No HV or VCC voltage after adding RTC module

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1 month 2 weeks ago #12479 by Sasam
I just started putting together my classic Rev 4 kit, purchased about a year ago. Constructed the low voltage circuit no problems.VIN input 9.38v, VCC at " Power, Front, RTC, and test point = 4.97v. so far so good.
Constructed HV circuit, tested, no buzzing or crackling, no smoking nothing is hot HV at test point 178.4v. // VCC 4.97 at test point. Yay all good so far.
Moving on to the RTC circuit and "Tick LED" (I'm using just a single LED for the tic) constructed the circuit, the RTC power light came on, but the "tick" LED did not. Turned power off to double check polarity all good. Powered back up still no tic. Powered down and tried the other LED still no tic, no buzzing or crackling or smoke, nothing getting hot.
Powered down to double check all my solder points all good.
Powered back up and the power led on the RTC is now not illuminated. The HV at the test point is 8.2v. // 8.6v at D1, // 8.2v at D2, // 8.4v at HV out on SV1, // 8.7v at middle leg of Q1, // 8.4v at positive terminal of C1.
VCC voltage remains 4.97 at SV1, and SV2. There is no voltage at the VCC test point or RTC SV4.
It was pretty exciting how well it was going. I have enough tubes to build four clocks so I really need some help to figure out where I went wrong. Should I just buy another kit or board and start over? Thanks for any advise.

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1 month 2 weeks ago #12480 by Ian
It doesn't sound like any known issue - one thing to be aware of, the HV turns off after 60 seconds from power on. If you need more time, briefly power off and on again.

Could that be the problem?

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1 month 2 weeks ago #12482 by Ty_Eeberfest
I find it very strange that VCC is present in some places and not in other places. The only way I can think of to explain it is a cut trace somewhere, though how that would happen during assembly is beyond me!

Can you post a good high resolution picture of the solder side of the board please?

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

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1 month 2 weeks ago #12488 by Sasam
Thank you Mr. Eeberfest for responding. I am really at a loss as to what has happened. All was good, then it wasn't??? If a trace got cut, how would I know as not to do it again? I am assuming, if that would be the case, I will need to purchase another PCB. Do you know If the same components from this Rev.4 work on the newer Rev.5 PCB. I saw where Ian has just the PCB and controller listed on Ebay?
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1 month 2 weeks ago #12489 by Ty_Eeberfest
Yes I find your problem to be a bit strange myself! I think the important clue is that you have VCC at some points and not at others. This needs to be investigated, and I'd appreciate it if you would do your meter tests (of VCC, don't worry about HV right now) one more time to confirm the findings.

Cut traces... are most commonly a defect when the boards are etched at the factory but that doesn't seem to be the case here. It is possible to cut or "lift" a trace by using too hot a soldering iron or by heating a pad for too long. Please examine the board closely (magnifier or binocular microscope) in the area of the RTC connection. In your picture I see some suspicious looking spots in that area but i can't tell exactly what I'm seeing.

Recommended soldering temperature is no greater than 400C / 750F. You should be using a fine tipped iron (not a "gun"!!!) and if it's not temperature controlled it should be 50 watts or less - 25 watts preferred.

Usually you can repair a cut/lifted trace by soldering on a "bodge wire" to complete the path of the cut trace. More about that, and about the subject of replacement boards, after we figure out what's actually wrong.

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

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1 month 2 weeks ago #12490 by Sasam
Okay, I have retested the VCC. SV1 and SV2 read 4.9v. The VCC test point and RTC SV4 remain at 0.00v.
My soldering iron is a 40w Weller and I am using a ST7 / 0.79 mm fine conical tip.
I use a desk mounted led lighted magnifier when soldering trying to be mindful of excessive heat. I used the same magnifier to look carefully at the area around the RTC and I'm not seeing anything that looks out of place. But keeping that in mind, I'm the one looking for help.

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