Hey guys
I'm kind of at my wits end with this repair. I'm wondering if anyone could maybe offer some advice.
Subject: DARFON 4H.V1561.091 4-channel backlight inverter
Symptoms:
Instant shutdown with any tube connected to CH4 (barely noticeable blink)
With no tube on CH4 runs all other channels for 2 seconds then shuts down
Does the same with known-good tubes.
Known-good inverter does not shut down with the tubes that go with this board.
Fuse is intact.
Transformer primary and secondary resistances
4: S:1067 P:0.7
3: S:1067 P:0.68
2: S:1077 P:0.7
1: S:1067 P:0.7
Swapped the CH4 transformer for one of the others anyway, same result.
Gate-Source-Drain resistances on the driver FETs are consistent between channels.
The two lytics on the board are Rubycon but I measured them anyway. They're fine for both ESR and capacity.
All resistors on the board measure within tolerance.
Just to make sure it's not the power supply I hooked wires up to it and powered it up from a battery. Same results.
It seems that CH4 alone is used for something by the controller because it's the only one connected through at D12. Moving that diode down that row also moves the instant-shutdown fault to other channels. Removing the diode makes all channels work for 2 seconds.
The controller is an LX6512.
Any ideas?
Thanks
I'm kind of at my wits end with this repair. I'm wondering if anyone could maybe offer some advice.
Subject: DARFON 4H.V1561.091 4-channel backlight inverter
Symptoms:
Instant shutdown with any tube connected to CH4 (barely noticeable blink)
With no tube on CH4 runs all other channels for 2 seconds then shuts down
Does the same with known-good tubes.
Known-good inverter does not shut down with the tubes that go with this board.
Fuse is intact.
Transformer primary and secondary resistances
4: S:1067 P:0.7
3: S:1067 P:0.68
2: S:1077 P:0.7
1: S:1067 P:0.7
Swapped the CH4 transformer for one of the others anyway, same result.
Gate-Source-Drain resistances on the driver FETs are consistent between channels.
The two lytics on the board are Rubycon but I measured them anyway. They're fine for both ESR and capacity.
All resistors on the board measure within tolerance.
Just to make sure it's not the power supply I hooked wires up to it and powered it up from a battery. Same results.
It seems that CH4 alone is used for something by the controller because it's the only one connected through at D12. Moving that diode down that row also moves the instant-shutdown fault to other channels. Removing the diode makes all channels work for 2 seconds.
The controller is an LX6512.
Any ideas?
Thanks
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