{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "5f6a",
  "url": "https://circuitcodex.com/amps/5f6a/",
  "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": "5f6a",
    "name_style": "Tweed Bassman-style",
    "family": "tweed",
    "era": {
      "start": 1958,
      "end": 1960
    },
    "wattage": 40,
    "tubes": [
      "12AY7",
      "12AX7",
      "12AX7",
      5881,
      5881,
      "GZ34"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "GZ34"
      },
      "bias": "fixed",
      "phase_inverter": "long-tailed-pair",
      "tone_stack": "cathode-follower-fmv"
    },
    "lineage": {
      "derived_from": [
        "5f6"
      ],
      "influenced": [
        "jtm45"
      ]
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "Fender 'Bassman' Model 5F6-A drawing (I-EG): every component value AND the printed voltage chart read directly from the published schematic (2026-07-18; tone-stack nodes re-read at lug level 2026-08-03 — the sheet draws the 5F6's ladder: 250p and 56k both off the CF node, first 0.02 to the treble-lug/bass node, bass rheostat, second 0.02 into the middle pot's wiper, treble-wiper output, middle foot grounded) (+432/+430/+385/+325 rails, -48 V bias, tube pins; PI = 82k/100k 5% plates, 470R+10k tail, 1M leaks to the junction; 470R-1W screen resistors; PT 8087 325-0-325, choke 14684, OT 45249). Not reproduced here; archived at EL34World",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_bassman_5f6a.pdf"
      },
      {
        "desc": "Rob Robinette, 5F6A modifications page — cross-reference; note its '6.8k stock PI tail' claim is corrected by the I-EG drawing (10k printed)",
        "url": "https://robrobinette.com/5F6A_Modifications.htm"
      },
      {
        "desc": "Fender 'Bassman' 5F6-A layout drawing (I-EG), page 1 — the source for the board-layout drawing on this page: the order in which parts sit on the eyelet board AND the wiring layer (which eyelet each lead leaves, where it lands on the sockets/pots/jacks/transformers, and the marked lead colours — PT red/red-yellow/yellow HT + rectifier-filament, red-blue bias; OT blue/brown plate + red centre-tap + black/green secondary). The chassis-only PT primary (black) and 6.3 V heater (green) leads are not drawn. Redrawn from the published facts, never traced",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_bassman_5f6a.pdf"
      }
    ],
    "verification": {
      "status": "verified",
      "date": "2026-07-18T00:00:00.000Z",
      "max_deviation_pct": 9.8
    },
    "contributors": [
      "TheAnalogMaker"
    ]
  },
  "parts": {
    "notes": "Both pages draw four input jacks, two per channel, each with its own 68 kΩ stopper (R1s/R3s Bright, R2s/R4s Normal), and hang each channel's 1 MΩ leak from jack 1's tip; jack 2's contact rests on jack 1's tip. The presence pot and its 0.1 µF wiper cap are chassis wiring, and the negative-feedback resistor mounts on the eyelet board beside the tail's 10 kΩ, as the factory layout places it. They are this revision's headline change from the 5F6, so all three carry designators (RNF, VR6, C16) and are drawn on the schematic. Parts drawn only as annotations (bright cap, balance cap) are listed without designators.",
    "items": [
      {
        "ref": "R1s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Bright-channel grid stopper (jack 1)"
      },
      {
        "ref": "R3s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Bright-channel grid stopper (jack 2)"
      },
      {
        "ref": "R2s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Normal-channel grid stopper (jack 1)"
      },
      {
        "ref": "R4s",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Normal-channel grid stopper (jack 2)"
      },
      {
        "ref": "RG1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Bright input grid leak"
      },
      {
        "ref": "RG2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Normal input grid leak"
      },
      {
        "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": "250 µF · 6 V",
        "role": "Shared 12AY7 cathode bypass"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 400 V",
        "role": "V1A → bright volume"
      },
      {
        "ref": "C2",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 400 V",
        "role": "V1B → normal volume"
      },
      {
        "ref": "VR1",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Bright volume (100 pF bright cap across it)"
      },
      {
        "ref": "VR2",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Normal volume"
      },
      {
        "ref": "RM1",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Bright-channel mixer"
      },
      {
        "ref": "RM2",
        "part": "Carbon comp resistor",
        "value": "270 kΩ · ½ W",
        "role": "Normal-channel mixer"
      },
      {
        "ref": "RL3",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V2A plate load"
      },
      {
        "ref": "RK2",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "V2A cathode bias"
      },
      {
        "ref": "RKCF",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Cathode-follower load"
      },
      {
        "ref": "RSL",
        "part": "Carbon comp resistor",
        "value": "56 kΩ · ½ W",
        "role": "Tone-stack slope resistor"
      },
      {
        "ref": "C4",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Tone stack — treble"
      },
      {
        "ref": "VR3",
        "part": "Linear potentiometer",
        "value": "250 kΩ",
        "role": "Treble (the factory layout page marks it 250K LIN.)"
