{
  "format": "circuit-codex-reference",
  "version": 1,
  "id": "ab763",
  "url": "https://circuitcodex.com/amps/ab763/",
  "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": "ab763",
    "name_style": "Blackface Deluxe Reverb-style",
    "family": "blackface",
    "era": {
      "start": 1964,
      "end": 1967
    },
    "wattage": 22,
    "tubes": [
      "12AX7",
      "12AX7",
      "12AX7",
      "12AT7",
      "12AX7",
      "12AT7",
      "6V6GT",
      "6V6GT",
      "GZ34"
    ],
    "topology": {
      "rectifier": {
        "kind": "tube",
        "type": "GZ34"
      },
      "bias": "fixed",
      "phase_inverter": "long-tailed-pair",
      "tone_stack": "tb"
    },
    "lineage": {
      "derived_from": [
        "6g3"
      ],
      "influenced": []
    },
    "conventions": {
      "designators": "functional"
    },
    "sources": [
      {
        "desc": "Fender 'Deluxe Reverb-Amp AB763' drawing (C-FD), schematic + layout: every component value AND the printed voltage chart read directly from the published sheet (+415 plates/screens, +420 OT centre tap, +410 reverb-driver plate, +325 phase-inverter plate node [C], +180/+170 preamp plates, PI +170/+180 plates with +77/+75.5 tail, +8.7 reverb-driver cathode, +1.3 preamp cathodes, -35 V fixed bias; LTP PI = 82k/100k 5% plates + 470 Ohm/22k tail with 1M leaks to the junction; 6V6 220k grid leaks + 470 Ohm-1W screens; reverb driver 12AT7 both sections paralleled into the 125A20B transformer). Notice: values +/-20%, read to ground with an electronic voltmeter. The preamp bottles are labelled 7025 (a 12AX7 alias). Tone stacks re-read at lug level 2026-08-03: BOTH channels draw the AA964's two-knob ladder (100k slope + 250p off the plate node, 0.1 to the treble-lug/bass node, bass rheostat over the 0.047/6.8k foot, treble-wiper output), and the vibrato channel's 47 pF bright cap sits across the VOLUME pot, top lug to wiper. Re-read at native size 2026-09-10 (schematic 6070 × 4274, layout 6026 × 3650): the Normal channel's volume feeds a second 7025 stage (100 kΩ plate, +180 V; .047 → 220 kΩ into the mix node, which a .001 couples into the inverter), whose cathode the sheet boxes [A] with the Vibrato second stage's — one 820 Ω / 25 µF for both; the mix driver's cathode is boxed [E] onto the reverb recovery's one 820 Ω / 25 µF the same way; all six 100 kΩ preamp plate loads return to node [D], which carries no printed voltage, and the tremolo's plate loads to [B]; on both channel bottles the layout puts the input stage on pins 1-2-3 and the second stage on 6-7-8. Not reproduced here; archived at EL34World",
        "url": "https://el34world.com/charts/Schematics/files/Fender/Fender_deluxe_reverb_ab763.pdf"
      },
      {
        "desc": "RCA 12AT7 data sheet (March 1, 1954) — tabulated Class-A1 characteristics read for the clean-room CC0 12AT7 tube model (Va=250 V, 200 Ohm cathode bias -> Ia=10 mA, gm=5500 umho, mu=60; second point Va=100 V/270 Ohm -> 3.7 mA, 4000 umho). Basing 9A. Used by the reverb driver and the phase inverter",
        "url": "https://frank.pocnet.net/sheets/049/1/12AT7.pdf"
      }
    ],
    "verification": {
      "status": "verified",
      "date": "2026-07-19T00:00:00.000Z",
      "max_deviation_pct": 13.6
    },
    "sections": {
      "V5": "excluded — the tremolo bottle: a running phase-shift oscillator and its lamp driver; neither has a static operating point, and their plate loads return to box [B], the driven node BP1, so no gated node moves"
    },
    "contributors": [
      "TheAnalogMaker"
    ]
  },
  "parts": {
    "notes": "The drawing shows both instrument jacks (1 and 2) of each channel with their normalling contacts; this sheet draws them as the two input labels, with the 1 MΩ leak at jack 1's tip, jack side of its 68 kΩ stopper, where C-FD puts it. Tremolo-oscillator and reverb-tank interconnect parts are listed but the oscillator's DC point is excluded from the netlist (see the circuit story). Two cathode networks are shared, and each is listed once, under the stage where the drawing draws it: RKV2/CKV2 carry both second stages (the drawing's boxed [A]), RKR1/CKR1 both the reverb recovery and the mix driver (boxed [E]). Neither the Normal second stage nor the mix driver has a cathode resistor of its own.",
