samsung ln52a750r1fxza red light blinks

[LITEZONER]

i read all the threads on these sets, I have 5V standby at PS, no other voltages are present, all it does is red led in front blinks very slowly, PS caps LOOK good no bulging or leaking, but i am wondering if all those little caps on the back of the main board could be the culprit? seems the main turns on the ps on these units Thanks

[Andrew F. Ali]

Re: samsung ln52a750r1fxza red light blinks

The little caps on the Main Bd don't usually go bad...not saying they don't, though....but do you know how to Self-test the power Bd?

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

I sure don't know about a self testing procedure or anything like that, is there some sort of flow chart? thanks for the reply.

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

Okay so just poking around here, Pushing down on cn801 the connector that plugs into the power board BN-44-00201A, I get a relay click and the source light flashing

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

Plugged the LVDS cable back in, forgot it was unplugged...... and source light does not flash anymore, just the standby light flashes a couple of times then goes out, Looks like i need to re work some solder joints on the PS board? for further testing

[Andrew F. Ali]

Re: samsung ln52a750r1fxza red light blinks

Could we see clear pics of the Pwr Bd, please...especially the connector that goes to the Main Bd. i.e. to determine which pins are Stby 5V and etc?

[CapLeaker]

Re: samsung ln52a750r1fxza red light blinks

Post a high res, straight shot picture of the back of the main board.

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

so i get the 5.1V on pin 3 no other voltage is present, i have not tried holding down the spot that makes the relay click and measure the voltages, included is a picture of the back of the main board as well. Thank you

[CapLeaker]

Re: samsung ln52a750r1fxza red light blinks

try to turn the TV on and measure the DC V on all the pins on the PSU connectors CN801 and CN803.

Post the pin out name with the voltage measured.

You may want to check the tantalum caps on the back of the main board as well.

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

Okay so here is what i found so far, based on the relay clicking in i was led to think of a cracked solder joint or loose one, re worked a few suspicious welds, found big blob of solder crossing the pins in the picture, got out my wick and cleaned it up, Put board back in, blew fuse. URG! so back to the bench under magnification, i noticed a jumper that I think is suppose to be there but it was missing, so i checked over all the welds on the cold side and soldered in a Jumper in that position in the picture, Put board back in Blew Fuse. URG! Again.

[CapLeaker]

Re: samsung ln52a750r1fxza red light blinks

if the fuse blows instantly, you got something shorted on the primary.
I see you circled something on the first picture, but I cant read it. I don't think there should be a jumper there. What is the P/N on the IC? Check all the devices installed on the long heat sink.

[steves7839]

Re: samsung ln52a750r1fxza red light blinks

If the TV ever worked, a missing jumper is missing by design (i.e. an option) and should be left as is. With power disconnected, take Ohms readings between all voltage pins and ground. This should uncover the location causing the fuse to blow.

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

IC part is on the Hot side and number is 2A20112 the only thing i can think of is i shorted it when removing the big blob of solder from it that was shorting across three of it's pins, but it wasn't blowing the main fuse before . SIGH.....

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

this is the location on the IC where there was a big blob of solder i removed most of it and that's when the fuse started blowing, the two pins circled are still shorted together, I was given this set to repair two others in hopes of getting this one repaired to use for a while, it appears it has been worked on at least once and it pretty toasty, meaning that when i slightly move a component you can hear the solder cracking, maybe time for a fresh board???

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

thinking of removing ic and testing for fuse blowing? steve i removed the jumper i soldered in, i used the shop J picture as a reference thinking there was suppose to be a jumper there, as i said i have no idea who has been in here before, But i messed up somewhere when trying to reflow some joints, basic stuff, now i have the short, made a small problem worse. URG!!

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

thank you for all you help, I know when i am in over my head and now that i have a serious short i am near drowning, I'm opting for a replacement board, sucks, but thats how it goes, sometimes you win and sometimes you loose. thanks again to everybody.

[CapLeaker]

Re: samsung ln52a750r1fxza red light blinks

My guess is that you shot that PFC IC, maybe the gate drive circuit and some Mosfets. Pin 16 of that IC was VCC for the PFC IC. Pin 15 is the Master Mosfet drive terminal. So yep... shouldn't have soldered that bridge to those 2 pins.

[LITEZONER]

Re: samsung ln52a750r1fxza red light blinks

do you guys know if the power supply's are interchangeable on these is has the BN44-00201A I am looking at the BN44-00202A they look nearly the same? Thanks

[budm]

Re: samsung ln52a750r1fxza red light blinks

Shojimmy does not list any sub for the 201A.