      },
      {
        "ref": "C5",
        "part": "Film capacitor",
        "value": "0.02 µF · 400 V",
        "role": "Tone stack — bass (the parts list prints one 0.02 µF line covering both this and the middle position)"
      },
      {
        "ref": "C5b",
        "part": "Film capacitor",
        "value": "0.02 µF · 400 V",
        "role": "Tone stack — middle (same printed line as C5)"
      },
      {
        "ref": "VR4",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ",
        "role": "Bass"
      },
      {
        "ref": "VR5",
        "part": "Linear potentiometer",
        "value": "25 kΩ",
        "role": "Middle (the second 0.02 µF lands on its wiper; its full track stands in the ground leg)"
      },
      {
        "ref": "C6",
        "part": "Coupling capacitor",
        "value": "0.02 µF · 400 V",
        "role": "Tone stack → phase-inverter grid"
      },
      {
        "ref": "RGA",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (V3A), returned to tail junction"
      },
      {
        "ref": "RGB",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (V3B), returned to tail junction"
      },
      {
        "ref": "RLA",
        "part": "Carbon comp resistor",
        "value": "82 kΩ · ½ W · 5%",
        "role": "PI plate load (V3A)"
      },
      {
        "ref": "RLB",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W · 5%",
        "role": "PI plate load (V3B)"
      },
      {
        "ref": "RTAIL",
        "part": "Carbon comp resistor",
        "value": "470 Ω · ½ W",
        "role": "PI tail bias"
      },
      {
        "ref": "RT2",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "PI tail (junction → foot)"
      },
      {
        "ref": "RNF",
        "part": "Carbon comp resistor",
        "value": "27 kΩ · ½ W",
        "role": "Negative feedback, speaker → the foot of the phase-inverter tail"
      },
      {
        "ref": "VR6",
        "part": "Linear potentiometer",
        "value": "5 kΩ",
        "role": "Presence — its track from the tail's foot to ground, 0.1 µF on the wiper; the 5F6 puts the same pot in the tone stack's ground leg instead"
      },
      {
        "ref": "C16",
        "part": "Film capacitor",
        "value": "0.1 µF · 200 V",
        "role": "Presence wiper to ground"
      },
      {
        "ref": "C7",
        "part": "Film capacitor",
        "value": "0.1 µF · 200 V",
        "role": "V3B grid AC ground, to the tail's foot"
      },
      {
        "ref": "C8",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 400 V",
        "role": "PI → V4 grid"
      },
      {
        "ref": "C9",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 400 V",
        "role": "PI → V5 grid"
      },
      {
        "ref": "RGL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "V4 grid leak, from the −48 V bias line"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "V5 grid leak, from the −48 V bias line"
      },
      {
        "ref": "RS1",
        "part": "Carbon comp resistor",
        "value": "470 Ω · 1 W",
        "role": "V4 screen resistor"
      },
      {
        "ref": "RS2",
        "part": "Carbon comp resistor",
        "value": "470 Ω · 1 W",
        "role": "V5 screen resistor"
      },
      {
        "ref": "RD1",
        "part": "Power resistor",
        "value": "4.7 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)"
      },
      {
        "ref": "C11",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter, B+1"
      },
      {
        "ref": "C11b",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter, B+1 — the I-EG schematic's second 20-600 can on the +432 V node, in parallel with C11"
      },
      {
        "ref": "C12",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 V",
        "role": "Filter, B+2"
      },