    "items": [
      {
        "ref": "R1n",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Normal input grid stopper (jack 1)"
      },
      {
        "ref": "R2n",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Normal input grid stopper (jack 2)"
      },
      {
        "ref": "RGN1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Normal input leak, jack 1's tip to ground (jack side of R1n); the grid's DC return through R1n"
      },
      {
        "ref": "RLN1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1a plate load"
      },
      {
        "ref": "RKN1",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V1a cathode bias"
      },
      {
        "ref": "CKN1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V1a cathode bypass"
      },
      {
        "ref": "CTN",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Normal treble cap"
      },
      {
        "ref": "VRTN",
        "part": "Potentiometer",
        "value": "250 kΩ-A",
        "role": "Normal treble"
      },
      {
        "ref": "RSN",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Normal tone-stack slope resistor"
      },
      {
        "ref": "CBN",
        "part": "Coupling capacitor",
        "value": "0.1 µF",
        "role": "Normal tone-stack bass cap, slope node to the bass pot"
      },
      {
        "ref": "VRBN",
        "part": "Potentiometer",
        "value": "250 kΩ-A",
        "role": "Normal bass"
      },
      {
        "ref": "CBN2",
        "part": "Coupling capacitor",
        "value": "0.047 µF",
        "role": "Normal tone-stack middle-leg cap, slope node to the bleed resistor"
      },
      {
        "ref": "RSLN",
        "part": "Carbon comp resistor",
        "value": "6.8 kΩ · ½ W",
        "role": "Normal tone-stack bleed resistor"
      },
      {
        "ref": "VRVN",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ-A",
        "role": "Normal volume"
      },
      {
        "ref": "RLN2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V1b (normal 2nd stage) plate load"
      },
      {
        "ref": "CCN2",
        "part": "Coupling capacitor",
        "value": "0.047 µF",
        "role": "V1b output coupling, into the mixing resistor RMN2"
      },
      {
        "ref": "RMN2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Normal-channel mixing resistor, into the phase-inverter input node"
      },
      {
        "ref": "R1v",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Vibrato input grid stopper (jack 1)"
      },
      {
        "ref": "R2v",
        "part": "Carbon comp resistor",
        "value": "68 kΩ · ½ W",
        "role": "Vibrato input grid stopper (jack 2)"
      },
      {
        "ref": "RGV1",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Vibrato input leak, jack 1's tip to ground (jack side of R1v); the grid's DC return through R1v"
      },
      {
        "ref": "RLV1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V2a plate load"
      },
      {
        "ref": "RKV1",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V2a cathode bias"
      },
      {
        "ref": "CKV1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "V2a cathode bypass"
      },
      {
        "ref": "CTV",
        "part": "Mica capacitor",
        "value": "250 pF",
        "role": "Vibrato treble cap"
      },
      {
        "ref": "CBRV",
        "part": "Mica capacitor",
        "value": "47 pF",
        "role": "Vibrato bright cap, across the volume pot (top lug to wiper)"
      },
      {
        "ref": "VRTV",
        "part": "Potentiometer",
        "value": "250 kΩ-A",
        "role": "Vibrato treble"
      },
      {
        "ref": "RSV",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Vibrato tone-stack slope resistor"
      },
      {
        "ref": "CBV",
        "part": "Coupling capacitor",
        "value": "0.1 µF",
        "role": "Vibrato tone-stack bass cap, slope node to the bass pot"
      },
      {
        "ref": "VRBV",
        "part": "Potentiometer",
        "value": "250 kΩ-A",
        "role": "Vibrato bass"
      },
      {
        "ref": "CBV2",
        "part": "Coupling capacitor",
        "value": "0.047 µF",
