Projects/NexusNX3702Repair

[edit] Nexus NX-3702 Television Repair Notes

TV set is made by Nexus. It's a 32" LCD TV.

Is it the power supply board? (CE4-2, 37HA47)
Power is dropping on all pins except the 3.3v standby
- Tying PON to 3.3V triggers power supply board to come up
- Removed line to CPU board and jumpered set to come on
  - All voltages seemed steady after this
  - CPU board was dropping the (now disconnected) PON pin trying to trigger reset

Is it the back light inverter board? (Model V183-XXXA, CPT 370WA03 Rev01)
Tested all of the transformers using info found online
- None are shorted.
- None seem open.
Can't tell so far if the backlight board talks to CPU board thru PSU
- If it does, is it telling CPU board to reboot?
Discovered that letting BL_ON pin going to inverter board float triggers it to come on. Also tried tying to 5vdc
- Backlight board has been ruled out, it came on and ran fine

Is it the CPU board? (Part number 37HA32)
- CPU board has a RS232 port wired to connector on side (see below)
CPU board is telling the PSU to power cycle
Capacitors look fine?
The issue is the CPU board is rebooting in a loop

Is it the LCD panel? (Chunghwa CLAA370WA03 )
- Disconnected (carefully) the HVD + Power cable
- CPU board still resets

RS232 data port on side of set via 1/8" phono jack
- Pinout is as follows
  - Tip = Serial pin 2 on terminal
  - Ring = Serial pin 3 on terminal
  - Sleeve = Ground on terminal

Terminal should be 115200/8/n/1

Upon doing this, the following line shows up and repeats as set reboots:

SupraHD1.7- ***}}Zoran ThreadX OS Abstraction Layer v1.1

CPU board seems to be the culprit. It reboots over and over

Could see static from TV for a split second upon TV rebooting once backlight was forced on.

TV is rebooting, perhaps when the OSD data is supposed to come up?

Culprit is probably the CPU board.