{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "5f1",
  "url": "https://circuitcodex.com/amps/5f1/",
  "attribution": "The Analog Maker / Circuit Codex",
  "license": "https://creativecommons.org/licenses/by-sa/4.0/",
  "revision": "ebddc3fd2cf887dca010bbe60487d7391ea6c052",
  "scope": "DC and drawing checks have separate coverage. See included check results and the circuit page; not a dimensioned build template or a physical-build certification.",
  "metadata": {
    "id": "5f1",
    "name_style": "Tweed Champ-style",
    "family": "tweed",
    "era": {
      "start": 1958,
      "end": 1964
    },
    "wattage": 5,
    "tubes": [
      "12AX7",
      "6V6GT",
      "5Y3GT"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "5Y3GT"
      },
      "bias": "cathode",
      "phase_inverter": "none",
      "tone_stack": "none"
    },
    "lineage": {
      "derived_from": [
        "5e1"
      ],
      "influenced": [
        "aa764"
      ]
    },
    "conventions": {
      "designators": "sequential"
    },
    "sources": [
      {
        "desc": "Rob Robinette, 'How Amps Work' (5F1-based walkthrough) — component roles, PT 325-0-325, B+ node structure (its 16uF caps / dual-10k droppers figures were corrected by the drawing read-off: 16/8/8uF, 10k+22k)",
        "url": "https://robrobinette.com/How_Amps_Work.htm"
      },
      {
        "desc": "ampbooks.com classic-circuit analysis (5E1 revision) — cross-reference for stage values and 6V6 cathode operating point",
        "url": "https://www.ampbooks.com/mobile/classic-circuits/fender-champ-5e1/"
      },
      {
        "desc": "Fender 5F1 published voltage chart — all node/pin values read directly from the published drawing (2026-07-18); no factory drawing reproduced here. Scans are indexed in the EL34World archive",
        "url": "https://el34world.com/charts/TubeAmpSchematics.htm"
      },
      {
        "desc": "Fender 'Champ-Amp' 5F1 layout drawing (K-EE), page 2 — the source for the order the board-layout drawing on this page places parts on the eyelet board. Redrawn from the published facts, never traced",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_champ_5f1_schem.pdf"
      }
    ],
    "verification": {
      "status": "verified",
      "date": "2026-07-18T00:00:00.000Z",
      "max_deviation_pct": 14.9
    },
    "contributors": [
      "TheAnalogMaker"
    ]
  },
  "parts": {
    "notes": "Numbering follows the schematic; gaps (R12, C2, C4) are intentional. Power transformer and chassis hardware are listed at the end without designators.",
    "items": [
      {
        "ref": "R1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Input leak, jack 1's tip to ground (the V1A grid returns through R3)"
      },
      {
        "ref": "R2",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Input 2 grid stopper"
      },
      {
        "ref": "R3",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Input 1 grid stopper"
      },
      {
        "ref": "R4",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V1A cathode bias"
      },
      {
        "ref": "R5",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1A plate load"
      },
      {
        "ref": "R6",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V1B cathode bias"
      },
      {
        "ref": "R7",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1B plate load"
      },
      {
        "ref": "R8",
        "part": "Wirewound resistor",
        "value": "470 Ω · 5 W",
        "role": "6V6 cathode bias"
      },
      {
        "ref": "R9",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "6V6 grid leak"
      },
      {
        "ref": "R10",
        "part": "Power resistor",
        "value": "10 kΩ · 2 W",
        "role": "Rail dropper B+1→B+2"
      },
      {
        "ref": "R11",
        "part": "Power resistor",
        "value": "22 kΩ · 2 W",
        "role": "Rail dropper B+2→B+3"
      },
      {
        "ref": "R13",
        "part": "Carbon comp resistor",
        "value": "22 kΩ · ½ W",
        "role": "Negative feedback, speaker→V1B cathode"
      },
      {
        "ref": "VR1",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Volume"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 600 V",
        "role": "V1A → volume"
      },
      {
        "ref": "C3",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 600 V",
        "role": "V1B → 6V6 grid"
      },
      {
        "ref": "C5",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Filter, B+1"
      },
      {
        "ref": "C6",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "6V6 cathode bypass"
      },
      {
        "ref": "C7",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 450 V",
        "role": "Filter, B+2"
      },
      {
        "ref": "C8",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 450 V",
        "role": "Filter, B+3"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Both gain stages (V1A/V1B)"
      },
      {
        "ref": "V2",
        "part": "Power tube",
        "value": "6V6GT",
        "role": "Single-ended output"
      },
      {
        "ref": "V3",
        "part": "Rectifier tube",
        "value": "5Y3GT",
        "role": "Full-wave rectifier (V3A/V3B)"
      },
      {
        "ref": "T2",
        "part": "Output transformer",
        "value": "≈5 kΩ : 8 Ω",
        "role": "Single-ended output (impedance not marked on the drawing; typical SE 6V6 load)"
      },
      {
        "ref": "—",
        "part": "Power transformer",
        "value": "325-0-325 V · 6.3 V · 5 V",
        "role": "HT + heaters + rectifier filament"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Published Fender 5F1 chart (drawing read-off by GM, 2026-07-18); pin-6/pin-3 values applied to both 12AX7 sections (symmetric stages)",