        "role": "Vibrato tone-stack middle-leg cap, slope node to the bleed resistor"
      },
      {
        "ref": "RSLV",
        "part": "Carbon comp resistor",
        "value": "6.8 kΩ · ½ W",
        "role": "Vibrato tone-stack bleed resistor"
      },
      {
        "ref": "VRVV",
        "part": "Audio-taper potentiometer",
        "value": "1 MΩ-A",
        "role": "Vibrato volume"
      },
      {
        "ref": "RLV2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V2b (vibrato 2nd stage) plate load"
      },
      {
        "ref": "RKV2",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "Cathode bias at the drawing's boxed [A] — one resistor for BOTH second stages, Normal (V1b) and Vibrato (V2b)"
      },
      {
        "ref": "CKV2",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Cathode bypass across RKV2 (the shared [A] network)"
      },
      {
        "ref": "CCV2",
        "part": "Coupling capacitor",
        "value": "0.02 µF",
        "role": "V2b output coupling — into the reverb send (CRS) and the dry path (RGD1)"
      },
      {
        "ref": "CRS",
        "part": "Coupling capacitor",
        "value": "500 pF",
        "role": "Reverb send coupling, from the .02's far side to the driver grid"
      },
      {
        "ref": "RGRD",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Reverb-driver 12AT7 grid leak"
      },
      {
        "ref": "RKRD",
        "part": "Carbon comp resistor",
        "value": "2.2 kΩ · ½ W",
        "role": "Reverb-driver shared cathode bias"
      },
      {
        "ref": "CKRD",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Reverb-driver cathode bypass"
      },
      {
        "ref": "T4",
        "part": "Reverb transformer",
        "value": "Fender 125A20B",
        "role": "Reverb driver → tank input"
      },
      {
        "ref": "RGR1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Reverb-recovery grid return to ground, mounted at the reverb-pedal jack (the tank return lands on the grid)"
      },
      {
        "ref": "RLR1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V3b (reverb recovery) plate load"
      },
      {
        "ref": "RKR1",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "Cathode bias at the drawing's boxed [E] — one resistor for BOTH the reverb recovery (V3b) and the mix driver (V3a)"
      },
      {
        "ref": "CKR1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Cathode bypass across RKR1 (the shared [E] network)"
      },
      {
        "ref": "CCR1",
        "part": "Coupling capacitor",
        "value": "0.003 µF",
        "role": "Reverb-recovery output coupling"
      },
      {
        "ref": "VRREV",
        "part": "Linear potentiometer",
        "value": "100 kΩ-L",
        "role": "Reverb level"
      },
      {
        "ref": "RMR",
        "part": "Carbon comp resistor",
        "value": "470 kΩ · ½ W",
        "role": "Reverb mix resistor"
      },
      {
        "ref": "RLD1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "V3a (mix driver) plate load"
      },
      {
        "ref": "RGD1",
        "part": "Carbon comp resistor",
        "value": "3.3 MΩ · ½ W",
        "role": "Dry-path mixing resistor: the vibrato channel's .02 coupler → the mix-driver grid (CBD1 across it)"
      },
      {
        "ref": "RGD2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Mix-driver grid return to ground"
      },
      {
        "ref": "CBD1",
        "part": "Mica capacitor",
        "value": "10 pF",
        "role": "Bright cap across RGD1"
      },
      {
        "ref": "RMD1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Vibrato-channel mixing resistor, from the mix driver's coupler into the phase-inverter input node"
      },
      {
        "ref": "CCD1",
        "part": "Coupling capacitor",
        "value": "0.1 µF",
        "role": "Mix-driver output coupling, into the mixing resistor RMD1"
      },
      {
        "ref": "VRSPD",
        "part": "Reverse-audio potentiometer",
        "value": "3 MΩ-RA",
        "role": "Tremolo speed: a rheostat from the ladder's middle node, with RTO1 to ground"
      },
      {
        "ref": "VRINT",
        "part": "Reverse-audio potentiometer",
        "value": "50 kΩ-RA",
