DSE GE6987 LCD TV main board (303C3393073) - DDR SDRAM voltage
This board is almost identical to the Haier 55E3500, and in both controllers, DDR SDRAM is integrated.
When connected to a power supply and LCD controller tester, a brief "Loading" message appeared before the picture snowed out, but it did start up OK under unknown circumstances.
An analysis of the circuit revealed that the DDR 1.8V regulator was set for 1.5V (270R between regulator Adjust-Output and 56R between regulator Adjust-GND; 120R between Adjust-GND sets output voltage to 1.8V); even though the Haier circuit uses the MSD3393 (ATSC) as its controller, the GE6987 uses the MSD6306 (DVB) with the same pinout.
Searching for sets which used the MSD6306 (and a block diagram of this IC) revealed that some use a 1.5V DDR voltage while others used 1.8V; the absolute maximum voltage for DDR3 (1.5V +/- 0.075V) SDRAM is 1.975V, so changing the voltage of the DDR regulator to 1.8V with a 240R resistor added between Adjust-Output (even though there was a minor risk of catastrophic failure) resulted in consistent startup of this board without excessive current draw.
When connected to a power supply and LCD controller tester, a brief "Loading" message appeared before the picture snowed out, but it did start up OK under unknown circumstances.
An analysis of the circuit revealed that the DDR 1.8V regulator was set for 1.5V (270R between regulator Adjust-Output and 56R between regulator Adjust-GND; 120R between Adjust-GND sets output voltage to 1.8V); even though the Haier circuit uses the MSD3393 (ATSC) as its controller, the GE6987 uses the MSD6306 (DVB) with the same pinout.
Searching for sets which used the MSD6306 (and a block diagram of this IC) revealed that some use a 1.5V DDR voltage while others used 1.8V; the absolute maximum voltage for DDR3 (1.5V +/- 0.075V) SDRAM is 1.975V, so changing the voltage of the DDR regulator to 1.8V with a 240R resistor added between Adjust-Output (even though there was a minor risk of catastrophic failure) resulted in consistent startup of this board without excessive current draw.
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