JVC 56P575 no power

[pac.attack76]

Ok, guys, looking at the board where the words "live" and "isolated" read upright, the pins are like this:

. .
. . . With the cap out to the left. Now, going from left to right, left to right, i got: -.033, -14.06, -.003, -1.26, .000

Not sure if i did this right. Red on right side of cap since the other side has a plus mark. Set to VDC.

[pac.attack76]

Did i do this right. If not, i can hit it again.

[rca2000]

You did it BACKWARDS. Put the black probe lea don the hot ground. Use ther red or positive one---for all of the other readings.

BUT...i did NOT see any 171 volts on ANY pins of that chip. Are you SURE_-you got all of the pins? 2 of them are scattered from the otherrs--remember. if you did NOT...then check those 2 large resistoirs beside of that chip...and see if they are OPEN. They likely read LESS than one ohm. If OPEN--that ahip IS shorted.

[pac.attack76]

Originally Posted by rca2000

You did it BACKWARDS. Put the black probe lea don the hot ground. Use ther red or positive one---for all of the other readings.

BUT...i did NOT see any 171 volts on ANY pins of that chip. Are you SURE_-you got all of the pins? 2 of them are scattered from the otherrs--remember. if you did NOT...then check those 2 large resistoirs beside of that chip...and see if they are OPEN. They likely read LESS than one ohm. If OPEN--that ahip IS shorted.

Ok, i figured as much. I'll hit it again tonight or no later than tomorrow. I'll need to get this part, whatever it ends up being, ordered so i can get it in soon.

[pac.attack76]

Yeah, i missed two pins. Layout is actually:

. . .
. . .
.

Now from left to right with black on cap neg. i get:
169.8, 13.73, .017,
.000, 1.309, .004,
.000
Note these are taken with board out of set but still plugged to ac.

[rca2000]

At this point...I would re-check ALL diodes and any transistors near that IC..on th HOT side of it (within that white drawn area surrounding HALF of the transformer and optocoupler.) be SURE to check any diodes and make sure none are shorted.


If you do NOT find anthing...that i would order than IC and the optocoupler--as a "just in case". Your voltages indicate the IC is NOT shorted and is getting full voltage from the big cap and it ALSO looks to be geting its "start voltage" too. I would gues it is just bad.

[pac.attack76]

I have a guy in the area that looked at the board the other day and he thinks the optocoupler is bad. Probably $1 or $2. Hes wondering what the readings should be if it were good. Getting voltages on the large cap and STK.