flickering problem. Everybody has had so much success replacing the caps on the power supply I fear this will not help me... Any thoughts?

[Toasty]

I would replace them first. Sounds like you have the BN44-00149A inverter.

Since you are new, (1) Welcome! and (2) what/whose caps did you use for the power supply?

Can you get to the service menu and see how many "On" hours it has?

-Could- be the tubes.

With a signal applied, adjust Brightness and Contrast to zero (0), then press the ENTER button for more than 5 seconds. The menu should appear. Make a note then cycle the power to exit.

Toast

[alexanna]

Originally Posted by Prismatic

I replaced all the caps on my flickering 245BW power supply as well as the infamous trio resistors. Yet the flickering continues just the same, no improvement.

Check the 82Uf 450 volt capacitor

[Prismatic]

First of all Toast, thank you for the warm welcome!

I accessed the service menu. The on time is 32 hours. Doesn't seem like that much... I replaced the capacitors with NTE's from Frye's (including the 82uF 450V). I will have to return to Frye's to pick up the 220uFs for the inverter board to give that a shot. I don't know how to check caps with my multimeter (if its even possible).

Also I would like to note two more characteristics of the flickering symptom: (1) the flickering begins at a rate 5 -10 times second when I first turn it on, but then almost goes away after an hour of being on; (2) when following your instructions to access the service menu I notice that the flickering just about went away completely when the brightness was on zero. As I dialed it back up I found at around 40 the flickering began to come back (maybe 1 flicker per 10 seconds). Not sure if that helps decipher the cause or rules anything out.

[PlainBill]

Originally Posted by Prismatic

First of all Toast, thank you for the warm welcome!

I accessed the service menu. The on time is 32 hours. Doesn't seem like that much... I replaced the capacitors with NTE's from Frye's (including the 82uF 450V). I will have to return to Frye's to pick up the 220uFs for the inverter board to give that a shot. I don't know how to check caps with my multimeter (if its even possible).

Also I would like to note two more characteristics of the flickering symptom: (1) the flickering begins at a rate 5 -10 times second when I first turn it on, but then almost goes away after an hour of being on; (2) when following your instructions to access the service menu I notice that the flickering just about went away completely when the brightness was on zero. As I dialed it back up I found at around 40 the flickering began to come back (maybe 1 flicker per 10 seconds). Not sure if that helps decipher the cause or rules anything out.

That's the problem right there. A SMPS requires low ESR caps to operate properly; NTE doesn't carry low ESR caps. The usual suggestion is to order Panasonic FM or FR series caps from DigiKey. Specify USPS First Class Mail for shipping and they will be in your hands in two days.

PlainBill

[Prismatic]

Wow. Alright, I'll give it a try! Thank you PlainBill

[Prismatic]

Originally Posted by Prismatic

Wow. Alright, I'll give it a try! Thank you PlainBill

Would you suggest buying this kit:

http://lcdalternatives.auctivacommer...-P2070088.aspx

And then adding the 82uF 450V (which he explains why he excludes it from Kit)?

Or just itemize them all on Digikey and go that route?

[Toasty]

Ditto, PlainBill's response. I -just- repaired one here from a member that used them. Not acceptable capacitors except for the 82uF. Your original cap is probably okay.

[PlainBill]

Originally Posted by Prismatic

Would you suggest buying this kit:

http://lcdalternatives.auctivacommer...-P2070088.aspx

And then adding the 82uF 450V (which he explains why he excludes it from Kit)?

Or just itemize them all on Digikey and go that route?

Make a list with the critical parameters - Capacity, voltage, diameter, and maximum height. Go on Digikey and search on the parameters capacity, voltage, and FR (for an 820µF, 25 volt cap you would enter 820uf 25v FR), set the 'In Stock' box on, then search. Then make sure any hits match the diameter and height restrictions. If there are no hits, change the FR to FM, and search again. Repeat for all capacitors. Since they won't ship until Monday anyway, post your list of selections here and someone will verify it.

PlainBill

[Prismatic]

CM851 & CM852: 1000uF 35v (found FR)
CB876 & CB809: 1000uF 10v (found FR)
CM809: 100uF 50v (found FR)
CB872: 22uF 50v (found FR)
CM863: 470uF 35v (found FR)
CM862: 1800uF 16v (found FR)
CM813: 10uF 50v (could not find FR or FM)
CB810: 1uF 50v (could not find FR or FM)
CB806: 68uF 63v (could not find FR or FM)
CM810 & CP808 & CP811: 47uF 50v (could not find FR or FM)

Digi-Key
Qty Part No. Description
1 P14452-ND CAP ALUM 22UF 50V 20% RADIAL
1 P14454-ND CAP ALUM 100UF 50V 20% RADIAL
1 P14441-ND CAP ALUM 470UF 35V 20% RADIAL
2 P14378-ND CAP ALUM 1000UF 10V 20% RADIAL
2 P14445-ND CAP ALUM 1000UF 35V 20% RADIAL
1 P14401-ND CAP ALUM 1800UF 16V 20% RADIAL
Subtotal $5.71

The part numbers are linkable. I got this monitor from someone who gave up on it, I hope he didn't replace any of the caps with different caps before I got it - causing me to try to replace a wrong cap with a new wrong cap...

Thanks for your help guys! Not sure what to do about the caps I couldn't find FR or FM.