Fixing a DAC-19M005 Power Supply - check my DX:
Here is my proposed fix of the DAC-19M005 power supply found on a number of 19" LCDs, mine is an ACER1916 WA . The unit had no power, no lights, and no sound. On dis-assembly I found only one bad cap, 161V on the main filter capacitor, and no blown fuses. Following are my diagnoses, testing, and proposed parts list.
1. I replaced all 7 caps with matching Panasonic FM series, although several had very low ESR. These OEM's were Capxons KF series made in before mid-2007.
2. On boot the same symtoms continued. I then tested the DC output voltages and found 0.0 instead of 5V, and less than 1V instead of the 13.8V expected. Checking the bridge rectifier (DB100) with the power off I got about 20 ohms on 5 leg pairs but pair 2-3 (the A/C's) was 0.0 ohms. So this component is bad.
3. Next I checked the pair of Mosfets Q205 and Q206 and pulled the one which seem to be shorted, and on retesting found the fet had about 25 ohms with the gate charged, but would not discharge to the touch. Since one failed and the other is the same make and age, I will replace both of these units.
4. Since I couldn't get any voltage readings out of the Shottky diodes D102 and D103 which should be the 5V and 13.8 volts spec, I pulled one and tested it on the bench this way....black on cathode, red on anode looks open, reverse read 25 ohms....looks then to be good, but not sure about this VOM test and the one still on the board, so will order one of these just in case.
5. I found an SMD fuse on the back of the board, F200, which had not blown, F103 fuse was still good too at zero ohms, and I finally also checked the transistor Q102 with 20 and 50 ohms so figure it is OK too.
Here is the parts I want to now replace with new ones I'll be ordering from Digikey :
DB100 is marked D2SB 60A which is a 600V 2A Bridge Rectifier ; will order Digikey no. KBP206GDI-ND
Q205+ Q206 marked 40T03GP which traced to form TO-220 N channel 30V 40A Mosfet; order two 497-3187-5-ND
D102 or D103 marked SBT 150 10 is Schottky diode size 10 100V 15A ; order one 869-1025-ND
F200 SMD fuse in case I blow the repair testing, .125"x.035"with a 5(?) on it; order 1206SFF500F/32CT-ND
Please critique my diagnoses, testing, and of course the parts to be ordered for accuracy...and A Big Thank You !
1. I replaced all 7 caps with matching Panasonic FM series, although several had very low ESR. These OEM's were Capxons KF series made in before mid-2007.
2. On boot the same symtoms continued. I then tested the DC output voltages and found 0.0 instead of 5V, and less than 1V instead of the 13.8V expected. Checking the bridge rectifier (DB100) with the power off I got about 20 ohms on 5 leg pairs but pair 2-3 (the A/C's) was 0.0 ohms. So this component is bad.
3. Next I checked the pair of Mosfets Q205 and Q206 and pulled the one which seem to be shorted, and on retesting found the fet had about 25 ohms with the gate charged, but would not discharge to the touch. Since one failed and the other is the same make and age, I will replace both of these units.
4. Since I couldn't get any voltage readings out of the Shottky diodes D102 and D103 which should be the 5V and 13.8 volts spec, I pulled one and tested it on the bench this way....black on cathode, red on anode looks open, reverse read 25 ohms....looks then to be good, but not sure about this VOM test and the one still on the board, so will order one of these just in case.
5. I found an SMD fuse on the back of the board, F200, which had not blown, F103 fuse was still good too at zero ohms, and I finally also checked the transistor Q102 with 20 and 50 ohms so figure it is OK too.
Here is the parts I want to now replace with new ones I'll be ordering from Digikey :
DB100 is marked D2SB 60A which is a 600V 2A Bridge Rectifier ; will order Digikey no. KBP206GDI-ND
Q205+ Q206 marked 40T03GP which traced to form TO-220 N channel 30V 40A Mosfet; order two 497-3187-5-ND
D102 or D103 marked SBT 150 10 is Schottky diode size 10 100V 15A ; order one 869-1025-ND
F200 SMD fuse in case I blow the repair testing, .125"x.035"with a 5(?) on it; order 1206SFF500F/32CT-ND
Please critique my diagnoses, testing, and of course the parts to be ordered for accuracy...and A Big Thank You !
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