{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "5f4",
  "url": "https://circuitcodex.com/amps/5f4/",
  "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": "5f4",
    "name_style": "Tweed Super-style",
    "family": "tweed",
    "era": {
      "start": 1957,
      "end": 1960
    },
    "wattage": 26,
    "tubes": [
      "12AY7",
      "12AX7",
      "12AX7",
      "6L6G",
      "6L6G",
      "5U4G"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "5U4G"
      },
      "bias": "fixed",
      "phase_inverter": "cathodyne",
      "tone_stack": "cathode-follower-tb"
    },
    "lineage": {
      "derived_from": [
        "5e4a"
      ],
      "influenced": []
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "Fender 'Super-Amp' Model 5F4 drawing (C-EG): every component value AND the printed voltage chart read directly from the published schematic (2026-07-18; tone network and phase inverter re-read at lug level 2026-08-03) — 12AY7 two-channel front end (68k stoppers, 1M leaks, shared 820Ω/25µF cathode, 100k plates), a 12AX7 gain stage plus a DC-coupled cathode follower feeding the SPLIT treble/bass tone network (250p into the 1M treble pot with .01 to ground at its far end; .1-200 into a 220k/100k chain injected at the 1M bass pot's WIPER with .005 and direct grounds on its ends; 220k back to the output node = the PI grid, no coupler; 4.7M NFB returned to the coupler node), a 12AX7 driver (100k plate, 1.5k cathode at +1.7 V) DC-fed from the network and coupled by .02-600 into a split-load cathodyne (56k plate, 1.5k+56k cathode, 1M grid leak to the junction; .1-400 plate and .1-200 cathode couplers into 1.5k stoppers), a 6L6G pair fixed-biased at -40 V through 220k leaks, 56k speaker NFB + 5k presence with .1-200 on the driver cathode, and a 5U4G rectifier; rails +415/+410/+332/+280, PT 8087, OT 45216, choke 14684. Not reproduced here; archived at EL34World",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_super_5f4.pdf"
      }
    ],
    "verification": {
      "status": "verified",
      "date": "2026-08-03T00:00:00.000Z",
      "max_deviation_pct": 13.1
    },
    "contributors": [
      "TheAnalogMaker"
    ]
  },
  "parts": {
    "notes": "Both pages draw four input jacks, two per channel, each with its own 68 kΩ stopper into the channel's grid, and hang the channel's 1 MΩ leak from jack 1's tip, jack side of its stopper; jack 2's contact rests on jack 1's tip. The output-transformer centre tap takes the choke's output (+410 V) with the screens, on both pages. Output tubes are drawn '6L6G' on the C-EG sheet; Fender shipped the tweed Super with 5881s (interchangeable 6L6-family) and the 5881 SPICE model stands in for simulation. The tone network is capacitor-isolated and omitted from the DC netlist (the phase-inverter grid's DC path through it is modelled as a single leak resistor). The negative-feedback resistor, the presence pot and its 0.1 µF bleed cap are chassis wiring rather than board wiring, but the drawing carries all three, so they carry designators (RNF, VR6, C17) and are drawn on the schematic. Parts drawn only as annotations (bright cap, line caps, power transformer) are listed without designators.",
    "items": [
      {
        "ref": "R1s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-1 grid stopper (jack 1)"
      },
      {
        "ref": "R3s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-1 grid stopper (jack 2)"
      },
      {
        "ref": "R2s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-2 grid stopper (jack 1)"
      },
      {
        "ref": "R4s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Channel-2 grid stopper (jack 2)"
      },
      {
        "ref": "RG1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Channel-1 input leak, jack 1's tip to ground (the grid returns through R1s)"
      },
      {
        "ref": "RG2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Channel-2 input leak, jack 1's tip to ground (the grid returns through R2s)"
      },
      {
        "ref": "RL1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1A plate load"
      },
      {
        "ref": "RL2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1B plate load"
      },
      {
        "ref": "RK1",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "Shared 12AY7 cathode bias"
      },
      {
        "ref": "C3",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Shared 12AY7 cathode bypass"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 600 V",
        "role": "V1A → channel-1 volume"
      },
      {
        "ref": "C2",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 600 V",
        "role": "V1B → channel-2 volume"
      },
      {
        "ref": "VR1",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Channel-1 volume (100 pF bright cap across it)"
      },
      {
        "ref": "VR2",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Channel-2 volume"
      },
      {