        "role": "Tremolo intensity: the photocell's path from the mix output to ground"
      },
      {
        "ref": "RTO1",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Speed-control series resistor, from the rheostat to ground"
      },
      {
        "ref": "RTO2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W",
        "role": "Oscillator (V5a) plate load, from the +415 V node"
      },
      {
        "ref": "RTOG",
        "part": "Carbon comp resistor",
        "value": "2.2 MΩ · ½ W",
        "role": "Return from the vibrato-pedal node to the raw negative bias supply, ahead of the 10K-L control"
      },
      {
        "ref": "RTOG2",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Vibrato-pedal node → the ladder's outer node (V5b's grid)"
      },
      {
        "ref": "RTOG3",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "Vibrato-pedal node → the oscillator grid"
      },
      {
        "ref": "RTO10",
        "part": "Carbon comp resistor",
        "value": "10 MΩ · ½ W",
        "role": "Lamp-driver (V5b) plate feed from +415 V"
      },
      {
        "ref": "RKTO1",
        "part": "Carbon comp resistor",
        "value": "2.7 kΩ · ½ W",
        "role": "Oscillator cathode bias"
      },
      {
        "ref": "RKTO2",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Lamp-driver cathode bias"
      },
      {
        "ref": "CTO1",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Phase-shift ladder: outer node → oscillator grid"
      },
      {
        "ref": "CTO2",
        "part": "Film capacitor",
        "value": "0.01 µF",
        "role": "Phase-shift ladder: middle node → outer node"
      },
      {
        "ref": "CTO3",
        "part": "Film capacitor",
        "value": "0.02 µF",
        "role": "Phase-shift ladder: oscillator plate → middle node"
      },
      {
        "ref": "CKTO1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Oscillator cathode bypass"
      },
      {
        "ref": "CKTO2",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 25 V",
        "role": "Lamp-driver cathode bypass"
      },
      {
        "ref": "RLAMP",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W",
        "role": "Neon-lamp series resistor, from +415 V"
      },
      {
        "ref": "OPTO",
        "part": "Optocoupler",
        "value": "neon lamp + photoresistor",
        "role": "Neon lamp in the lamp driver's plate feed; its photocell shunts the mix output through Intensity"
      },
      {
        "ref": "RLPA",
        "part": "Carbon comp resistor",
        "value": "82 kΩ · ½ W · 5%",
        "role": "PI plate load (hot side)"
      },
      {
        "ref": "RLPB",
        "part": "Carbon comp resistor",
        "value": "100 kΩ · ½ W · 5%",
        "role": "PI plate load (cold side)"
      },
      {
        "ref": "RGPA",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (hot), returned to tail junction"
      },
      {
        "ref": "RGPB",
        "part": "Carbon comp resistor",
        "value": "1 MΩ · ½ W",
        "role": "PI grid leak (cold), returned to tail junction"
      },
      {
        "ref": "RTAIL",
        "part": "Carbon comp resistor",
        "value": "470 Ω · ½ W",
        "role": "PI cathode resistor"
      },
      {
        "ref": "RT2",
        "part": "Carbon comp resistor",
        "value": "22 kΩ · ½ W",
        "role": "PI tail, from the junction to the feedback node (the 820/47 junction), not to ground"
      },
      {
        "ref": "CPIA",
        "part": "Coupling capacitor",
        "value": "0.001 µF",
        "role": "PI hot-grid input coupling, from the node where the two channels' 220 kΩ mixing resistors meet"
      },
      {
        "ref": "CPIB",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 200 V",
        "role": "PI cold-grid AC ground"
      },
      {
        "ref": "RNFB",
        "part": "Carbon comp resistor",
        "value": "820 Ω · ½ W",
        "role": "Negative feedback, speaker hot → the feedback node at the PI tail's foot (DC-neutral)"
      },
      {
        "ref": "RNF2",
        "part": "Carbon comp resistor",
        "value": "47 Ω · ½ W",
        "role": "Feedback node → ground: where the 820, the PI tail and the cold-grid 0.1 µF meet"