    "nodes": {
      "BP2": {
        "chart": 295,
        "tol_pct": 5,
        "note": "6V6 screen node, after the 10 kΩ dropper (R10)"
      },
      "BP3": {
        "chart": 250,
        "tol_pct": 5,
        "note": "preamp node, after the 22 kΩ dropper (R11)"
      },
      "P1A": {
        "chart": 150,
        "tol_pct": 20,
        "note": "12AX7 plate, chart pin value"
      },
      "P1B": {
        "chart": 150,
        "tol_pct": 20,
        "note": "12AX7 plate, chart pin value"
      },
      "K1A": {
        "chart": 1.5,
        "tol_pct": 20,
        "note": "12AX7 cathode, chart pin value"
      },
      "K1B": {
        "chart": 1.5,
        "tol_pct": 20,
        "note": "12AX7 cathode (NFB 22k parallels at DC)"
      },
      "K2": {
        "chart": 18,
        "tol_pct": 20,
        "note": "6V6GT cathode, chart pin 8"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BP2",
      "chart": 295,
      "sim": 291.53,
      "disputed": false,
      "dev_pct": 1.1762711864406872,
      "tol_pct": 5,
      "gated": true,
      "within": true,
      "note": "6V6 screen node, after the 10 kΩ dropper (R10)",
      "dispute_note": ""
    },
    {
      "node": "BP3",
      "chart": 250,
      "sim": 252.117,
      "disputed": false,
      "dev_pct": 0.8467999999999962,
      "tol_pct": 5,
      "gated": true,
      "within": true,
      "note": "preamp node, after the 22 kΩ dropper (R11)",
      "dispute_note": ""
    },
    {
      "node": "P1A",
      "chart": 150,
      "sim": 163.857,
      "disputed": false,
      "dev_pct": 9.238,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AX7 plate, chart pin value",
      "dispute_note": ""
    },
    {
      "node": "P1B",
      "chart": 150,
      "sim": 161.23,
      "disputed": false,
      "dev_pct": 7.486666666666659,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AX7 plate, chart pin value",
      "dispute_note": ""
    },
    {
      "node": "K1A",
      "chart": 1.5,
      "sim": 1.324,
      "disputed": false,
      "dev_pct": 11.733333333333329,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AX7 cathode, chart pin value",
      "dispute_note": ""
    },
    {
      "node": "K1B",
      "chart": 1.5,
      "sim": 1.276,
      "disputed": false,
      "dev_pct": 14.933333333333332,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AX7 cathode (NFB 22k parallels at DC)",
      "dispute_note": ""
    },
    {
      "node": "K2",
      "chart": 18,
      "sim": 18.028,
      "disputed": false,
      "dev_pct": 0.15555555555554829,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "6V6GT cathode, chart pin 8",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Verified",
      "summary": "7 reference nodes are within tolerance. Maintainer verification is recorded for 2026-07-18; changes since then are awaiting maintainer re-review.",
      "details": [
        "The circuit's facts (netlist, reference voltages, parts list, both drawings' connections, capacitor polarity marks and heater declarations) have changed since the maintainer's review, or no review fingerprint is on record yet. The badge stands on its date until the maintainer re-reviews.",
        "This compares simulated DC conditions with the cited reference. It does not test sound, physical construction or every part of the circuit."
      ],
      "tone": "checked"
    },
    {
      "id": "schematic",
      "title": "Schematic against DC model",
      "status": "Checked",
      "summary": "Connectivity of modelled components is checked on every change.",
      "details": [
        "Parts outside the DC model need separate checks and source review."
      ],
      "tone": "checked"
    },
    {
      "id": "board",
      "title": "Board against DC model",
      "status": "Checked",
      "summary": "Connectivity of modelled components is checked on every change.",
      "details": [
        "This does not establish heater wiring or physical spacing."
      ],
      "tone": "checked"
    },
    {
      "id": "drawings",
      "title": "Schematic against board",
      "status": "No open findings",
      "summary": "No disagreement is listed in the published comparison.",
      "details": [
        "A finding identifies a difference or a coverage gap. The factory source must decide which drawing, if either, needs correction.",
        "0 sheet-only parts are explicitly excluded. Heaters and the pilot lamp are checked separately."
      ],
      "tone": "checked"
    },
    {
      "id": "heaters",
      "title": "Heater and filament wiring",
      "status": "Checked",
      "summary": "The declared heater circuits cover the drawing and pass their separate wiring check.",
      "details": [],
      "tone": "checked"
    },
    {
      "id": "polarity",
      "title": "Capacitor polarity",
      "status": "Checked",
      "summary": "4 capacitor markings agree with the model's voltage ordering.",
      "details": [
        "This check uses DC voltage ordering; source review establishes markings the model cannot decide."
      ],
      "tone": "checked"
    }
  ],
  "corrections": [
    {
      "id": "5f1-second-input-resistor-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "5f1"
      ],
      "title": "5F1 second input resistor",
      "description": "Each input jack now has its own 68 kΩ resistor into the first stage, as the factory drawing shows. The parts list, schematic and board had carried one shared resistor. No operating point changes.",
      "commit": "a6a37d7977c62a032dcac75ff3630263f3f12ca6",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/a6a37d7977c62a032dcac75ff3630263f3f12ca6"
    }
  ],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/5f1"
}