Samsung 275T Plus (PS: BN44-00163A)

[ckrtech]

Hey all -

This forum appears to be a great resource for my current project. I have done a lot of recapping on old video game systems, but I haven't tackled a power supply board or boards with voltages over 12.

Here we have the PS board for a Samsung 27" monitor from circa 2008. After a bit of flashing on first power-up occasionally over the past few years, it finally started requiring the main switch to be flipped at the AC input in order to get a picture just this past week. Even then, it would sometimes only show an image for a few seconds before powering down and cycling. Switching on and off a few more times could finally bring it back to life (until next power down). Now...it doesn't really want to power on. Smells like bad caps to me.

I have found a few threads here and there for the monitor board I am working on, and I thought I would describe my project/issue, post some pics, and also ask a couple of questions. Maybe this thread will help add to the Google results for anyone else in the future.

Questions first -

1: I have never actively discharged a large capacitor on a PCB. Do you guys tend to use a bleeder resistor for this sort of thing? I don't have any (yet). I imagine the only thing I need to worry about is the 450V 150uf, but I will differ to your other possible safety recommendations.

2: I have concerns about this... glue? (See pictures)

Plan is to replace all caps except the 450V unless additional suggestions/points are made. I can also add any pics if requested. Thanks!

[budm]

Re: Samsung 275T Plus (PS: BN44-00163A)

You also need to remove ALL the glue, otherwise:
https://www.badcaps.net/forum/showth...ight=BAD+GLUES

[ckrtech]

Re: Samsung 275T Plus (PS: BN44-00163A)

OK. Looks like near the end of that thread you mentioned just using alcohol to soften things up a bit?

I guess I'll also pick up some electronics grade silicone. Maybe... http://www.amazon.com/MG-Chemicals-C...ronic+silicone Stuff seems maybe a bit expensive but is Prime eligible.

[budm]

Re: Samsung 275T Plus (PS: BN44-00163A)

No need to reapply the glue. Glue is used to hold parts in place during wave soldering.

[ckrtech]

Re: Samsung 275T Plus (PS: BN44-00163A)

No need to reapply the glue. Glue is used to hold parts in place during wave soldering.

Ahh OK. I thought it was a vibration protection type of thing as there are a few transformers on this board. Thanks. Makes it easier! ...so long as I can get the glue off.

[Lumberjack777]

Re: Samsung 275T Plus (PS: BN44-00163A)

Nice pictures. In your first picture you can see the 2 on the left are definitely bulged. So cap replacement will most likely fix this monitor. As far as the glue goes... You don't have to remove every little bit, from every component. Think of it as a conductor. You just need to remove the glue where it can be conductive and cause a short.

[ckrtech]

Re: Samsung 275T Plus (PS: BN44-00163A)

Nice pictures. In your first picture you can see the 2 on the left are definitely bulged. So cap replacement will most likely fix this monitor.

Yeah! I was glad I opened the monitor as soon as I saw those two guys.

As far as the glue goes... You don't have to remove every little bit, from every component. Think of it as a conductor. You just need to remove the glue where it can be conductive and cause a short.

Yesterday I removed all caps except the three that are glued. I attempted to soften the glue a bit but didn't have success. I haven't attempted it yet today. Any removal suggestions/techniques? No luck with the alcohol application (only worked on the one in the second picture).

[Timo_K]

Re: Samsung 275T Plus (PS: BN44-00163A)

ckrtech:

You can use a sharp scalpel blade and tweasers to remove the glue.

Anyone that can offer any help with my following question?

I need to make sure that also the 2 fuses on that Power Supply board need replacement after encountering exactly the same problem with the glue thing, on this type of screen.

6.3 Ampères they both are.

Anyone that can offer any help in this last question please?

[budm]

Re: Samsung 275T Plus (PS: BN44-00163A)

ckrtech:

You can use a sharp scalpel blade and tweasers to remove the glue.

Anyone that can offer any help with my following question?

I need to make sure that also the 2 fuses on that Power Supply board need replacement after encountering exactly the same problem with the glue thing, on this type of screen.

6.3 Ampères they both are.

Anyone that can offer any help in this last question please?

Are you talking about the two white fuses (one for line, another one for Neutral) for the main AC input?
BTW, I also need he straight shot pictures of the board top side and Bottom side, shopjimmy does not have the pictures of this BN44-00163A for me to look at.

[Timo_K]

Re: Samsung 275T Plus (PS: BN44-00163A)

Exactly.

The two white fuses for main AC input is what I am talking about.

I am going to ask a friend of mine to take a straight top side and bottom side picture for you tomorrow because my own camera is far to low quality to make it look clear and detailed.

[budm]

Re: Samsung 275T Plus (PS: BN44-00163A)

They are time-delayed (T) fuse, if they are blown then you probably have either shorted out bridge rectifier, or shorted out PFC Power MOSFET for the PFC Voltage booster circuit.

[Timo_K]

Re: Samsung 275T Plus (PS: BN44-00163A)

So the fuses don't appear to be blown.

I also took 2 pictures that hopefully are clear enough.

You can still see some glue remaining here en there, but most of it is gone now.