        "ref": "RM1",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel-1 mixer"
      },
      {
        "ref": "RM2",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Channel-2 mixer"
      },
      {
        "ref": "RL3",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V2A plate load"
      },
      {
        "ref": "RK2",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V2A cathode bias"
      },
      {
        "ref": "C4",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V2A cathode bypass"
      },
      {
        "ref": "RKCF",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Cathode-follower load"
      },
      {
        "ref": "RF1",
        "part": "Carbon comp resistor",
        "value": "4.7 MΩ · ½ W",
        "role": "V2A grid reference / feedback, returned to the tone network's bass-branch node"
      },
      {
        "ref": "RSL",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Tone network — bass-branch series resistor, coupler node → the bass pot's wiper"
      },
      {
        "ref": "C5",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Tone network — treble capacitor"
      },
      {
        "ref": "VR3",
        "part": "Potentiometer (taper not marked on the drawing)",
        "value": "1 MΩ",
        "role": "Treble"
      },
      {
        "ref": "C6",
        "part": "Film capacitor",
        "value": "0.01 µF · 600 V",
        "role": "Tone network — treble-pot cold end to ground"
      },
      {
        "ref": "C7",
        "part": "Film capacitor",
        "value": "0.005 µF · 600 V",
        "role": "Tone network — bass-pot leg capacitor to ground"
      },
      {
        "ref": "C16",
        "part": "Film capacitor",
        "value": "0.1 µF · 200 V",
        "role": "Tone network — bass-branch coupling capacitor"
      },
      {
        "ref": "RSH",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Tone network — bass-branch leak to ground"
      },
      {
        "ref": "RSR",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Tone network — bass branch into the stack output (the phase-inverter grid)"
      },
      {
        "ref": "VR4",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Bass (the network injects at its wiper)"
      },
      {
        "ref": "RLA",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V3A (driver) plate load"
      },
      {
        "ref": "RK3",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V3A cathode bias (the 56 kΩ NFB and the presence network land here)"
      },
      {
        "ref": "C8",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 600 V",
        "role": "Driver plate → cathodyne grid"
      },
      {
        "ref": "RGB",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Cathodyne grid leak, returned to the 1.5 kΩ/56 kΩ cathode junction"
      },
      {
        "ref": "RLB",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "V3B (cathodyne) plate load"
      },
      {
        "ref": "RKA",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "Cathodyne cathode resistor (cathode → the 56 kΩ junction)"
      },
      {
        "ref": "RKB",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Cathodyne cathode load (junction → ground)"
      },
      {
        "ref": "RNF",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Negative feedback, speaker → V3A (driver) cathode"
      },
      {
        "ref": "VR6",
        "part": "Linear potentiometer",
        "value": "5 kΩ",
        "role": "Presence — a rheostat from the driver's cathode into C17: the schematic leaves its far end open and the layout page straps it to the wiper; nothing grounds the track"
      },
      {
        "ref": "C17",
        "part": "Film capacitor",
        "value": "0.1 µF · 200 V",
        "role": "Presence wiper to ground"
      },
      {
        "ref": "C9",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 400 V",
        "role": "Cathodyne plate → V4 grid"
      },
      {
        "ref": "C10",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 200 V",
        "role": "Cathodyne cathode → V5 grid"
      },
      {
        "ref": "R5s",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V4 grid stopper"
      },
      {
        "ref": "R6s",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V5 grid stopper"
      },
      {
        "ref": "RGL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "V4 grid leak, from the −40 V bias line"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "V5 grid leak, from the −40 V bias line"
      },
      {
        "ref": "RD1",
        "part": "Power resistor",
        "value": "10 kΩ",
        "role": "Rail dropper B+2 → B+3"
      },
      {
        "ref": "RD2",
        "part": "Power resistor",
        "value": "10 kΩ",
        "role": "Rail dropper B+3 → B+4"
      },
      {
        "ref": "L1",
        "part": "Filter choke",
        "value": "Fender 14684",
        "role": "B+1 → B+2 (screens and output-transformer centre tap)"
      },
      {