      },
      {
        "ref": "C1",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 400 V",
        "role": "PI hot plate → V7 grid"
      },
      {
        "ref": "C2",
        "part": "Coupling capacitor",
        "value": "0.1 µF · 400 V",
        "role": "PI cold plate → V8 grid"
      },
      {
        "ref": "RGL1",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W · 5%",
        "role": "V7 grid leak, from the −35 V bias line"
      },
      {
        "ref": "RGL2",
        "part": "Carbon comp resistor",
        "value": "220 kΩ · ½ W · 5%",
        "role": "V8 grid leak, from the −35 V bias line"
      },
      {
        "ref": "R7s",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V7 grid stopper, mounted on the 6V6 socket (pin 5 to the tie lug)"
      },
      {
        "ref": "R8s",
        "part": "Carbon comp resistor",
        "value": "1.5 kΩ · ½ W",
        "role": "V8 grid stopper, mounted on the 6V6 socket (pin 5 to the tie lug)"
      },
      {
        "ref": "RS1",
        "part": "Wirewound resistor",
        "value": "470 Ω · 1 W",
        "role": "V7 screen resistor"
      },
      {
        "ref": "RS2",
        "part": "Wirewound resistor",
        "value": "470 Ω · 1 W",
        "role": "V8 screen resistor"
      },
      {
        "ref": "T3",
        "part": "Output transformer",
        "value": "Fender 125A1A",
        "role": "Push-pull 6V6 output"
      },
      {
        "ref": "T1",
        "part": "Power transformer",
        "value": "Fender 125P33A · 330-0-330 V",
        "role": "HT + heaters + rectifier filament"
      },
      {
        "ref": "T2",
        "part": "Filter choke",
        "value": "Fender 125C3A",
        "role": "Reservoir → screen rail"
      },
      {
        "ref": "C10",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V (×2)",
        "role": "Reservoir filter (post-standby)"
      },
      {
        "ref": "C11",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Filter, node B (screens/+415)"
      },
      {
        "ref": "C12",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Filter, node C (+325 PI/preamp)"
      },
      {
        "ref": "C13",
        "part": "Electrolytic capacitor",
        "value": "16 µF · 450 V",
        "role": "Filter, node D (input-stage rail)"
      },
      {
        "ref": "RD1",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "Rail dropper B → C"
      },
      {
        "ref": "RD2",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "Rail dropper C → D"
      },
      {
        "ref": "RBIAS",
        "part": "Wirewound resistor",
        "value": "470 Ω · 1 W",
        "role": "Bias-supply series resistor"
      },
      {
        "ref": "DBIAS",
        "part": "Rectifier (bias)",
        "value": "silicon diode",
        "role": "Bias-supply rectifier"
      },
      {
        "ref": "CB1",
        "part": "Electrolytic capacitor",
        "value": "25 µF · 50 V",
        "role": "Bias-supply filter — the one can the C-FD drawing shows, lettered '25 / 50' (µF / V)"
      },
      {
        "ref": "VRBAL",
        "part": "Linear potentiometer",
        "value": "10 kΩ-L",
        "role": "Bias control: across the raw negative supply with RBAL; the −35 V line is its wiper"
      },
      {
        "ref": "RBAL",
        "part": "Carbon comp resistor",
        "value": "10 kΩ · ½ W",
        "role": "Bias divider leg, from the 10K-L control to ground"
      },
      {
        "ref": "CDEATH",
        "part": "Ceramic capacitor",
        "value": "0.047 µF · 600 V",
        "role": "Ground-switch cap (period; not in modern builds)"
      },
      {
        "ref": "V1",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Normal channel input + 2nd stage (V1a/V1b)"
      },
      {
        "ref": "V2",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Vibrato channel input + 2nd stage (V2a/V2b)"
      },
      {
        "ref": "V3",
        "part": "Preamp tube",
        "value": "12AX7 (7025)",
        "role": "Reverb recovery + mix driver (V3a/V3b)"
      },
      {
        "ref": "V4",
        "part": "Preamp/driver tube",
        "value": "12AT7",
        "role": "Reverb driver (both sections paralleled)"
      },
      {
