Sanyo DP42740 no power

[triplefour]

Re: Sanyo DP42740 no power

wow that IS a great picture. i will have to learn to use them as a resource since my camera is not that great

[budm]

Re: Sanyo DP42740 no power

OK I took a quick look at the bottom side of the board, I see why you are not getting the voltage at those two main filter caps, those two black relays have to be turned on (PS_ON) by the main board board.

[triplefour]

Re: Sanyo DP42740 no power

i cant measure ce203 without flipping the board over. but is it safe to run the board like that? and do all the other connectors have to be plugged in or can i just plug in the main power? do i need to have at least one screw into the chassis to have it grounded?

[budm]

Re: Sanyo DP42740 no power

You can run the board by itself without having any other board connected to it since we are trying to find out if the STBY power supply is working or not first. Just put the board on card board. Just be real careful sine you are working in the primary side of the circuit.

[triplefour]

Re: Sanyo DP42740 no power

ok i did that and i see 150v across ce203

[budm]

Re: Sanyo DP42740 no power

OK, that is good, next I need to trace out the connections in the stby power supply section.

[triplefour]

Re: Sanyo DP42740 no power

i still dont know how u do that just from pictures of the board... i can barely tell whats going where! is there an easy way to think about it?

[budm]

Re: Sanyo DP42740 no power

"i still dont know how u do that just from pictures of the board." That is why good clear pictures are important.

[budm]

Re: Sanyo DP42740 no power

OK, board not plugged into the out, check the resistance between test point 1 and 2.
Check the Diode in red. Get the P/N of that SMPS IC.
Apply the power and then check the DC voltage right at the two legs of the startup cap that I circle.

[triplefour]

Re: Sanyo DP42740 no power

resistance between 1 and 2 is 0.5ohms
when i put my meter in diode mode, i get 620 when i have the black probe on the side with the line, and 1 with the probes reversed.
when in resistance mode i get 35kohms with black on line and 55kohms with probes reversed.
the numbers on the IC are
TB5AH
6754MR

the DC voltage across the legs on cap rj15 is fluctuating ...as low as 6v and as high as 20v

thank you!

[budm]

Re: Sanyo DP42740 no power

"the DC voltage across the legs on cap rj15 is fluctuating ...as low as 6v and as high as 20v"
OK, it is trying to run but it is stuck in the loop. So it can be that startup cap is bad, or shorted circuit in the secondary side, so check those two diodes to see if they are OK. If they are not shorted, then try replacing that cap.

[triplefour]

Re: Sanyo DP42740 no power

rectifier 1 seems to be shorted because i get 0.6ohms resistance either way i put the probes.
rectifier 2 gets 170 ohms resistance one way and infinite the other way, so im assuming thats fine?

how do i know if i can reliably test a diode in circuit or not? i remember on a previous post i had to take a diode out of circuit to test it...?

[triplefour]

Re: Sanyo DP42740 no power

on rectifier1 it says
LT1106
B3100

[budm]

Re: Sanyo DP42740 no power

Take it out and retest just to be sure it is the diode. Getting close!

[triplefour]

Re: Sanyo DP42740 no power

that must not be what it says because the datasheet i find for that is nothing like a rectifier diode...

[budm]

Re: Sanyo DP42740 no power

See post 34, I just updated it.

[budm]

Re: Sanyo DP42740 no power

OK, I am going to bed, a little tire from looking at the pictures.
Try again tomorrow, night.

[triplefour]

Re: Sanyo DP42740 no power

ugh...my soldering iron sucks, and i suck at using it. i think i may have lifted the trace on this one. how does one go about fixing that?

[triplefour]

Re: Sanyo DP42740 no power

the rectifier IS definitely shorted. continuity both ways when out of circuit.

[martino]

Re: Sanyo DP42740 no power

ugh...my soldering iron sucks, and i suck at using it. i think i may have lifted the trace on this one. how does one go about fixing that?

Scratch the green of the copper to the right of the injury and solder component a bit under an angle,not too bad of an injury there..
Keep tip of solder iron clean,and add a bit of your own solder to the solder on the board when you try to lift a component,often it melts a lot better then.