samsung UN46c5000QF

[martino]

Re: samsung UN46c5000QF

So,played some more with the PSU.
Even when I just jumper ps-on with stb,the backlight flashes on and off for approx 10/15 times...
So,I'm thinking I got a PSU problem.It does have all voltages (12,5 etc) but those also flash on and off in sequence with the backlight.
I assume the PSU should just stay on with 16/18 jumped? Any ideas??

[martino]

Re: samsung UN46c5000QF

I measured the bridge rectifier.
On the DC side I get :107 volts DC for a sec,then it starts jumping between 160 and 100 volts,till the backlight stops flashing,then it stays at 137 volts.
On the AC side I get : 120 volts AC steady

I assume the voltage hobble on the DC side gets caused by the backlight current as it's switched on/off?

Can I unplug CNL801 (plug that goes to backlight) and turn on the PSU? Or is that gonna wreck something(as in it needs a ballast load?)

[tom66]

Re: samsung UN46c5000QF

You can try without backlight on these sets.

[martino]

Re: samsung UN46c5000QF

Ok,thanks for the quick reply.
So I unplugged the backlight connector,and the PSU is still doing the same thing,voltages all jump up and down from their value to zero,for like 10 sec,then it stops and everything is dead.
That eliminates the backlight as the problem I take it

Now it gets interesting,lol
You think the PSU is "seeing" a fault and therefore shuts itself down? (tries to turn on several times before it gives up,hence the flashing?)
Looking on the scematics,it seems to me that ICB801 is in "charge" of the on switching of the power supply?

[tom66]

Re: samsung UN46c5000QF

Do you see a PS ON pin? Is that fluctuating?

[martino]

Re: samsung UN46c5000QF

Now the easy way out would be to just buy a different PSU.
But I'm in no hurry and wanna learn as I go,so I decided to try and fix this PSU on component level.

Now before I'm trying to fix a perfectly good PSY board,I have a question:
I'm "forcing" the PSU on by jumping a 1K resistor from STBY to PS-ON.
On the same connector CNM801 there is also things like:Vamp,H-SYNC and P-dim.
If the PSU doesn't see input on those,would it still turn on or do I need to jumper those too??

[martino]

Re: samsung UN46c5000QF

Do you see a PS ON pin? Is that fluctuating?

I unplugged the mainboard and put a jumper on PS-ON via STBY.

[tom66]

Re: samsung UN46c5000QF

OK. So, check the voltage across the 450V capacitors. Stable or unstable? For now, ignore bridge voltages.

[martino]

Re: samsung UN46c5000QF

The 2 large caps CP804 and CP805 show:
standby: 167 volt stable
ps jumped: 387 volt DC stable.also,they remain showing 387 after the fluctuation is finish.
CP806 shows:
standby:167 volts dc stable
ps jumped:fluctuates between 124 and 135 volts,after fluctuation it stays at 135 volts stable.
CM813 shows:
standby :0 volts
ps jumped :first jump up is 866 volts then fluctuates between 0 and 177 volts,after fluctuation it drops back to 0 volts

When I jumper the PSU on it takes about 2 seconds before it starts fluctuating,then it fluctuates for about 10 to 15 seconds before it stops..

[tom66]

Re: samsung UN46c5000QF

What is the capacitance of CP806? It might be bad.

[martino]

Re: samsung UN46c5000QF

on schematic it says its a 1000nf minimum 400volt
I tested it with my volt meter but not sure if this is how its done (see pic) I don't have a ESP meter
My meter on 2uf setting(200nf setting says OL) says it's 0.961 .
I assume that's 961nf...

excuse the filth on my meter,it get's used on automotive daily...lol

[tom66]

Re: samsung UN46c5000QF

That is expected for such a capacitor. In standby it has 165V mostly, but when operating it has 0~165V full-wave rectified sine (PFC decoupling capacitor) which averages to approx 165V/sqrt(2) = 116V.

[martino]

Re: samsung UN46c5000QF

That is expected for such a capacitor. In standby it has 165V mostly, but when operating it has 0~165V full-wave rectified sine (PFC decoupling capacitor) which averages to approx 165V/sqrt(2) = 116V.

So, we can conclude that cp806 is good?

[tom66]

Re: samsung UN46c5000QF

Yes.

[martino]

Re: samsung UN46c5000QF

poking around in this PSU trying to trace voltage.

When I measure pin 5 off TB801(one lead on the negative from rectifier,other on pin 5) it goes up beyond my MM(1000 volt DC). When I look at the schematic it says 60T at pin 5,that means 60 volts?

[martino]

Re: samsung UN46c5000QF

disregard the last post,lol

I'm concentrating on the smtp chip now,ICE3BR1765J. it's ICB801 on the PSU
Reading up on it's function I thought it would be a good thing to check.
But,was in the process of measuring the VCC and drain,when my MM lead slipped and now it's a fact I have to replace it cause I blew it right off the board,lol
Will report back when I got the new one in

[martino]

Re: samsung UN46c5000QF

Final report: TV is up and running...!!!!!!!!!

I ended up just replacing the PSU when I found one for $29.95 on ebay
For that price I couldnt let it go,set fired right up...

Now I got curious,it had the newly bought main board in it when I fired it up,so I swapped it out for the original main board and TV didn't work.

So end conclusion is that this TV had both the main and power boards broken.!
I'm guessing one took the other one with it when it died...

Thanks again for all the wonderful help from all the skilled people on this forum,you guy's rock

[martino]

Re: samsung UN46c5000QF

One more question:
I remember tom66 saying in a post "and that's why it's always a good idea to reset the mainboard cause..............."
Can't remember the reasoning behind it but when I read it,it made a lot of sense,could you refresh my memory on why it's good to do a reset on a bought mainboard??