Samsung 191T

[zandrax]

I bought an used Samsung 191T: it's a 19" with one of first Samsung PVA panel, manifactured in late 2002. This is the model with the embedded psu (there was one with an external 14 V brick) and pivot capabilities.
Following Wizard's avice, I opened it looking for badcaps:

Rear plate:


From left to right: inverter, power and logic boards:


The logic board, based on the Genesis GM5020: most caps are Samyoung polys (or fake polys, who knows?), the two lytics near the Genesis are two Samsung FX 47 uF 6.3 V. Noone bulging.


Power supply board: full of CapXons but surprisingly noone bulging again. The primary cap is a CapXon KF (can't read any marks, I suppose a 470 uF 400 V cap), the ones in the upper left corner are KMs (5 1000 uF 10 V and one 470 uF 25 V), below the main thansformer there are two small KMs and, hidden by the right heatsink, the last small KM. All caps are manifactured between 44th and 48th week of 2002: are they still inside the bad electrolyte manifacturing period or not?


The inverter board with only a cap: of course it's the bulging one!
The insulating paper is burnt: the inverter must run hot, no wonder the cap is failing.


Can't read any brand, but it's a 220 uF 25 V cap with green jacket and gold writings; the vent is a three-pointed star with a small marks between each two radius: according to capacitor.web it should be a Teapo or a Tayeh, more likely to be a Teapo. What a luck!


Any idea about a replacement for the bulging cap? Apparently the backlight has not an issue, but I would replace the c[r]ap before having to replace the whole inverter board.

Zandrax

[Wizard]

Check them with ESR if you can or simply replace big caps on the PSU and lamp inverter.

Resolder the PSU too. I had few that had this solder issues on the PSU where the stand up transistor cut the power to the inverter.

The SMD electrolytics on the mainboard do go high in ESR when it get old. That is what I don't like about at all. Doesn't swell up at all basically "silent death".

Cheers, Wizard

[zandrax]

Thanks Wizard.
I have to buy an ESR meter to check those nasty caps, both the CapXons in the psu (if they're within spec, is it safe to keep them?) and the (most likely) fake polys in the mainboard.
Should I replace the Teapo with an high endurance (e.g. Panasonic NHG) or Low ESR (Pana FM) cap? I think a low ESR one, but better feeling safe than sorry.

Zandrax

[Wizard]

Wait. Get your ESR meter first then we'll discuss.

I just reworked my 191N LCD. Bad caps in there.

191T and 191N is similar except yours is much OLDER version of 191T. My 191N have DVI circuits but not installed and is 2 board design & one IC (newer).

Cheers, Wizard

[Scenic]

hmmm.. that PSU board looks almost exactly like the one in my Samsung 151BM (15")
except mine doesn't have a power switch and the connector for it..
(and it has this dumb butterfly-style power cord connector -.-)



http://www.badcaps.net/forum/showthread.php?t=6065

replaced the primary side crapXon with a NCC KMG 400V 100µF and all secondary crapXons with Sanyo WG 16V 1500µF (they weren't bulging but.. well.. they were crapXons )

[kc8adu]

replace the bulger and all on the power supply.
panasonic fc are fine.
resolder the mosfet thats not on a heatsink and the 2 rectifiers on the heatsink.

[Wizard]

Also the one or two SMD capacitors near the LVDS cable (this one with very thin wires) for the LCD. I always find htem bad.

Cheers, Wizard

[zandrax]

@ Wizard:
You're speaking of a year 2003 191N: contemporary 191T was a 191N with both DVI and VGA connectors; from late '03 there was even the 191T Plus with same panel and improved contrast ratio (brighter CCFLs?).
Is the LVDS cap a cap to resolder or to replace?

@ Scenic:
I agree, the power board is almost identical.
I looked for CapXon KF datasheet: KF it's a Low ESR series, quite strange to see it employed as a primary cap. Maybe this is the reason why others aren't bulged yet.
Moreover the KF has, according to CapXon datasheet, a capacity of 47 uF or smaller, not the 470 uF I supposed.