        "ref": "C11",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Filter, B+1 (reservoir, the choke's input)"
      },
      {
        "ref": "C12",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Filter, B+2 (screens and output-transformer centre tap)"
      },
      {
        "ref": "C13",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Filter, B+3"
      },
      {
        "ref": "C14",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 450 V",
        "role": "Filter, B+4"
      },
      {
        "ref": "D1",
        "part": "Rectifier (bias)",
        "value": "selenium (silicon diode in modern builds)",
        "role": "Bias supply rectifier"
      },
      {
        "ref": "RB1",
        "part": "Carbon comp resistor",
        "value": "6.8 kΩ · ½ W",
        "role": "Bias supply series resistor"
      },
      {
        "ref": "RB2",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Bias supply bleeder"
      },
      {
        "ref": "C15",
        "part": "Electrolytic capacitor",
        "value": "100 µF · 25 V",
        "role": "Bias supply filter, −40 V line to ground (the layout page prints \"100 MFD. 25 VOLTS\"; the schematic gives it no value)"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "12AY7",
        "role": "Both input stages (V1A/V1B)"
      },
      {
        "ref": "V2",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Gain stage + cathode follower (V2A/V2B)"
      },
      {
        "ref": "V3",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Phase-inverter driver + split-load cathodyne (V3A/V3B)"
      },
      {
        "ref": "V4",
        "part": "Power tube",
        "value": "6L6G",
        "role": "Push-pull output (upper)"
      },
      {
        "ref": "V5",
        "part": "Power tube",
        "value": "6L6G",
        "role": "Push-pull output (lower)"
      },
      {
        "ref": "V6",
        "part": "Rectifier tube",
        "value": "5U4G",
        "role": "Full-wave rectifier (V6A/V6B)"
      },
      {
        "ref": "T1",
        "part": "Power transformer",
        "value": "Fender 8087",
        "role": "HT winding with a centre tap and a bias tap between one end and the centre tap (the layout letters that lead red-blue), 5 V rectifier-filament and 6.3 V heater windings; the bias rectifier is fed from the tap, not from a rectifier plate"
      },
      {
        "ref": "T3",
        "part": "Output transformer",
        "value": "Fender 45216",
        "role": "Push-pull output into 2 × 10 in speakers"
      },
      {
        "ref": "—",
        "part": "Mica capacitor",
        "value": "100 pF",
        "role": "Bright cap across VR1 (annotation only on schematic)"
      },
      {
        "ref": "—",
        "part": "Film capacitor",
        "value": "0.05 µF · 600 V (×2)",
        "role": "One at the ground switch (AC line), one from the 5U4G's output — the standby switch's rectifier side — to ground (annotation only)"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Fender 5F4 (C-EG) drawing, printed voltages: rails +415/+410/+332/+280, bias -40; 12AY7 plates +140, cathode +2.2; V2A plate +140, cathode +2.2, cathode-follower +140; PI driver plate +213 with +1.7 cathode; cathodyne plate +270, cathode +55, 1.5k/56k junction +53.3",
    "nodes": {
      "BP2": {
        "chart": 410,
        "tol_pct": 8,
        "note": "screens and output-transformer centre tap, after the choke — both pages put the centre tap here (schematic: into the screen line; layout: the OT's RED lead on a 6L6G screen pin). The printed 415 → 410 drop is taken by the full plate + screen current; this netlist omits output-transformer primary DCR, so the plates sit on this node too. The choke's DCR is entered at a 130 Ω estimate, not fitted."
      },
      "BP3": {
        "chart": 332,
        "tol_pct": 8,
        "note": "PI supply node after the first 10 kΩ dropper"
      },
      "BP4": {
        "chart": 280,
        "tol_pct": 8,
        "note": "preamp node after the second 10 kΩ dropper"
      },
      "PAY1": {
        "chart": 140,
        "tol_pct": 20,
        "note": "12AY7 plate (channel 1)"
      },
      "PAY2": {
        "chart": 140,
        "tol_pct": 20,
        "note": "12AY7 plate (channel 2)"
      },
      "KAY": {
        "chart": 2.2,
        "tol_pct": 20,
        "note": "shared 12AY7 cathode, 820 Ω"
      },
      "P2A": {
        "chart": 140,
        "tol_pct": 20,
        "disputed": true,
        "dispute_note": "The printed pair (140 V plate, 2.2 V cathode) is physically impossible for a 12AX7: 2.2 V across 1.5 kΩ implies 1.47 mA, which at Vg ≈ −2.2 V requires roughly 280 V plate-to-cathode — twice the printed value. Philips' measured resistance-coupled tables put the self-consistent point near 190 V; this simulation lands near 178 V (183 V until the 2026-10-03 fix moved the output-transformer centre tap after the choke). The dispute rests on the tube's curves, not on the rail, so the fix leaves it standing."
