Another Dead Samsung HPT4254X

[Ltank]

Hi Guys. I had one of these sets last month that I gave up on. So now I got another set in. I checked the serial # and it is a different set. This set was dead. There not any shorts to the YSus or XSus boards
The manual on page 29 shows steps;
SMPS CN801
Pin 3 : STB 5V (good 5.11vdc)
No----Replace the SMPS (I tried a new spare with same results)
Pin 2 PS-ON : Check to see if it is 0V----Yes Replace Main Board
(FlowChart Misprint Schemtic and board has it as Oin #1) 3.88vdc measured with chasis gnd reference
According to the manual the P.S_On is from the Conrtol board not the main board. The P.S. BN44-00161A CN801 and CN807 both have a PS_On command that are jumpers between te two on the PS itself.
So with or without loads, the new BN44-00161A does not turn on. Put another Control. I put in a new Power Supply and aControl Board from a supplier. Still does not turn on
Is the PS_On a actve Low or High? Normally 3.8 vdc is enough. have seen
Samsung sets turn on with lows and others high, The manual does not specify

[kenny1070]

Re: Another Dead Samsung HPT4254X

There appears to be a lot of misprints in the sch.
(CN101 is listed on the Main - when it's actually on the Side A/V)

I would start with verifying the 5 volt return from the Main board - it should be at Pin 2 on CN1101 ( or TP104 on the Main board itself).
From there you can confirm its location back to the PSU/SMPS by simply ohming out the harness and verifying its pin location on CN801.
(This will also show if there are any voltage drops across the tabs)

Don't worry about CN807 (at least not yet) as it is a secondary output supply and doesn't affect powering up the psu.

I really can't help much more than that, without knowing the output voltages of the psu/smps.

Please post some pics. and pin voltages (standby & pwr/on).