Dell P2421DC power board 715GA678-P02-001-0H1S - dead after component replacement

Hello,
I am repairing a Dell P2421DC monitor power board, part number 715GA678-P02-001-0H1S.
Original fault:

Q901 (IPA70R600P7SXKSA1) was shorted drain-to-source
RSF100JB-73-0R56 (0.56 Ω sense resistor) had visible coating damage
R929 (10 kΩ 0805) had visible burn damage and measured open circuit

Components replaced:

Q901 — replaced with new IPA70R600P7SXKSA1
RSF100JB-73-0R56 — replaced with new
R929 — replaced with new 10 kΩ 0805

Current symptoms:

Bulk capacitors charge normally after power on (confirmed)
No switching occurs
Board completely dead — no output voltages
Dim bulb tester shows nothing — no current draw
PS_ON pin grounded to GND — no change
All fuses good: F9901, F901, F902
BD9901 bridge rectifier tests good
TH9902 thermistor tests good
All startup resistors R802-R805 test good

Suspected faulty component:
U801 (OZ582TSGN) — PFC/PWM controller

Questions:
Is U801 likely damaged in this failure scenario?
Is there any way to confirm U801 failure without live voltage measurements?
Is there a known replacement or equivalent for OZ582TSGN?
Are there any other components commonly damaged in this failure mode that we may have missed?
Does anyone know where I can purchase a replacement board 715GA678-P02-001-0H1S? I have been searching for weeks without success. Any leads on suppliers, eBay sellers, or other sources would be greatly appreciated.

Thank you in advance for any help!


AI: Can you provide any live voltage readings around U801, especially VCC/startup voltage, GATE/DRV, CS, and the HV startup path, with mains applied?
Not live voltage, but verified:
R802 = 10 kΩ
R803 = 300 kΩ
R804 = 10 kΩ
R805 = 300 kΩ
AI: Do you have clear photos (top and bottom) of the area around Q901/U801, and have you checked nearby gate/snubber/drive parts (gate resistor, diode, optocoupler, clamp/snubber components) for secondary damage?

lisman007 wrote:

Q901 - replaced with new IPA70R600P7SXKSA1

From which IC is this transistor controlled, probably it is also defective.
Because the one you specified U801 is probably the driver from the backlight.
You can buy the whole monitor used for the price of the power supply module.
Dell P2421 24" possibly has the same power supply board.
https://amso.pl/product-pol-294329-Monitor-De...hFJSvB_LHuOOMbntd9P3LmH7xNVhN6n4aAttqEALw_wcB

OZ582SGN 16pin light driver
pin.1 power supply / pin.13 ground
pin.10,11,15,16 output to LED lines

no datasheet and application u. work


As "gone" field to replace:
- drive system plus
- all the small parts connected to the field unit (in the gate, drain and source)
* so that there are no surprises later on

Which IC is the driver for the field effect?
LD75922

Thank you for your response.

I have identified U901 - it is a SOT-23-6 package with marking code "Ttb" (second line: XB1 B8). It is located directly between Q901 (IPA70R600P7S) and U801 (OZ582TSGN), which matches the gate driver position you described.

I cannot find LD75922 anywhere (Mouser, Digi-Key, eBay). I found ZXGD3003E6QTA (by Diodes Inc.), which is a SOT-23-6 single MOSFET gate driver - is this a suitable replacement for U901?

Also, OZ582TSGN (U801) is not available from any Western distributor. If U901 replacement does not fix the board, where do you recommend sourcing OZ582TSGN?

Current status:
- All fuses good
- Q901 replaced (new IPA70R600P7S)
- R929 and sense resistor replaced
- Bulk capacitors charge normally
- No switching, board completely dead

It is to be 7592, PFC controller datasheet attached.

Look 715GA052 PSU Link
- also 715GA052 PSU




p.s
LD7591GS replaced by L6562D

Thank you very much!!!
U901 is SOT-23-6 package. L6562D is SOIC-8 — is there a SOT-23-6 compatible substitute, or do I need the exact LD7592S?

Ttb- Sot23-6 LD5537B1GL

https://www.lazada.co.id/products/ic-pwm-ld55...tb-sot23-6-tb-ib1-ib3-ic-pwm-i8622182552.html

See, check , if you can replace LD5537= PF6003A= PF6005A
https://www.elektroda.pl/rtvforum/topic3754707.html