      },
      "K2A": {
        "chart": 2.2,
        "tol_pct": 20,
        "disputed": true,
        "dispute_note": "Half of the physically-impossible printed pair on V2A — see P2A."
      },
      "KCF": {
        "chart": 140,
        "tol_pct": 20,
        "disputed": true,
        "dispute_note": "Direct-coupled to V2A's plate, so it inherits the disputed printed 140 V; simulation follows the self-consistent operating point, near 178 V."
      },
      "PPIA": {
        "chart": 213,
        "tol_pct": 20,
        "note": "V3A (driver) plate, 100 kΩ load — consistent with the printed +1.7 V cathode: ≈1.2 mA through both"
      },
      "KPIA": {
        "chart": 1.7,
        "tol_pct": 20,
        "note": "V3A cathode, 1.5 kΩ (printed beside the tube; the NFB/presence network landing here is DC-neutral to within a few percent)"
      },
      "PPIB": {
        "chart": 270,
        "tol_pct": 20,
        "note": "V3B (cathodyne) plate, 56 kΩ load"
      },
      "KPI": {
        "chart": 55,
        "tol_pct": 20,
        "note": "V3B cathode, 1.5 kΩ above the 56 kΩ leg — the printed 55/53.3 pair implies the same ≈1 mA the plate figure does"
      },
      "JPI": {
        "chart": 53.3,
        "tol_pct": 20,
        "note": "1.5 kΩ/56 kΩ junction — the cathodyne grid's DC reference through the 1 MΩ leak"
      },
      "G51": {
        "chart": -40,
        "tol_pct": 8,
        "note": "6L6G fixed bias via 220k from the -40 V supply"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BP2",
      "chart": 410,
      "sim": 401.976,
      "disputed": false,
      "dev_pct": 1.9570731707317073,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "screens and output-transformer centre tap, after the choke — both pages put the centre tap here (schematic: into the screen line; layout: the OT's RED lead on a 6L6G screen pin). The printed 415 → 410 drop is taken by the full plate + screen current; this netlist omits output-transformer primary DCR, so the plates sit on this node too. The choke's DCR is entered at a 130 Ω estimate, not fitted.",
      "dispute_note": ""
    },
    {
      "node": "BP3",
      "chart": 332,
      "sim": 326.388,
      "disputed": false,
      "dev_pct": 1.6903614457831395,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "PI supply node after the first 10 kΩ dropper",
      "dispute_note": ""
    },
    {
      "node": "BP4",
      "chart": 280,
      "sim": 272.737,
      "disputed": false,
      "dev_pct": 2.593928571428563,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "preamp node after the second 10 kΩ dropper",
      "dispute_note": ""
    },
    {
      "node": "PAY1",
      "chart": 140,
      "sim": 140.692,
      "disputed": false,
      "dev_pct": 0.4942857142857195,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AY7 plate (channel 1)",
      "dispute_note": ""
    },
    {
      "node": "PAY2",
      "chart": 140,
      "sim": 140.692,
      "disputed": false,
      "dev_pct": 0.4942857142857195,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AY7 plate (channel 2)",
      "dispute_note": ""
    },
    {
      "node": "KAY",
      "chart": 2.2,
      "sim": 2.166,
      "disputed": false,
      "dev_pct": 1.5454545454545567,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "shared 12AY7 cathode, 820 Ω",
      "dispute_note": ""
    },
    {
      "node": "P2A",
      "chart": 140,
      "sim": 177.999,
      "disputed": true,
      "dev_pct": 27.142142857142854,
      "tol_pct": 20,
      "gated": false,
      "within": null,
      "note": "",
      "dispute_note": "The printed pair (140 V plate, 2.2 V cathode) is physically impossible for a 12AX7: 2.2 V across 1.5 kΩ implies 1.47 mA, which at Vg ≈ −2.2 V requires roughly 280 V plate-to-cathode — twice the printed value. Philips' measured resistance-coupled tables put the self-consistent point near 190 V; this simulation lands near 178 V (183 V until the 2026-10-03 fix moved the output-transformer centre tap after the choke). The dispute rests on the tube's curves, not on the rail, so the fix leaves it standing."