      {
        "ref": "C13",
        "part": "Electrolytic capacitor",
        "value": "20 µF · 600 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": "15 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": "8 µF · 150 V",
        "role": "Bias supply filter, −48 V line"
      },
      {
        "ref": "C15b",
        "part": "Electrolytic capacitor",
        "value": "8 µF · 150 V",
        "role": "Bias supply reservoir, rectifier side of the 15 kΩ (the sheet's second can — the parts list prints one 8 µF · 150 V line covering both)"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "12AY7",
        "role": "Both input stages (V1A/V1B)"
      },
      {
        "ref": "V2",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Second stage + cathode follower (V2A/V2B)"
      },
      {
        "ref": "V3",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Long-tailed-pair phase inverter (V3A/V3B)"
      },
      {
        "ref": "V4",
        "part": "Power tube",
        "value": "5881",
        "role": "Push-pull output (upper)"
      },
      {
        "ref": "V5",
        "part": "Power tube",
        "value": "5881",
        "role": "Push-pull output (lower)"
      },
      {
        "ref": "V6",
        "part": "Rectifier tube",
        "value": "GZ34",
        "role": "Full-wave rectifier (V6A/V6B)"
      },
      {
        "ref": "T3",
        "part": "Output transformer",
        "value": "Fender 45249 · 2 Ω secondary",
        "role": "Push-pull output into four 8 Ω speakers"
      },
      {
        "ref": "—",
        "part": "Power transformer",
        "value": "Fender 8087 · 325-0-325 V",
        "role": "HT + heaters + rectifier filament"
      },
      {
        "ref": "—",
        "part": "Mica capacitor",
        "value": "100 pF",
        "role": "Bright cap across VR1 (annotation only on schematic)"
      },
      {
        "ref": "—",
        "part": "Mica capacitor",
        "value": "47 pF",
        "role": "Across the two PI plates (annotation only)"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Fender 5F6-A (I-EG) drawing, printed voltages: rails +432/+430/+385/+325, bias -48; pins 12AY7 +150/+2.5, V2A +180/+1.2? (printed near cathode), CF +180, PI plates +235/+230, PI cathodes +34, tail junction +32.5",
    "nodes": {
      "BP2": {
        "chart": 430,
        "tol_pct": 8,
        "note": "screens node after choke (DCR estimated at 130 Ω)"
      },
      "BP3": {
        "chart": 385,
        "tol_pct": 8,
        "note": "PI supply node after 4.7 kΩ"
      },
      "BP4": {
        "chart": 325,
        "tol_pct": 8,
        "note": "preamp node after the 10 kΩ dropper"
      },
      "PAY1": {
        "chart": 150,
        "tol_pct": 20,
        "note": "12AY7 plate, printed pin value"
      },
      "PAY2": {
        "chart": 150,
        "tol_pct": 20,
        "note": "12AY7 plate (normal channel)"
      },
      "KAY": {
        "chart": 2.5,
        "tol_pct": 20,
        "note": "shared 12AY7 cathode, 820 Ω"
      },
      "P2A": {
        "chart": 180,
        "tol_pct": 20,
        "note": "V2A plate = CF grid (direct-coupled)"
      },
      "KCF": {
        "chart": 180,
        "tol_pct": 20,
        "note": "cathode follower output, printed +180"
      },
      "PPIA": {
        "chart": 235,
        "tol_pct": 20,
        "note": "PI plate, 82k 5% side"
      },
      "PPIB": {
        "chart": 230,
        "tol_pct": 20,
        "note": "PI plate, 100k 5% side"
      },
      "KPI": {
        "chart": 34,
        "tol_pct": 20,
        "disputed": true,
