zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Mon Aug 03, 2020 10:51 am

So first of all, thank you for your patience and the great support you are giving me! That helps me a lot.

I have two multimeters here and they both measure a frequency of around 130 Hz between Pin 6 and 7 of TR301. But this reading is not stable at all and they both show 0V. I think the MOSFET might not be chopping, but I can not confirm this without a proper scope which I dont have at the moment.

I checked every part I could reach and measure in circuit on the bottom with the power turned off. Is there any way, I can check IC317?

kiev
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Mon Aug 03, 2020 11:14 am

i have to run right now, but i think this is it:

NCP4641 is a CMOS 150 mA linear voltage regulator with high input voltage and ultra−low supply current.
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zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Mon Aug 03, 2020 1:59 pm

The IC317 does only get 0.6 V as input voltage. This results in a 0 V output. I do not think that IC317 has shorted out, but I can easally desolder it to try, if you think that happened. I also noticed that after I connect my supply, the voltage is around 1V and then slowly decreases to 0.6 V

kiev
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Mon Aug 03, 2020 4:36 pm

That is not likely the problem-- it is not getting any voltage thru the transformer and your test just verified it from another direction. you could test it on the board with a current limited power supply, just put 6 volts on the input and should see 5 on the output, but

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. There may be discussion of this on page 9. If i get time i will try to trace it out and draw it up better than the hand sketch, but i have some medical appts tomorrow and will be off line most of the day.
kiev = kenny's innovative electric vehicle

kiev
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Tue Aug 04, 2020 4:22 am

There is also an optocoupler pc 314 on the bottom side that sends the signal from ic318 over to the gate driver ic702, but the waffle plate probably covers it from probing. Several small resistors on top side near corner of transformer are the voltage divider for ic318.
kiev = kenny's innovative electric vehicle

zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Tue Aug 04, 2020 4:24 pm

Today I bought myself a scope and I can conform that the MOSFET is not chopping at all. Everything around IC318 looks fine to me and all components on the bottom side are covered by the plate. Even if I could reach them for probing I would not be able to replace them. So I think I have to desolder the plate.

Should I buy a desoldering station with an integrated vacuum pump for this job or how would you desolder it?

kiev
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Tue Aug 04, 2020 5:31 pm

That's what i used. Some of the junctions have wide copper traces and a big thermal mass, and i damaged a few by pulling and forcing them out while there was still too much solder down in the hole.

i would have done better to add some flux to those pins, then a hot iron and try to draw the solder up toward the top with wick or wire if necessary and make sure the holes were clean. Add solder to a joint to increase the thermal mass and capillary action sometimes works.

or use a hot iron and wooden chop stick to repeatedly heat-and-pry, heat the pins and pry up the board from underneath to walk the board up the pins and use wick to clean up the holes once its off the plate and on the bench.
kiev = kenny's innovative electric vehicle

zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Wed Aug 05, 2020 1:24 pm

Thank you so much for your time and effort! I just ordered a desoldering station which will be delivered in three weeks. (I ordered a JBC one and JBC stuff takes forever to ship to me) As soon as I get it I will be posting my progress here.

I will in addition to your suggestions add leaded solder in order to decrease the melting temperature and preheat the PCB to 80°C
i would have done better to add some flux to those pins, then a hot iron and try to draw the solder up toward the top with wick or wire if necessary and make sure the holes were clean. Add solder to a joint to increase the thermal mass and capillary action sometimes works.

kiev
Posts: 1227
Joined: Sun May 03, 2015 7:15 am
Location: The Heart o' Dixie
Contact: Website

Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Thu Aug 06, 2020 1:47 pm

Might as well try to order some new parts while you wait, the ic318 and ic702, maybe even the FET, TR310, unless you are sure it is good. But why not fresh it all up while you are in there, you don't want to have to go back in there again.
kiev = kenny's innovative electric vehicle

zetafunction
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Re: Troubleshooting and repair for On-board Charger (OBC), DC-DC Converter

Tue Aug 25, 2020 12:27 pm

After waiting several weeks for my desoldering iron I finally got rid of the waffle plate. All components around IC702 measure out fine to me and assuming IC702 is a TI OPA2369 I can measure 2.4V between V+ and V-. How could I check, if this IC is working or would you recommend looking at something else instead?

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