troubleshooting DAC 19M008 power supply

[budm]

Re: troubleshooting DAC 19M008 power supply

But for the fuse for the 5V which is used by the Main board to blow open, the main board must be drawing too much current from the power supply board.

[budm]

Re: troubleshooting DAC 19M008 power supply

You may have active short, see page 59, you will see that the V5A feeds two regulator U4, U6. Check the resistance of the output pins (2, 4) and ground and see what you have, the short can also be in the T-CON board which is fed by 3.3v vreg U6. You may also want to disconnect the ribbon cables to the LCD panel and see if the 5v will be OK, I hope you have more than 1 fuse, you can use 0.47 Ohm 1/4w in place of the fuse for testing.

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

on both U4 and U6, both the leftmost (#2 ?) of the 3 pins are short to ground (using the heads of the mounting screws), could both regulators have gone bad?

[jetadm123]

Re: troubleshooting DAC 19M008 power supply

You may be measuring the ground pin of the regulator against ground, which will show a short. Suggest to download the datasheet for the regulator and compare the pin you're measuring against the datasheet.

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

You may be measuring the ground pin of the regulator against ground, which will show a short. Suggest to download the datasheet for the regulator and compare the pin you're measuring against the datasheet.

found a datasheet for the AMC1117 regulator, the pin I was measuring was pin 1 which is ground, pin 2 and 4 are output and neither regulator is short at these pins

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

I'm going to order some more fuses, this time I'm going to power up the power supply board all by itself, to see if it pops the fuse.

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

Just replaced the F102 fuse, with power supply board not connected to the main board I get 5v at the 5v pin on the main board connector, so it seems to be the main board that's blowing the fuse.

Are there any other parts on the main board that can be tested with power off?

[selldoor]

Re: troubleshooting DAC 19M008 power supply

Just replaced the F102 fuse, with power supply board not connected to the main board I get 5v at the 5v pin on the main board connector, so it seems to be the main board that's blowing the fuse.

Are there any other parts on the main board that can be tested with power off?

Diodes

[budm]

Re: troubleshooting DAC 19M008 power supply

You may have active short, see page 59, you will see that the V5A feeds two regulator U4, U6. Check the resistance of the output pins (2, 4) and ground and see what you have, the short can also be in the T-CON board which is fed by 3.3v vreg U6. You may also want to disconnect the ribbon cables to the LCD panel and see if the 5v will be OK, I hope you have more than 1 fuse, you can use 0.47 Ohm 1/4w in place of the fuse for testing.

Did you disconnect the cable as I suggested?

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

Did you disconnect the cable as I suggested?

Just powered it up with the two LCD panel cables disconnected, was unable to disconnect cable from speaker/button board. Fuse popped again. Do I have a bad main board?

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

Is there a trick to removing the speaker/button-board ribbon cable from the main board. The two LCD panel cables were easy enough, but can't see how to disconnect other cable.

[Mark369]

Re: troubleshooting DAC 19M008 power supply

just pull out no trick

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

Got it. I was looking for some kind of release like the other two connectors. Guess I'll get another main board since it looks like there isn't much serviceable on this board and the regulators aren't shorting. Found one on Ebay for $10.

[mikeh1]

Re: troubleshooting DAC 19M008 power supply

Just got around to ordering the main board. I will post the results once I get it installed. Keeping my fingers crossed!

[mikeh1]

FIXED!! troubleshooting DAC 19M008 power supply

FIXED!! Thanks to Sabre504 and budm for all your help AND patience! Hopefully I'll get another 7 years out of this monitor.