        "ref": "V5",
        "part": "Preamp tube",
        "value": "12AX7",
        "role": "Tremolo oscillator + lamp driver (DC point excluded)"
      },
      {
        "ref": "V6",
        "part": "Preamp/driver tube",
        "value": "12AT7",
        "role": "Long-tailed-pair phase inverter"
      },
      {
        "ref": "V7",
        "part": "Power tube",
        "value": "6V6GT",
        "role": "Push-pull output (hot side)"
      },
      {
        "ref": "V8",
        "part": "Power tube",
        "value": "6V6GT",
        "role": "Push-pull output (cold side)"
      },
      {
        "ref": "V9",
        "part": "Rectifier tube",
        "value": "GZ34",
        "role": "Full-wave rectifier (V9A/V9B)"
      }
    ]
  },
  "publishedVoltages": {
    "source": "Fender AB763 Deluxe Reverb-Amp drawing, printed voltages: +415 (6V6 plates, screens), +420 (OT centre tap), +410 (reverb-driver plate), +345/+270 (tremolo oscillator, excluded), +325 (phase-inverter plate node [C]), +180/+170 (preamp plates), PI +170/+180 plates with +77/+75.5 tail, +8.7 (reverb-driver cathode), +1.3 (preamp cathodes; boxes [A] and [E] each printed at both ends), -35 (6V6 fixed bias)",
    "nodes": {
      "S61": {
        "chart": 415,
        "tol_pct": 8,
        "note": "6V6 (V7) screen after its 470 Ohm-1W stopper, off the +415 plate rail"
      },
      "G61": {
        "chart": -35,
        "tol_pct": 8,
        "note": "6V6 (V7) grid, fixed bias via 220k from the -35 V supply"
      },
      "PRD": {
        "chart": 410,
        "tol_pct": 20,
        "note": "reverb-driver 12AT7 plate (paralleled sections), off BP1 through the TR4 primary DCR"
      },
      "KRD": {
        "chart": 8.7,
        "tol_pct": 20,
        "note": "reverb-driver 12AT7 shared cathode over 2.2k"
      },
      "BD": {
        "chart": null,
        "note": "preamp rail, drawing node [D] — the drawing prints no voltage here; derived from the +325 V node through the 10k dropper"
      },
      "PN1": {
        "chart": 180,
        "tol_pct": 20,
        "note": "Normal-channel input plate, 100k from the preamp rail [D]"
      },
      "KN1": {
        "chart": 1.3,
        "tol_pct": 20,
        "note": "Normal-channel input cathode over 1.5k"
      },
      "PN2": {
        "chart": 180,
        "tol_pct": 20,
        "note": "Normal-channel 2nd-stage plate, 100k from the preamp rail [D]"
      },
      "PV1": {
        "chart": 170,
        "tol_pct": 20,
        "note": "Vibrato-channel input plate, 100k from the preamp rail [D]"
      },
      "KV1": {
        "chart": 1.3,
        "tol_pct": 20,
        "note": "Vibrato-channel input cathode over 1.5k"
      },
      "PV2": {
        "chart": 170,
        "tol_pct": 20,
        "note": "Vibrato-channel 2nd-stage plate, 100k from the preamp rail [D]"
      },
      "KA": {
        "chart": 1.3,
        "tol_pct": 20,
        "note": "boxed [A] — the ONE 820 Ohm carrying both second stages, Normal and Vibrato; the chart prints +1.3 V at each end of the box"
      },
      "PR1": {
        "chart": 170,
        "tol_pct": 20,
        "note": "reverb-recovery plate, 100k from the preamp rail [D]"
      },
      "PD1": {
        "chart": 180,
        "tol_pct": 20,
        "note": "vibrato/reverb mix-driver plate, 100k from the preamp rail [D]"
      },
      "KE": {
        "chart": 1.3,
        "tol_pct": 20,
        "note": "boxed [E] — the ONE 820 Ohm carrying both the mix driver and the reverb recovery; the chart prints +1.3 V at each end of the box"
      },
      "PPIA": {
        "chart": 170,
        "tol_pct": 20,
        "note": "PI plate, 82k (hot) side"
      },
      "PPIB": {
        "chart": 180,
        "tol_pct": 20,
        "note": "PI plate, 100k (cold) side"
      },
      "KPI": {
        "chart": 77,
        "tol_pct": 20,
        "note": "PI joined cathodes, above the 470 Ohm"
      },
      "JPI": {
        "chart": 75.5,
        "tol_pct": 20,
        "note": "PI tail junction (470 Ohm / 22k), grid-leak return"
      }
    }
  },
  "operatingPoint": [
    {
      "node": "S61",
      "chart": 415,
      "sim": 414.017,
      "disputed": false,
      "dev_pct": 0.23686746987951904,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "6V6 (V7) screen after its 470 Ohm-1W stopper, off the +415 plate rail",
