No HV or VCC voltage after adding RTC module

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6 months 2 weeks ago #12491 by Ty_Eeberfest
Okay it sounds like you are using the right soldering equipment and techniques.

I've marked some of the spots that seem suspicious on the picture below. The picture isn't clear enough for me to tell if I'm marking fried spots or just flux residue,

Check that R11 is soldered well. VCC passes through from the component side to the solder side on one end of R11. Yeah it's supposed to be a plated through hole but don't count on it. If the resistor's lead is solder well then it doesn't rely on the plating alone.

I advise visually following the VCC trace on the solder side. From the point of view of the picture it starts at the bottom of R11 and heads off to the right. That trace is feeding all the things you say have no VCC and none of the things you say have good VCC. So it, and R11 solder, are the main suspects.


Look into it later when the dust is clearing off the crater.
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6 months 2 weeks ago #12492 by Sasam
I have attached 2 more really tight photos of the areas you circled (man it really looks bad that close up).
I can see a little puckering in those areas. Is that what we are looking for and shouldn't be there?
You mentioned to check R11, now that's interesting? The PCB has a spot for "R11" but no where in the instructions I downloaded does it mention or call for anything going in that spot, so it is empty.
There is however a 3k resistor in "R8".
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6 months 2 weeks ago #12493 by Ty_Eeberfest
According to the schematic in the construction manual there's a 10K resistor that goes in the R11 spot. Not sure about where in the text it tells you to install it. It should not be necessary to have R11 in place for VCC to get distributed completely (plated thru hole) but I think you should go ahead and install it anyway, just in case the hole didn't get plated or something.

But before putting in R11, take your ohm meter and read from the "bottom" (from picture's point of view) to the VCC pin of SV1 and then to the VCC pin of SV4. Let me know what you read. My guess is that you'll have good continuity from R11 to SV1 and NO continuity to SV4. We'll see.

I still can't tell what I'm seeing in the pictures - flux residue or damage. It would be helpful if you would thoroughly clean the board with flux remover and a toothbrush (or isopropyl alcohol if you don't have real flux remover) and then take some close-ups with really good light.

Also I still want you to carefully inspect the trace that goes from the bottom of R11 off to the right (picture POV again).


Look into it later when the dust is clearing off the crater.
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6 months 2 weeks ago #12494 by Sasam
Okay, cleaned the board (that makes a difference).
I have continuity from R11 to VCC SV1 as shown by the green line on the photo.
There is also continuity from R11 to the 5th pin on IC2 as shown by the green line on the photo. I see nothing amiss with the trace from R11 to pin 5 on IC2.
There is no continuity from R11 to VCC on SV4 as you suspected.
Added two more tight photos I hope are beneficial.
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6 months 2 weeks ago #12495 by Sasam
After installing the 10K resister in R11 I now get 1.47v at the VCC test point and at the SV4 VCC.

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6 months 2 weeks ago #12496 by Ty_Eeberfest
Looks much better cleaned. Most of the suspicious looking spots disappeared.

Enough of R11, I think we can rule out that trace. I have another test and inspection for you. First check continuity from SV2 VCC to SV4 VCC. I think you will have no continuity but let's be sure.

If you have no continuity, then, using the picture below, inspect the highlighted trace. Note that it is on the component side of the board this time. Also note that it hits a number of places: C7, IC2 Pin 7, SV7 Pin 2. So you could narrow down what part of the trace to inspect by checking continuity from SV2 VCC to each of those points - see where you lose it.

I hope this gets some results because I'm almost out of ideas!!


Look into it later when the dust is clearing off the crater.
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