# Debug an Imported Altium Board From the First-Spin Symptom Give Flux the first-spin symptom on an imported Altium board. See it diagnose a regulator divider, fix the resistor, and update the BOM. Written by [Ryan Fitzgerald](https://flux.seobdtools.com/ryanf) Published Nov 2026 - 3 min read ![Debug an Imported Altium Board From the First-Spin Symptom](https://flux.seobdtools.com/p/assets/blogs/first-spin-debug-imported-altium-board/main.webp) Flux can diagnose a first-spin fault from the symptom on an imported Altium design, correct the circuit, and make the BOM match. On a LimeSDR-USB 1v4 test import, it traced a nominal 3.3 V rail reading about 6 V to a feedback resistor and corrected the divider to predict 3.31 V. ## Import the design. Give Flux the symptom. We used the public LimeSDR-USB 1v4 Altium project: a 12-layer SDR board with 858 parts. Before import, we deliberately changed one regulator feedback resistor, R180, from 10 kΩ to 20 kΩ. **This fault was planted for the test. It was not a fault in the shipped LimeSDR design.** After import, we gave Flux the bring-up symptom without identifying the component or the cause. Use a prompt like this: > With a current-limited 12 V supply, the nominal 3.3 V regulator output measures about 6.0 V with the downstream load disconnected. Diagnose the cause from this design, check the vendor datasheet, and fix it. Explain the predicted voltage before and after the change. Verify the changed component and connectivity. The symptom describes the test scenario. Flux had to find the relevant regulator and its feedback network in the imported design. 1. **Diagnose.** Flux identified IC27, an ADP2386 regulator, and traced its feedback divider through R180 and R184. It obtained and read the ADP2386 datasheet, then calculated the output from the saved resistor values. 2. **Fix the value.** The 20 kΩ top resistor predicted 6.03 V. Flux changed R180 to 10 kΩ, which predicted 3.31 V with the existing 2.21 kΩ bottom resistor. 3. **Make the BOM match.** The first change saved the correct resistance, but the imported part name still said 20 kΩ. We sent one short follow-up to correct the purchasing identity. ![Flux identifies a feedback divider that predicts 6.03 V and changes the top resistor to 10 kΩ for 3.315 V](https://flux.seobdtools.com/p/assets/blogs/first-spin-debug-imported-altium-board/diagnosis.webp) Flux connected the reported rail voltage to the divider values in the imported design. The follow-up was direct: > The BOM still says 20k. Please fix it so the build is right. Flux replaced the incorrectly named instance with the 10 kΩ part and verified the saved BOM. The sequence was **diagnose, fix the value, then make the BOM match**. It took the symptom prompt and one follow-up. ## Why one resistor explains the voltage The [ADP2386 datasheet](https://www.analog.com/media/en/technical-documentation/data-sheets/adp2386.pdf), Rev. C, page 15, gives the output-voltage equation and the recommended divider values. The regulator holds its feedback input at a nominal 0.6 V: `VOUT = 0.6 × (1 + RTOP / RBOTTOM)` - **Before:** `0.6 × (1 + 20 / 2.21) = 6.03 V`. - **After:** `0.6 × (1 + 10 / 2.21) = 3.31 V`. Table 6 specifies 10 kΩ and 2.21 kΩ for a 3.3 V output. Flux used that datasheet evidence to explain both the symptom and the correction, rather than selecting a resistor from the rail name alone. ![Flux schematic of the IC27 3.3 V buck regulator: L1 to VCC3P3, output capacitors C385 and C386, and the feedback divider R180 10 kΩ over R184 2.21 kΩ to the FB pin](https://flux.seobdtools.com/p/assets/blogs/first-spin-debug-imported-altium-board/regulator-schematic-v5.webp) R180 is now 10 kΩ. R184 remains 2.21 kΩ. The feedback connections are unchanged. ## Check the saved circuit and the BOM A corrected value and a purchasing record must agree. We checked both after the follow-up: - **Resistance:** R180 is saved as 10,000 Ω, ±1%. - **BOM:** the line names a 10 kΩ 0402 resistor, Yageo `RC0402FR-0710KL`. - **Connectivity:** R180 still connects VCC3P3 to the IC27 feedback net. The feedback net still connects IC27:FB, R180, and R184; R184 still connects to ground. ![Flux BOM line for R180 with a 10k part name, quantity one, 0.01 megaohm value, and RC0402FR-0710KL manufacturer part number](https://flux.seobdtools.com/p/assets/blogs/first-spin-debug-imported-altium-board/bom.webp) The corrected BOM line identifies the same 10 kΩ value as the schematic. ## Start with the evidence you have Bring the original design and the symptom into the same project. State the supply conditions, measured voltage, and load state. Ask Flux to explain the cause, make the targeted change, and verify the saved value, purchasing identity, and connections. For a circuit-response question, see [SPICE simulation on imported Altium and Cadence boards](https://flux.seobdtools.com/p/blog/spice-simulation-imported-altium-cadence-boards). That workflow starts with an existing circuit and produces DC, frequency-response, and transient results. Source design: [LimeSDR-USB by MyriadRF](https://github.com/myriadrf/LimeSDR-USB), licensed under CC BY 3.0. The test modification was the R180 value change described above. [Start Free Trial](https://flux.seobdtools.com/signup) ## About the author [Ryan Fitzgerald](https://flux.seobdtools.com/ryanf) Electronics Engineer at Flux Ryan is an electronics and electrical systems engineer with a focus on bridging the gap between deep learning intelligent algorithms and innovative hardware design. Find him on Flux [@ryanf](https://flux.seobdtools.com/ryanf) Let’s start building Build your big idea together with Flux. All you need to do is describe what you want to make, or what problem you want to solve. Flux will work with you to make it a reality. ![Close-up photo of a PCB made with Flux, with an ESP32 module, buttons, and a microSD slot.](https://flux.seobdtools.com/p/assets/blogs/miscellaneous/sidebar-cta-pcb.webp) [Try it Free](https://flux.seobdtools.com/signup) ## Related Content [ ![Teal technical illustration of two circuit boards in open enclosures, with an exponential step-response curve and a low-pass response diagram](https://flux.seobdtools.com/p/assets/blogs/spice-simulation-imported-altium-cadence-boards/main.webp) ### Run SPICE on Your Imported Altium and Cadence Boards 4 Min Read](https://flux.seobdtools.com/p/blog/spice-simulation-imported-altium-cadence-boards)[ ![a space-themed background with stars and a floating astronaut helmet to the left. 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