kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 10:19 am

eldenh wrote:... I mounted the board with the 4 screws that have metal pads assuming them to be important, but have omitted #s 4, 6, 7 expecting to have to remove the board to replace whatever had failed.

Trying to troubleshoot from your pencil sketches has been rather difficult because my eyes have trouble distinguishing the pencil lines from a grayish background. I choose to build a spreadsheet to help me find where I can try to probe with the board mounted. In doing so I found that Q219 is listed as "KN" and "G16". I can't make out the label in the underside photo, so don't know which is right.


That's excellent to recognize those screw pads; was there a good solid connection to the 12V negative, not just thru the little ground wire on pin 5 of CN201?

Good catch on the list i had it twice; on my board Q219 is "G16" N-fet IRL2502, and Q218 is "KN" P-fet 2SJ305.
kiev = kenny's innovative electric vehicle

eldenh
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 11:15 am

I read 1.0 ohm from pin 5 and the chassis.
2012 ES

kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 11:27 am

It has never been clear to me if you were testing in the car or on a work bench, so that is why i mentioned the need for a good ground for the board. The 4 screw pads are not connected to pin 5.

All the return current for charging the 12V aux has to return back to this board thru the housing. The Pin 5 wire is not the path we would want it to take, e.g charging at 60 Amps.

One is a signal ground, the other a power ground. Ultimately they are tied to the same reference level, but damage will occur if the power ground uses the signal ground as a return path.
kiev = kenny's innovative electric vehicle

eldenh
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Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 11:41 am

I've been using the chassis for LV ground when testing. I've been testing on the bench as I don't think I can make connection in the car and safely reach the dc-dc converter.
2012 ES

eldenh
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Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 2:57 pm

IC202 pin 13 switches from LO to HI when the 12v at the output wire is disconnected.

Why all the signal processing on that system?
2012 ES

eldenh
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Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 4:16 pm

I measured the voltage on all the pins of IC202: 1 is 0v, 2 is 0v, 3 is 15.5v, 4 is 4.66v, 5 is 0.17v, 6 is 2.27v, 7 is 0.15v, 8 is 1.63v, 9 is 0.10v, 10 is 3.26v, 11 is 0.08v, 12 is 0v, 13 is 0v, 14 is 0v. Pins 4/5 surprise me as the data sheet gives max differential voltage as 3.6v! R256 has 15.5v and 4.66v, R251 has 0.02 and 0.0v, R250 has 2.27 and 0.02v, R249 has 2.27 and 2.42v, and R248 has 4.66 and 2.42v.
2012 ES

kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 4:28 pm

That was a good test. You can measure the response at the collector of Q223 and what pin 12 of IC207 (both on the bottom layer) are seeing from the top, there is a tiny trace coming out from under the CN201 connector on the side opposite of the CN201 label, this trace terminates into a little double via with the tiny holes. This point is the line shown on the schematic on Q223. That pin should change state depending upon presence or absence of the Output 12V battery connection.

The logic would be that the PWM would not start unless there is a 12V on the output side, so when Output 12V is present then the double via should read Hi, when no 12V it will go Lo.

Just saw you measurements on IC202, it is a quad comparator but i don't have but the -A,-B or -D of the quad traced yet, only the -C circuit. But all the output readings are consistent with the input voltages.
Last edited by kiev on Mon Nov 09, 2020 7:31 am, edited 3 times in total.
kiev = kenny's innovative electric vehicle

coulomb
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 4:49 pm

[ Edit: The below is all wrong. I was confusing IC201 and IC202. Sigh. Sorry for the confusion. ]

eldenh wrote:I measured the voltage on all the pins of IC202: 1 is 0v, 2 is 0v...

0 V on pin 2 is bad; according to Kenny's traced schematic, it should be +5 V. Perhaps it connects to Vref, pin 16? You didn't give a voltage for pins 15 (Vcc) or 16 (Vref). I assume that Vcc must be 15.5 V or slightly above, for pin 3 to have 15.5 V.

Pins 4 and 5 are the oscillator. The oscillator could be stopped due to pin 8 (soft start) being low, though above 0.2 V it should be soft starting. It's not clear to me whether you need to keep pulsing pin 8 low to get more than one pulse from the output; I suspect that you do. In normal operation, pin 8 should be above 5.0 V.

Actually, if the block diagram is accurate, the oscillator should keep going, and other parts of the circuit should keep the output low despite the oscillator running. So it may be that there is a problem with the oscillator parts. There are probably only 2-3 parts connected to pins 4 and 5.
Last edited by coulomb on Thu Nov 05, 2020 9:29 pm, edited 1 time in total.

eldenh
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Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 5:23 pm

When I witnessed the changes at IC202 pin 13, I monitored the gate of Q203 and saw no changes from a logic HI.
2012 ES

eldenh
Posts: 65
Joined: Sat Oct 03, 2015 7:18 pm
Location: Port Angeles, WA

Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 5:28 pm

Mike, I think you are confused about IC202. It is a 14 pin quad comparator device with V+ on pin 3 and V- on pin 12. It is located near the double large capacitors by the output fuse.
2012 ES

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