I’m also trying to use the APPLE backlight Inverter Bd instead of the CHINA Backlight Inverter bd to solve the BRIGHTNESS issue. Still working on it!
On PWM signal, I just used 3v DCin (I ordered a PWM generator to supply 13kHz, 3V, but not received yet. Not sure why I am only getting 12.51 Vout when using the APPLE backlight inverter bd. I suspect either EN or PWM is why I am only getting on 12.51 Vout CN2.1
BE CAREFUL - DANGER HIGH VOLTAGE.
Here’s the Voltage measurements I took.
iMac with Apple Inverter, no PSU and no LogicBoard
INVERTER VOLTAGES
- Vout 12.51V (CN2.1)
- Vin 12.58v (CN1.2)
- ENA 3.22v (CN1.1)
- PWM 3.02v (CN1.3)
CA-255 China Inverter board
iMac with China inverter, no PSU and no LogicBoard
INVERTER VOLTAGES
- Vout 32.5v (CN4.1)
- Vout 87.6v (CN4.1) with LCD disconnected
- Vin 11.93v (CN1.1)
- ENA 4.64v (CN1.3)
- PWM 0v (CN1.4)
iMac with Apple inverter, PSU and LogicBoard (normal 2011 iMac EMC2429)
INVERTER VOLTAGES
- Vout 36.5v (CN2.1)
- Vin 11.8v (CN1.2)
- ENA 3.22v (CN1.1)
- PWM 3.08v (CN1.3)
I am using Yeeco USB Power Supply for the 3v PWM and 3.25v ENA
https://www.amazon.com/dp/B07VDRM4PG?psc...
I am using 12V/10A adapter for the Vin 12V to the Inverter board
OK, I tried to use three 12V adapters as follows.
- 12V/10A adapter into Apple backlight inverter board
- 12V/5A adapter into HDMI driver board
- 12V/5A adapter into CIG. lighter to USB that power two Yeeco USB Step Down Power Supplies and one Yeeco is set to 3.3V to supply the EN signal, the other Yeeco is set to 3.3V to supply the XY-KPWM signal generator for the 13kHz 3.3V signal for PWM
So the Apple backlight inverter board has the 12Vin , 3.3V on EN, 3.3V/13kHz on PWM
GND for the 12Vin is connector to the 12V adapter , GND for PWM / EN is wire from screw hole on backlight to signal generator and Yeeco.
I plugged in 12V adapter for Apple backlight first, then 12V adapter for HDMI driver next, then 12V adapter for USB step down last and the LCD screen comes on for about a second with the image, but then goes to BLACK.
Not sure what to do next?
ok,
I swapped the inverter board between working 2011 iMac machine and the iMac “Monitor”
the 2011 iMac machine still works great, LCD lights up and works.
the iMac “Monitor” has the same condition, where the LCD lights up with correct image for only 1-2 seconds , then goes black.
so LCD is good, Inverter bd is good
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