{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "5c1",
  "url": "https://circuitcodex.com/amps/5c1/",
  "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": "5c1",
    "name_style": "Wide-panel Champ-style",
    "family": "tweed",
    "era": {
      "start": 1953,
      "end": 1955
    },
    "wattage": 4,
    "tubes": [
      "6SJ7",
      "6V6GT",
      "5Y3GT"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "5Y3GT"
      },
      "bias": "cathode",
      "phase_inverter": "none",
      "tone_stack": "none"
    },
    "lineage": {
      "derived_from": [],
      "influenced": [
        "5e1"
      ]
    },
    "conventions": {
      "designators": "sequential"
    },
    "sources": [
      {
        "desc": "Fender 'Champ-Amp' Model 5C1 drawing (F-DH), schematic + layout sheets: every component value read directly from the published sheet — dual 75 kΩ input-jack resistors summed into a single 0.02 µF·600 V coupling cap; 6SJ7 grid-leak (contact) bias, no cathode resistor, 5 MΩ leak to ground; 2 MΩ screen dropper with a 0.05 µF·600 V bypass; 250 kΩ plate load; 0.02 µF·600 V interstage coupling into a 1 MΩ volume control; 6V6 grid off the pot wiper, cathode-biased on a shared 500 Ω/25 µF·25 V network. Power supply a two-resistor RC filter across three 8 µF·450 V cans, no choke: the reservoir feeds the 6V6 plate (via the OT primary) through a 500 Ω dropper, and a second 25 kΩ dropper off THAT node supplies a third rail shared by the 6V6 screen and the whole 6SJ7 plate/screen circuit — the screen is drawn off the far side of the 25 kΩ from its own plate, not off the plate's own node. The layout sheet's printed voltage chart (NOTICE: 'voltages read to ground with electronic volt meter, values shown +or-20%') gives +340 V at the reservoir, +320 V at the 500 Ω/25 kΩ junction that feeds the output transformer, +280 V at the shared 6V6-screen/6SJ7 node (lettered at the 6V6 screen), +300 V at the 6V6 plate pin, +16 V at the 6V6 cathode, and +130 V, +21 V and −0.5 V at the 6SJ7 plate, screen and grid. The drawing prints no transformer or output-transformer part numbers. Not reproduced here; archived at EL34World",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_champ_5c1_schem.pdf"
      },
      {
        "desc": "Wikipedia, Fender Champ — wide-panel 5C1 dating (1953-1955) and its place in the Champion-to-Champ transition",
        "url": "https://en.wikipedia.org/wiki/Fender_Champ"
      },
      {
        "desc": "Fender 'Champ-Amp Layout, Model 5C1' drawing (F-DH), page 2 of the same PDF — the source for the board-layout diagram's part order and point-to-point wiring. Redrawn from the published facts, never traced",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_champ_5c1_schem.pdf"
      }
    ],
    "verification": {
      "status": "verified",
      "date": "2026-08-08T00:00:00.000Z",
      "max_deviation_pct": 14.8
    },
    "added": "2026-08-08T00:00:00.000Z",
    "contributors": [
      "TheAnalogMaker"
    ]
  },
  "parts": {
    "notes": "Numbering follows the schematic. The AC-line section (power transformer, fuse, line cap) is drawn as annotation only and carries no designator. Values are from the published Champ 5C1 (F-DH) drawing.",
    "items": [
      {
        "ref": "R1",
        "part": "Carbon comp resistor",
        "value": "75 kΩ · ½ W",
        "role": "Input 1 series resistor, jack 1 tip → summing node ahead of C1"
      },
      {
        "ref": "R2",
        "part": "Carbon comp resistor",
        "value": "75 kΩ · ½ W",
        "role": "Input 2 series resistor, jack 2 tip → summing node ahead of C1"
      },
      {
        "ref": "R3",
        "part": "Carbon comp resistor",
        "value": "5 MΩ · ½ W",
        "role": "6SJ7 grid leak (contact bias — no cathode resistor)"
      },
      {
        "ref": "R4",
        "part": "Carbon comp resistor",
        "value": "2 MΩ · ½ W",
        "role": "6SJ7 screen dropper"
      },
      {
        "ref": "R5",
        "part": "Carbon comp resistor",
        "value": "250 kΩ · ½ W",
        "role": "6SJ7 plate load"
      },
      {
        "ref": "R6",
        "part": "Wirewound resistor",
        "value": "500 Ω · 2 W",
        "role": "6V6 cathode bias"
      },
      {
        "ref": "R7",
        "part": "Power resistor",
        "value": "500 Ω · 1 W",
        "role": "Rail dropper B+1→B+2"
      },
      {
        "ref": "R8",
        "part": "Power resistor",
        "value": "25 kΩ · 1 W",
        "role": "Rail dropper B+2→B+3"
      },
      {
        "ref": "VR1",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Volume"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 600 V",
        "role": "Input → 6SJ7 grid"
      },
      {
        "ref": "C2",
        "part": "Bypass capacitor",
        "value": "0.05 µF · 600 V",
        "role": "6SJ7 screen bypass"
      },
      {
        "ref": "C3",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 600 V",
        "role": "6SJ7 plate → volume pot"
      },
      {
        "ref": "C4",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "6V6 cathode bypass"
      },
      {
        "ref": "C5",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 450 V",
        "role": "Filter, B+1 (reservoir)"
      },
      {
        "ref": "C6",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 450 V",
        "role": "Filter, B+2"
      },
      {
        "ref": "C7",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 450 V",
        "role": "Filter, B+3"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "6SJ7",
        "role": "Single gain stage"
      },
      {
        "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": "T1",
        "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": "HT · 6.3 V · 5 V",
        "role": "HT secondary (voltage not marked; +340 V reservoir implies ≈345-0-345) + heater and rectifier windings"
      },