      "dispute_note": ""
    },
    {
      "node": "G61",
      "chart": -35,
      "sim": -35,
      "disputed": false,
      "dev_pct": 0,
      "tol_pct": 8,
      "gated": true,
      "within": true,
      "note": "6V6 (V7) grid, fixed bias via 220k from the -35 V supply",
      "dispute_note": ""
    },
    {
      "node": "PRD",
      "chart": 410,
      "sim": 414.258,
      "disputed": false,
      "dev_pct": 1.0385365853658493,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "reverb-driver 12AT7 plate (paralleled sections), off BP1 through the TR4 primary DCR",
      "dispute_note": ""
    },
    {
      "node": "KRD",
      "chart": 8.7,
      "sim": 8.157,
      "disputed": false,
      "dev_pct": 6.241379310344819,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "reverb-driver 12AT7 shared cathode over 2.2k",
      "dispute_note": ""
    },
    {
      "node": "BD",
      "chart": null,
      "sim": 270.186,
      "disputed": false,
      "dev_pct": null,
      "tol_pct": 5,
      "gated": false,
      "within": null,
      "note": "preamp rail, drawing node [D] — the drawing prints no voltage here; derived from the +325 V node through the 10k dropper",
      "dispute_note": ""
    },
    {
      "node": "PN1",
      "chart": 180,
      "sim": 176.251,
      "disputed": false,
      "dev_pct": 2.082777777777775,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "Normal-channel input plate, 100k from the preamp rail [D]",
      "dispute_note": ""
    },
    {
      "node": "KN1",
      "chart": 1.3,
      "sim": 1.409,
      "disputed": false,
      "dev_pct": 8.384615384615383,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "Normal-channel input cathode over 1.5k",
      "dispute_note": ""
    },
    {
      "node": "PN2",
      "chart": 180,
      "sim": 180.117,
      "disputed": false,
      "dev_pct": 0.06499999999999456,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "Normal-channel 2nd-stage plate, 100k from the preamp rail [D]",
      "dispute_note": ""
    },
    {
      "node": "PV1",
      "chart": 170,
      "sim": 176.251,
      "disputed": false,
      "dev_pct": 3.6770588235294146,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "Vibrato-channel input plate, 100k from the preamp rail [D]",
      "dispute_note": ""
    },
    {
      "node": "KV1",
      "chart": 1.3,
      "sim": 1.409,
      "disputed": false,
      "dev_pct": 8.384615384615383,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "Vibrato-channel input cathode over 1.5k",
      "dispute_note": ""
    },
    {
      "node": "PV2",
      "chart": 170,
      "sim": 180.117,
      "disputed": false,
      "dev_pct": 5.95117647058823,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "Vibrato-channel 2nd-stage plate, 100k from the preamp rail [D]",
      "dispute_note": ""
    },
    {
      "node": "KA",
      "chart": 1.3,
      "sim": 1.477,
      "disputed": false,
      "dev_pct": 13.615384615384619,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "boxed [A] — the ONE 820 Ohm carrying both second stages, Normal and Vibrato; the chart prints +1.3 V at each end of the box",
      "dispute_note": ""
    },
    {
      "node": "PR1",
      "chart": 170,
      "sim": 180.117,
      "disputed": false,
      "dev_pct": 5.95117647058823,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "reverb-recovery plate, 100k from the preamp rail [D]",
      "dispute_note": ""
    },
    {
      "node": "PD1",
      "chart": 180,
      "sim": 180.117,
      "disputed": false,
      "dev_pct": 0.06499999999999456,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "vibrato/reverb mix-driver plate, 100k from the preamp rail [D]",
      "dispute_note": ""
    },
    {
      "node": "KE",
      "chart": 1.3,
      "sim": 1.477,
      "disputed": false,
      "dev_pct": 13.615384615384619,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "boxed [E] — the ONE 820 Ohm carrying both the mix driver and the reverb recovery; the chart prints +1.3 V at each end of the box",
      "dispute_note": ""
    },
    {
      "node": "PPIA",
      "chart": 170,
      "sim": 187.812,
      "disputed": false,
