I am attempting to test a samsung power supply board to verify the pfc ic is working. I am powering up the board with my isolation transformer. The board turns on fine but when I attempt to connect the ground for the scope probe, it trips out the isolator. I was taught not to 'float my scope' so I am wondering if I should test without connecting the ground lead or would that be asking for trouble? Not sure how else to test, I don't have a portable scope. I could plug direct to mains power but that would bypass the safety factor.
-
-
All you need is your DMM and set it to VDC. Plug the PSU in and it should turn on (depends on what Samsung PSU it is). Check the voltage on your main filter cap. Should be something like 380VDC if the PFC is working. That is all there is to it. No oscilloscope needed.
Do NOT test the primary with an oscilloscope without the isolation transformer. That will blow up your PSU and your oscilloscope.Last edited by CapLeaker; 07-13-2025, 03:01 PM. -
Thanks - wish it was that simple. These boards are know to fail due to a disc capacitor cracking, leading the failure of at least one power mosfet which in turn, can cause a failure of the pfc ic. Replacing the shorted mosfet and 4 disc caps, resulted in a nice little mosfet explosion. The next step is to verify that the pfc ic is or is not damaged - that is what I am attempting to do.Comment
-
Vizio e601i-A3 - Has Sound and Display, But No Backlight - Bad Power Supply Board or Bad LED Bulbs ?I was given this TV from my great uncle. He said it just wouldn't turn on one day out of nowhere, replaced the TV, and gave it to me to possibly fix and use for myself.
Upon bringing it home and plugging it up, it showed a standby light.
I powered it on and without a flashlight, the display showed the "V" but the lighting is very dim, but visible.
The screen seems to blackout and stay black, but with a flashlight I can see the display.
With my Playstation 4 connected via HDMI, and running a game I can hear sound.
Assuming... -
Hi, this is my personal laptop, which the original board (lets call it Board A) blew up PU8700 (TPS51486), making a hole on the board, i had left the laptop at my desk one day with the battery fully charged and didn't touch it for a week, but when i tried to turn it on it didn't
Thought the battery was dead, so i plugged in the charger then tried to power on, the power LED blinked once, charged LED still orange, unplugged the charger, plugged in again and I noticed the "magic smoke" smell, so i unplugged the charger, removed the back cover and saw the blown IC (the "magic... -
I picked up this TV from Facebook Marketplace, original owner described it as "screen went black after a pop" and I hoped to see an obvious fuse or cap to replace. Doesn't seem to be the case, but my experience and electrical knowledge are kind of limited for this.
The power board (BN44-00445A, see attached) turns on and Vs and Va seem to momentarily have power, then they steadily drain to zero over a minute or two as if they're only getting power from capacitors. I've been measuring Vs and Va from the test pads, with and without the other boards connected to the power board... -
I hope this is the right forum to post in despite not technically being a repair, but still a question of swapping boards.
I thought I'd explore the possibility to upgrade an existing working Samsung ue55nu7096u with the logic board (and power board if needed) of a newer model (ue55ru7105k) of the same size and appearance (and resolution). The reason being I'd like the extra inputs of that board including component in, an extra HDMI port and bluetooth. Its panel is broken so I have no use for the board otherwise.
The models launched in 2018 and 2019 respectively.... -
Samsung LN46C630K1F – Intermittent Backlight, BN44-00341B Power Board
Summary for TL-DR readers:
• Backlight is intermittent, may come on with TV boot or not. No flickering, never fails during TV on.
• Have obtained Samsung schematic & service documents - Can upload if helpful.
• Have read ALL applicable threads
• C1818 and CP820 replaced as low hanging fruit
• CN802 data taken for normal and failed BL operation. SUMMARY: Pin 2 - 5vDet = 3.52 @normal, 0.0 @BL fail. Pin 6 - EPWM = 1.631 @normal, 1.058 @BL fail.
• VCC pin (18) of PFC...
Comment