        "dispute_note": "The printed tail figures fit a tail the drawing does not show. The printed plates (+235 V through 82 kΩ and +230 V through 100 kΩ, both off +385 V) carry 1.83 + 1.55 = 3.38 mA, and 3.38 mA through a 10 kΩ returned straight to ground is 33.8 V at the junction and 35.4 V at these cathodes — the printed +32.5 V and +34 V. But the I-EG schematic and layout both land that 10 kΩ on a node of its own, returned to ground through the 27 kΩ feedback resistor and the 5 kΩ presence pot's track in parallel (4.2 kΩ); at the same 3.38 mA that puts the junction at 48.0 V and these cathodes at 49.6 V. The chart is also, figure for figure, the one the 5F6 (F-EG) prints — rails, bias, every pin, down to the +22/+23 V grids — and the 5F6's 10 kΩ does return to ground. Simulation follows the drawn tail."
      },
      "JPI": {
        "chart": 32.5,
        "tol_pct": 20,
        "disputed": true,
        "dispute_note": "The other half of the same contradiction — see KPI. The printed plates' 3.38 mA through the 10 kΩ alone gives 33.8 V, which fits the printed +32.5 V only if the 10 kΩ returns to ground; through the drawn foot (27 kΩ ∥ 5 kΩ = 4.2 kΩ) the same current puts the junction at 48.0 V."
      },
      "PRES": {
        "chart": null,
        "note": "informational — the tail's foot, where the 10 kΩ, the 27 kΩ feedback resistor, the presence pot's track and the V3B grid's 0.1 µF meet; the drawing prints no figure here"
      },
      "S51": {
        "chart": null,
        "note": "informational — 5881 screen after 470 Ω"
      },
      "G51": {
        "chart": -48,
        "tol_pct": 8,
        "note": "fixed bias via 220k from the -48 V supply"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "BP2",
      "chart": 430,
      "sim": 430.531,
      "disputed": false,
      "dev_pct": 0.12348837209302463,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "screens node after choke (DCR estimated at 130 Ω)",
      "dispute_note": ""
    },
    {
      "node": "BP3",
      "chart": 385,
      "sim": 386.508,
      "disputed": false,
      "dev_pct": 0.39168831168830687,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "PI supply node after 4.7 kΩ",
      "dispute_note": ""
    },
    {
      "node": "BP4",
      "chart": 325,
      "sim": 322.609,
      "disputed": false,
      "dev_pct": 0.7356923076923136,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "preamp node after the 10 kΩ dropper",
      "dispute_note": ""
    },
    {
      "node": "PAY1",
      "chart": 150,
      "sim": 164.627,
      "disputed": false,
      "dev_pct": 9.75133333333334,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AY7 plate, printed pin value",
      "dispute_note": ""
    },
    {
      "node": "PAY2",
      "chart": 150,
      "sim": 164.627,
      "disputed": false,
      "dev_pct": 9.75133333333334,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "12AY7 plate (normal channel)",
      "dispute_note": ""
    },
    {
      "node": "KAY",
      "chart": 2.5,
      "sim": 2.591,
      "disputed": false,
      "dev_pct": 3.6400000000000077,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "shared 12AY7 cathode, 820 Ω",
      "dispute_note": ""
    },
    {
      "node": "P2A",
      "chart": 180,
      "sim": 181.802,
      "disputed": false,
      "dev_pct": 1.001111111111107,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "V2A plate = CF grid (direct-coupled)",
      "dispute_note": ""
    },
    {
      "node": "KCF",
      "chart": 180,
      "sim": 182.221,
      "disputed": false,
      "dev_pct": 1.233888888888891,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "cathode follower output, printed +180",
      "dispute_note": ""
    },
    {
      "node": "PPIA",
      "chart": 235,
      "sim": 256.965,
      "disputed": false,
      "dev_pct": 9.346808510638287,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "PI plate, 82k 5% side",
      "dispute_note": ""
    },
    {
      "node": "PPIB",
      "chart": 230,
      "sim": 246.801,