    },
    {
      "node": "K2A",
      "chart": 2.2,
      "sim": 1.421,
      "disputed": true,
      "dev_pct": 35.409090909090914,
      "tol_pct": 20,
      "gated": false,
      "within": null,
      "note": "",
      "dispute_note": "Half of the physically-impossible printed pair on V2A — see P2A."
    },
    {
      "node": "KCF",
      "chart": 140,
      "sim": 177.687,
      "disputed": true,
      "dev_pct": 26.919285714285724,
      "tol_pct": 20,
      "gated": false,
      "within": null,
      "note": "",
      "dispute_note": "Direct-coupled to V2A's plate, so it inherits the disputed printed 140 V; simulation follows the self-consistent operating point, near 178 V."
    },
    {
      "node": "PPIA",
      "chart": 213,
      "sim": 214.644,
      "disputed": false,
      "dev_pct": 0.7718309859154955,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V3A (driver) plate, 100 kΩ load — consistent with the printed +1.7 V cathode: ≈1.2 mA through both",
      "dispute_note": ""
    },
    {
      "node": "KPIA",
      "chart": 1.7,
      "sim": 1.676,
      "disputed": false,
      "dev_pct": 1.4117647058823541,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V3A cathode, 1.5 kΩ (printed beside the tube; the NFB/presence network landing here is DC-neutral to within a few percent)",
      "dispute_note": ""
    },
    {
      "node": "PPIB",
      "chart": 270,
      "sim": 266.117,
      "disputed": false,
      "dev_pct": 1.4381481481481413,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V3B (cathodyne) plate, 56 kΩ load",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": 55,
      "sim": 61.885,
      "disputed": false,
      "dev_pct": 12.518181818181814,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V3B cathode, 1.5 kΩ above the 56 kΩ leg — the printed 55/53.3 pair implies the same ≈1 mA the plate figure does",
      "dispute_note": ""
    },
    {
      "node": "JPI",
      "chart": 53.3,
      "sim": 60.271,
      "disputed": false,
      "dev_pct": 13.078799249530965,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "1.5 kΩ/56 kΩ junction — the cathodyne grid's DC reference through the 1 MΩ leak",
      "dispute_note": ""
    },
    {
      "node": "G51",
      "chart": -40,
      "sim": -40,
      "disputed": false,
      "dev_pct": 0,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "6L6G fixed bias via 220k from the -40 V supply",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Verified",
      "summary": "12 reference nodes are within tolerance. Maintainer verification is recorded for 2026-08-03; 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.",
        "3 disputed nodes are excluded from the tolerance result; their reasoning is listed in the operating-point table.",
        "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": "7 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": "5f4-bias-presence-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "5f4"
      ],
      "title": "5F4 bias filter capacitor and presence control",
      "description": "The bias filter capacitor is listed as the layout drawing letters it, 100 µF at 25 V; it had been listed as 8 µF at 150 V. The presence control's far end is no longer grounded; the factory leaves it open on the schematic and ties it to the wiper on the layout. No operating point changes.",
      "commit": "06efbd5cea4c7b0238741c22d82a615432e3232d",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/06efbd5cea4c7b0238741c22d82a615432e3232d"
    },
    {
      "id": "5f4-ot-centre-tap-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "5f4"
      ],
      "title": "5F4 output-transformer centre tap and input stoppers",
      "description": "The output transformer's centre tap now takes the supply node after the choke, with the screens, as both factory pages draw it. It had been connected to the reservoir side of the choke. The corrected operating point remains within the published chart tolerances. Each of the four input jacks now has its own 68 kΩ grid stopper, as both pages show; the parts list had carried two.",
      "commit": "a085257d2e8535dcf71eaa017dda3a2c39b5c38f",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/a085257d2e8535dcf71eaa017dda3a2c39b5c38f"
    }
  ],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/5f4"
}