@ KC8:
Thanks for suggestions: so CapXon is a no-no brand whetever they are bulged or not.

I'll update the thread after the recapping: this will take some time since I'm busy until late february.
Thanks to everyone again.

Zandrax

[willawake]

pva will be nice. i like samsung pva

[zandrax]

Originally Posted by willawake

pva will be nice. i like samsung pva

I agree: colors on TNs are washed, MVAs and PVAs show them strong.
BTW this is among the first PVA panels manifactured by Samsung so you get a slow response time by today standard (25 ms: anyway good enough for watching movies) and some image retentions (a temporary "burn in" effect: after 5 or 6 hours I see the taskbar. Lessened by automatically hiding the taskbar and switching to a solid white desktop background).

Zandrax

[Wizard]

Replace with low ESR electrolytic (legs bent out and trimmed to sit on the pads). I simply grab the top of can and, gently pushing down, rotate can like doorknob back and forth to break off the legs on the SMD electrolytic and flick off remains off the pads.

Actually my 191N is 2004, later one. Your is much older due to 3 boards, many chip count etc. Note again: mine is 1 IP board (inverter and power on one board) and other board only have one big chip, no ram at all with few other SMD devices with DVI circuits present but not installed.

Cheers, Wizard

[Wizard]

Update:

This is pic of 191N, you can see circuit and only 2 chips (one is main for signal conversion from either DVI if used or VGA singal to LVDS signal for LCD), one square chip in socket is microcontroller.

No ram at all as you can see and much less complex. Note I had to remove the shielding on the LCD data bus board with DC-DC converter to trace the power traces so I can circle the vias and screw it back on without shield and measured voltages while it's running, hence the reason for cardboard under the mainboard. And voltage written on besides each circled vias. This is not a reference but this is to give you idea how I document a unknown LCD circuitry.
IP board already have clear plastic shield.



Cheers, Wizard

[zandrax]

Thanks Wizard: your monitor is different from mine, the power board isn't filled with all caps so it must be shared with bigger Samsung screens (say 21-22" of the time). The labeled chip is the bios so your is a single chip design as mine (the controller handles both DVI/VGA input and LVDS output), simply is more recent: your should have the Magic Bright command (- button) for brightness presets.

Zandrax

[Wizard]

Yes, have the magicbright button as well.

It was useful feature to draw out the dimming CRT monitor samsung I had. I had to use it to light up the dim CRT more in final 9 months of it's 4 years life. Prior to it, I never used the magicbright feature and probably never will. I do have this as well on my 19" LCD also, untouched.

I have done lot of research and there are chart on the service samsung (it is internal document that only authorized samsung servicers can access to) that board will only drive up to 17" to 19". 22"-24" has 2 extra lamps, sometimes three more.

Reason I did lot of this inverter board research was so I can order a suitable substitute and which I did twice to fix 2 non-samsung monitors and works well that they had blown transmformer necessites whole inverter lamp board replacement.

Cheers, Wizard

[MIRJAN1531]

Can any one help me with the IC power "part number" because i lost it ...
Thank you

[MIRJAN1531]

I will pay pleaseeee .... Can anyone help me .

[retiredcaps]

Originally Posted by MIRJAN1531

I will pay pleaseeee .... Can anyone help me .

We have NO IDEA what you are talking about re the IC power part number. A picture or description will help.

[MIRJAN1531]

During the repairing i have lost the Power IC (5Pins). The Power IC must have a "Number" I need it to buy another one but i cant find it on datasheet without the number.

Thanks alot...

[Scenic]

mine says:
S0152
C
DP502T



http://www.badcaps.net/forum/showpos...93&postcount=3

[MIRJAN1531]

thank you ................. this is the best site .... thank you scenic you are the best.