      "disputed": false,
      "dev_pct": 7.304782608695646,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "PI plate, 100k 5% side",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": 34,
      "sim": 43.726,
      "disputed": true,
      "dev_pct": 28.605882352941176,
      "tol_pct": 20,
      "gated": false,
      "within": null,
      "note": "",
      "dispute_note": "The printed tail figures fit a tail the drawing does not show. The printed plates (+235 V through 82 kΩ and +230 V through 100 kΩ, both off +385 V) carry 1.83 + 1.55 = 3.38 mA, and 3.38 mA through a 10 kΩ returned straight to ground is 33.8 V at the junction and 35.4 V at these cathodes — the printed +32.5 V and +34 V. But the I-EG schematic and layout both land that 10 kΩ on a node of its own, returned to ground through the 27 kΩ feedback resistor and the 5 kΩ presence pot's track in parallel (4.2 kΩ); at the same 3.38 mA that puts the junction at 48.0 V and these cathodes at 49.6 V. The chart is also, figure for figure, the one the 5F6 (F-EG) prints — rails, bias, every pin, down to the +22/+23 V grids — and the 5F6's 10 kΩ does return to ground. Simulation follows the drawn tail."
    },
    {
      "node": "JPI",
      "chart": 32.5,
      "sim": 42.327,
      "disputed": true,
      "dev_pct": 30.236923076923073,
      "tol_pct": 20,
      "gated": false,
      "within": null,
      "note": "",
      "dispute_note": "The other half of the same contradiction — see KPI. The printed plates' 3.38 mA through the 10 kΩ alone gives 33.8 V, which fits the printed +32.5 V only if the 10 kΩ returns to ground; through the drawn foot (27 kΩ ∥ 5 kΩ = 4.2 kΩ) the same current puts the junction at 48.0 V."
    },
    {
      "node": "PRES",
      "chart": null,
      "sim": 12.559,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — the tail's foot, where the 10 kΩ, the 27 kΩ feedback resistor, the presence pot's track and the V3B grid's 0.1 µF meet; the drawing prints no figure here",
      "dispute_note": ""
    },
    {
      "node": "S51",
      "chart": null,
      "sim": 430.078,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "informational — 5881 screen after 470 Ω",
      "dispute_note": ""
    },
    {
      "node": "G51",
      "chart": -48,
      "sim": -48,
      "disputed": false,
      "dev_pct": 0,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "fixed bias via 220k from the -48 V supply",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Verified",
      "summary": "11 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.",
        "2 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.",
        "3 sheet-only parts are explicitly excluded: C11b, D1, RKCF. 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": "5f6a-input-stoppers-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "5f6a"
      ],
      "title": "5F6-A input grid stoppers",
      "description": "Each of the four input jacks now has its own 68 kΩ grid stopper, as both factory pages show. The parts list, schematic and board had carried one per channel. No operating point changes.",
      "commit": "1ad5f458c09b1d9e4a7d279d8b9a0ba30bd46388",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/1ad5f458c09b1d9e4a7d279d8b9a0ba30bd46388"
    },
    {
      "id": "5f6a-reservoir-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "5f6a"
      ],
      "title": "5F6-A reservoir capacitors",
      "description": "The +432 V reservoir node carries two 20 µF capacitors in parallel, as the factory schematic draws; the second was missing. No operating point changes.",
      "commit": "bd5349f01d07584afc87037bb33672b03078ef1f",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/bd5349f01d07584afc87037bb33672b03078ef1f"
    }
  ],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/5f6a"
}