coulomb
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Thu Nov 05, 2020 9:25 pm

eldenh wrote:Mike, I think you are confused about IC202.

D'Oh! I was confusing IC201 and IC202. Sigh.

kiev
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IC207 details

Thu Nov 05, 2020 10:53 pm

Here are the last two AND gates [from the IC202-A -B comparators] that affect the signal to the IC206 OR gate pin 12. These could be stopping the PWM if the OR gate is Hi.

So that one OR gate on pin 12 is a combination of 3 conditions: the temperature sensor, the 12V on output, and the level of the TP201 secondary supply voltage nominally "15V".
Image
Last edited by kiev on Mon Nov 09, 2020 7:41 am, edited 4 times in total.
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kiev
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Re: IC207 details

Fri Nov 06, 2020 12:30 am

i don't know how you knew to check the voltages of IC202, but that was a stroke of genius and it seems to be a direct hit on what is causing your problem.

There are 4 comparators that set a threshold voltage on the + pin and compare it to a signal on the - pin. Two of these use the TP201 voltage (shown as 15V but it can vary depending upon the HV Input and the operation of IC101 as it is the low-side secondary of TR105) as the input signal, the other two use the 12V Output voltage as the signal.

The 5V supply is used to set the threshold and for the pullup on the open collector output. A positive feedback resistor is added to create hysteresis filtering to prevent ringing or oscillation in the output signal when passing thru the threshold level.

In your measurements of IC202 all of the + pin input voltages are nearly zero, meaning that either the 15V TP201 and 12V Output voltages are too high (exceeding the threshold level), or that the 5V supply is not reaching that area of the board and creating the threshold voltage of the resistor divider networks, or that the chip is just bad.

The 5V voltage divider networks for the Threshold (Non-inverting inputs pins 5 and 7) seem like the 5V is missing. The 5V is available to measure on the top layer as double vias with the larger diameter holes, one is near C236 on the end of IC202, the other between IC205 and the edge of the board near R245. The 15V double via is close to the second 5V also.

One counterpoint to my bad chip theory is that you measured a response when disconnecting the 12V from the Output, so at least that seems to indicate correct operation of the comparator on those pins. But there still could be a defective 5V.
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eldenh
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Fri Nov 06, 2020 9:23 am

Thanks for the research and explanations. I found only 0.28v at both of those vias. But I've now created a larger problem. My probing created an arc around Q110 and blew R129 off the board and I believe Q110 has failed and some of the copper is melted. I can't read any value for the loose resistor either visually or with my vom. R128 is only partially readable and I am having trouble getting a measurement.
2012 ES

kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Fri Nov 06, 2020 10:34 am

Oh no, can you explain where and how you were probing when this occurred? Q110 is in the HV section and i don't understand how that would be affected by probing in the LV section?

R128 has a value of 100Ω and is a "0603" smd size.

R129 has a value of 1.5Ω and is a "1206" smd size.
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eldenh
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Fri Nov 06, 2020 10:57 am

I was checking around to verify that my batteries were supplying enough voltage to have a working board. When I tested Vsub I read 0 and probed the terminals of Q110 to see why. I'd forgotten that I should be checking with my other probe on the HV neutral. :oops:
2012 ES

kiev
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IC202 Comparator

Fri Nov 06, 2020 11:55 pm

i didn't like how the drawing was folded around on the IC202-C Comparator section and it was incomplete;
[edit] added additional findings
traced out the -D Comparator path;
found a linkage to CN201 pin 6 to the control function and the Common Vias on the transistors.
Image
Last edited by kiev on Mon Nov 09, 2020 7:44 am, edited 6 times in total.
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eldenh
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Sat Nov 07, 2020 11:17 am

I find it difficult to read the resistor values in the drawings, so I want to ask for an explanation of the functional properties of the comparator and signal processing of their outputs. It looks like A & B sections determine that a 5v power ail is between certain limits and there is feedback around the comparators to provide different levels to switch back. Sections C & D function similarly for the 12v output line with Q223-225 being used to verify the presence of 15v and 5v power. Does this upper limit serve to switch off IC201 when the output line reaches it's intended max voltage {14.4v}? I had assumed that that limit was controlled by voltage feedback to IC201.

Where is the 5v that sections A & B are monitoring derived?
2012 ES

kiev
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Sat Nov 07, 2020 12:09 pm

The 5V is made on the bottom layer, IC209, from the "15V" of the secondary seen at TP201 with respect to chassis ground.

Are the resistor values blurry or too small or what is the problem? The schematics are image files that you can right click and save to your device, then use an image viewer and zoom in if necessary.

i will repost the last schematic with notes about the switching threshold voltage levels.

The set point reference is developed from the 5V and the feedback resistor from the output to the + terminal causes a hysteresis action to filter out oscillation as the signal passes thru the set point on the way up and back down. When the signal matches or exceeds the V Threshold(Hi) it switches output to the Hi state; Then when the signal is headed back lower than the low Threshold, the output switches to the Lo state.

ref from application notes
Image

For the -C and -D comparators, the "Signal" is level of the Output 12V to decide something; the -A and -B are looking at the TP201 "15V" supply as the "Signal" to decide when to do something. There will be a certain time delay as the secondary voltage is coming up; the comparator outputs can be used to regulate or turn something on or off based upon the voltage level of the "15V". i don't know what all that is yet, there is still a lot of stuff to sort thru in that LV section.

The -C leg is what was traced earlier in crude form to determine that it was one of the causes for the PWM to start or not by commanding pin 8 of IC201. Both Pins 8 or 9 of IC201 can be used turn off or restart the PWM switching.
Last edited by kiev on Sat Nov 07, 2020 12:41 pm, edited 2 times in total.
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eldenh
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Re: Gen1 DCDC Converter Troubleshooting and Repair

Sat Nov 07, 2020 12:36 pm

Thanks for the advice. When I opened the image in a new tab the values and labels are much more readable.
2012 ES

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