Troubleshooting and repair for On-board Charger (OBC)

[kiev]

No that is not a TI chip it is JRC, i posted on the previous page that ic702 is a gate driver chip,
viewtopic.php?p=41344#p41352

i have a datasheet listed as NJM2369_E, which i could send you if you can't find it.

On which pins did you measure that 2.4 voltage? i assume you are powering the top board with the 12V power supply as before?

[zetafunction]

Oh, thank you very much!

I can measure nothing between OUT and GND and I do not even see anything with my oscilloscope there. FB is switching and between IN and GND I can measure no voltage.

[kiev]

i don't see the timebase or ch1 volts/div, but i'm guessing that it's 5V/div and it's hitting about 16V peak. And that is the FB signal, which is coming from the voltage reference ic318 and the resistor network on the other side of the board.



i'll study on that datasheet, but it seems that the ic702 is not working.

check optocoupler pc314, but if it is not working then no FB would get back to the ic702 from the ic318.

How about all the little passives, resistors and capacitors around ic702, pc314, and ic318?

[zetafunction]

It is 1.2V/Div, so it is really low. I will now check pc314.

[zetafunction]

I just checked the diode in PC314 and it reads fine. Should I desolder it to really test the component? All passives measure out fine in circuit and do not seem to be damaged even under a microscope.

[kiev]

This is the first time to ever have a failure like this, so it's a learning experience. i did a quick trace of this area some time ago but never drew up a schematic, but now i wish i had.

It's not clear if the FB signal on the scope was transferred from the VR chip ic318 on top thru the optocoupler [toshiba TLP127] then to the Gate driver chip ic702.
It appears to be a 50Hz signal, so i suspect it is picking up some stray electric field.

But if it is real, then the opto is probably okay, and you measured the photodiode as okay, which is what gets triggered by the VR output pulled up by the 16V on C845 and the little resistor network on pin 4 of ic318.

Can you take a reading on pin 4 of ic318, gnd is pin 5. Also what is the input voltage on pin 3?

[zetafunction]

I just realised that my oscilloscope probe was damaged and the measurements were wrong, since there was no GND connected. Sorry for that.

The FB line of IC702 is not switching and steady at 2.4V.

IC318 outputs nothing between REF (Pin 4) and ANODE (Pin 5)

[kiev]

Was there any voltage on the input, pin 3?

i found my original notes on tracing all this and will try to post a photo of them in case it might help, although it is not pretty.

[zetafunction]

I was just about to measure Pin 1 so I plugged in my power supply when I noticed that something has to be wrong. The supply displayed a too high power consumption at 2.747 W. I first thought, my wireing is wrong or I somewhere do have a short. I double checked everything and then I realised a current draw of 229mA, very similar to skykloggers original measurements.

After some measurements, TR310 is chopping again, and IC317 is producing a 5V rail! For the scope measurements in the post before I soldered small wires to the resistor of IC318 and I also measured the pins of IC702 the same way. I think there was a broken soldering joint which I accidentally fixed! I just took off all components regarding IC702/IC318 and resoldered them with good quality solder. The board seems to be fixed to me now.

Before I solder the waffle plate back on, should I take any pictures or measurements off the board for further reference?

[kiev]

that's great news. Would you be able to measure the voltage on the electrolytic caps, C845, C841 and C369?

And if not too much trouble the input and output of the VR, IC318?

If you were to guess or try to narrow it down to which resistors may have had the poor solder joint--the little one between pin 4 and 5 of IC318? the little one by C844 near IC702? Did you happen to get a picture of the area around IC702 after you pulled the waffle plate?

here are some notes from previous posts, not sure if they would have helped find this issue or not, but will repeat them for future troubleshooting:

There is a 330 Ohm resistor from pin 4 of ic702 to the gate of TR301. It has test point solder blobs on each end that you might be able to reach. Maybe it is open circuit?

and

IC702 (on bottom side) provides the gate drive for the FET, so it is likely not doing it's job. And IC318 (on upper side) provides the feedback signal to ic702, so it will be one or the other of those two chips, or some little passive component in those circuits, resistor, cap, diode, etc.

or bad solder joint of a passive.