      "dev_pct": 10.477647058823536,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "PI plate, 82k (hot) side",
      "dispute_note": ""
    },
    {
      "node": "PPIB",
      "chart": 180,
      "sim": 182.765,
      "disputed": false,
      "dev_pct": 1.5361111111111037,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "PI plate, 100k (cold) side",
      "dispute_note": ""
    },
    {
      "node": "KPI",
      "chart": 77,
      "sim": 69.691,
      "disputed": false,
      "dev_pct": 9.49220779220779,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "PI joined cathodes, above the 470 Ohm",
      "dispute_note": ""
    },
    {
      "node": "JPI",
      "chart": 75.5,
      "sim": 68.236,
      "disputed": false,
      "dev_pct": 9.621192052980126,
      "tol_pct": 20,
      "gated": true,
      "within": true,
      "note": "PI tail junction (470 Ohm / 22k), grid-leak return",
      "dispute_note": ""
    }
  ],
  "checks": [
    {
      "id": "dc",
      "title": "DC operating point",
      "status": "Verified",
      "summary": "18 reference nodes are within tolerance. Maintainer verification is recorded for 2026-07-19; 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.",
        "19 sheet-only parts are explicitly excluded: CB1, CBRV, CDEATH, DBIAS, R1n, R1v, R2n, R2v, R7s, R8s, RBAL, RBIAS, RGN1, RGR1, RGV1, RSLN, RSLV, RTO1, VRBAL. Heaters and the pilot lamp are checked separately."
      ],
      "tone": "checked"
    },
    {
      "id": "heaters",
      "title": "Heater and filament wiring",
      "status": "Partial",
      "summary": "Some circuits are checked; other heater connections remain unestablished.",
      "details": [
        "Supply-leg grouping still needs confirmation at V1, V2, V3, V4, V5, V6.",
        "V1: pins [4, 5] are one leg at 6.3 V and opposite legs at 12.6 V"
      ],
      "tone": "attention"
    },
    {
      "id": "polarity",
      "title": "Capacitor polarity",
      "status": "Partial",
      "summary": "2 capacitor markings cannot be confirmed by the DC model.",
      "details": [
        "CKTO2: CKTO2.b: reaches only ground, through RKTO2",
        "CKTO1: CKTO1.b: reaches only ground, through RKTO1"
      ],
      "tone": "attention"
    }
  ],
  "corrections": [
    {
      "id": "ab763-input-leaks-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "ab763"
      ],
      "title": "AB763 input grid leaks at the first input jack",
      "description": "The schematic now hangs each channel's 1 MΩ input leak from input 1's tip, on the jack side of its 68 kΩ stopper, as the factory drawing shows. It had been drawn on the valve's grid. The board already mounted the leaks at the jacks, and no operating point changes.",
      "commit": "3fa0d9d90353c8f990ed8a295db2b6f126fbbcd2",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/3fa0d9d90353c8f990ed8a295db2b6f126fbbcd2"
    },
    {
      "id": "ab763-stoppers-bias-2026-10-03",
      "date": "2026-10-03",
      "amps": [
        "ab763"
      ],
      "title": "AB763 output grid stoppers and bias filter",
      "description": "Each 6V6 grid now has the 1.5 kΩ stopper both factory pages draw at the valve socket. The bias supply has one filter capacitor, lettered 25 µF at 50 V; a second 50 µF capacitor that the drawing does not show has been removed. No operating point changes.",
      "commit": "0d856bbd32bbd0839e563eb58d4c1c216aa3ec94",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/0d856bbd32bbd0839e563eb58d4c1c216aa3ec94"
    },
    {
      "id": "ab763-tail-2026-09-27",
      "date": "2026-09-27",
      "amps": [
        "ab763"
      ],
      "title": "AB763 phase-inverter feedback return",
      "description": "The model, schematic and board now return the phase-inverter tail to the feedback junction shown by the factory drawing. It had been connected directly to ground. The corrected operating point remains within the published chart tolerances.",
      "commit": "052aec37c520c9df7f6c28cd55fe35aae700229d",
      "url": "https://github.com/TheAnalogMaker/circuit-codex/commit/052aec37c520c9df7f6c28cd55fe35aae700229d"
    }
  ],
  "sourceDirectory": "https://github.com/TheAnalogMaker/circuit-codex/tree/ebddc3fd2cf887dca010bbe60487d7391ea6c052/amps/ab763"
}