      {
        "ref": "—",
        "part": "Line capacitor",
        "value": "0.05 µF · 600 V",
        "role": "AC line to chassis, on the line side of the fuse"
      },
      {
        "ref": "—",
        "part": "Fuse",
        "value": "2 A",
        "role": "AC-line fuse"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Fender Champ 5C1 (F-DH) layout sheet, printed chart: +340 V at the rectifier, +320 V at the 500 Ω/25 kΩ junction, +280 V on the far side of the 25 kΩ (printed at the 6V6 screen, pin 4); 6V6 plate +300 V and cathode +16 V; 6SJ7 plate +130 V, screen +21 V and grid −0.5 V.",
    "nodes": {
      "BP2": {
        "chart": 320,
        "tol_pct": 20,
        "note": "the 500 Ω/25 kΩ junction, which feeds the output transformer's primary — a single 500 Ω dropper off the reservoir, no choke on this pre-5E1 circuit. The 6V6 plate pin itself prints +300 V, 20 V lower across the primary, whose resistance the model omits, so the plate simulates at this node's voltage"
      },
      "BP3": {
        "chart": 280,
        "tol_pct": 20,
        "note": "shared rail after the 25 kΩ dropper off BP2, printed at the 6V6 screen (pin 4) — feeds the 6V6 screen (drawn off the far side of the 25 kΩ from its own plate, not off BP2) and the whole 6SJ7 plate/screen circuit"
      },
      "P1": {
        "chart": 130,
        "tol_pct": 20,
        "note": "6SJ7 plate, printed pin value — gated like every other pin, and inside the chart's ±20 %. The stage around it is not reproduced: its grid and screen are reported rather than gated (see G1 and SG1), so this pass shows the plate voltage agrees, not that the 6SJ7's operating point does"
      },
      "SG1": {
        "chart": null,
        "note": "6SJ7 screen — the drawing prints +21 V here. Reported, not gated: the stage is grid-leak (contact) biased, the corpus's tube models carry no grid-current path, and so the deck holds the grid at 0 V (G1) and the tube's screen current does not follow the real stage's; the screen simulates well below the printed figure"
      },
      "G1": {
        "chart": null,
        "note": "6SJ7 grid — the drawing prints −0.5 V here, the contact bias the tube develops across its 5 MΩ leak. Reported, not gated: with no grid-current path in the corpus's tube models, nothing in this DC deck can pull the grid below 0 V"
      },
      "K2": {
        "chart": 16,
        "tol_pct": 20,
        "note": "6V6GT cathode, chart pin value (500 Ω, 25 µF bypass)"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BP2",
      "chart": 320,
      "sim": 324.383,
      "disputed": false,
      "dev_pct": 1.3696874999999942,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "the 500 Ω/25 kΩ junction, which feeds the output transformer's primary — a single 500 Ω dropper off the reservoir, no choke on this pre-5E1 circuit. The 6V6 plate pin itself prints +300 V, 20 V lower across the primary, whose resistance the model omits, so the plate simulates at this node's voltage",
      "dispute_note": ""
    },
    {
      "node": "BP3",
      "chart": 280,
      "sim": 249.775,
      "disputed": false,
      "dev_pct": 10.794642857142856,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "shared rail after the 25 kΩ dropper off BP2, printed at the 6V6 screen (pin 4) — feeds the 6V6 screen (drawn off the far side of the 25 kΩ from its own plate, not off BP2) and the whole 6SJ7 plate/screen circuit",
      "dispute_note": ""
    },
    {
      "node": "P1",
      "chart": 130,
      "sim": 149.277,
      "disputed": false,
      "dev_pct": 14.828461538461529,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "6SJ7 plate, printed pin value — gated like every other pin, and inside the chart's ±20 %. The stage around it is not reproduced: its grid and screen are reported rather than gated (see G1 and SG1), so this pass shows the plate voltage agrees, not that the 6SJ7's operating point does",
      "dispute_note": ""
    },
    {
      "node": "SG1",
      "chart": null,
      "sim": 12.062,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "6SJ7 screen — the drawing prints +21 V here. Reported, not gated: the stage is grid-leak (contact) biased, the corpus's tube models carry no grid-current path, and so the deck holds the grid at 0 V (G1) and the tube's screen current does not follow the real stage's; the screen simulates well below the printed figure",
      "dispute_note": ""
    },
    {
      "node": "G1",
      "chart": null,
      "sim": 0,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "6SJ7 grid — the drawing prints −0.5 V here, the contact bias the tube develops across its 5 MΩ leak. Reported, not gated: with no grid-current path in the corpus's tube models, nothing in this DC deck can pull the grid below 0 V",
      "dispute_note": ""
    },
    {
      "node": "K2",
      "chart": 16,
      "sim": 15.356,
      "disputed": false,
      "dev_pct": 4.025,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "6V6GT cathode, chart pin value (500 Ω, 25 µF bypass)",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Verified",
      "summary": "4 reference nodes are within tolerance. Maintainer verification is recorded for 2026-08-08; 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": "5c1-input-resistors-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "5c1"
      ],
      "title": "5C1 input resistors",
      "description": "The two 75 kΩ input resistors now sit in series between each jack and the first stage's coupling capacitor, as the factory drawing shows. Both drawings had placed them as shunts to ground with the jacks wired straight to the capacitor. No operating point changes.",
      "commit": "e51e2c44483d6aae5733bc827fc214ff2266da93",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/e51e2c44483d6aae5733bc827fc214ff2266da93"
    }
  ],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/5c1"
}