5E3 — Tweed Deluxe-style

Verification details

Each check covers a different part of this reference. The circuit badge records the DC comparison and maintainer review.

View checks, findings and exclusions

DC operating point Verified: 7 reference nodes are within tolerance. Maintainer verification is recorded for 2026-07-18; changes since then are awaiting maintainer re-review.
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.
Schematic against DC model Checked: Connectivity of modelled components is checked on every change.
Parts outside the DC model need separate checks and source review.
Board against DC model Checked: Connectivity of modelled components is checked on every change.
This does not establish heater wiring or physical spacing.
Schematic against board No open findings: No disagreement is listed in the published comparison.
A finding identifies a difference or a coverage gap. The factory source must decide which drawing, if either, needs correction.
2 sheet-only parts are explicitly excluded: R3s, R4s. Heaters and the pilot lamp are checked separately.
Heater and filament wiring Checked: The declared heater circuits cover the drawing and pass their separate wiring check.
Capacitor polarity Checked: 6 capacitor markings agree with the model's voltage ordering.
This check uses DC voltage ordering; source review establishes markings the model cannot decide.

Archive revision ebddc3f. Published corrections. These checks do not certify a physical build.

Schematic — redrawn in KiCad · scroll to zoom, drag to pan

Interactive schematic requires JavaScript. Download the redrawn KiCad schematic for 5E3: schematic.kicad_sch.

Machine-checked drawing. This sheet is checked in CI against the netlist the simulation solves: every component the netlist models is proved to have its terminals on the same nodes in this drawing as in that netlist, so the picture and the maths cannot drift apart.

Details

The check compares connectivity, and only as far as the netlist reaches. It does not check component values, and it does not prove the netlist itself a faithful reading of the factory drawing — that rests on the operating-point comparison below and on the cited sources. The netlist is a DC model, so what it leaves out is drawn here but outside this check: the supply front end ahead of the first rail, transformer winding resistance, the volume / tone / mixer control networks and the capacitors inside them, and the heater and AC-side wiring. Separate checks cover drawing-to-board agreement, declared heater circuits and polarity where the model can decide it; see Verification details for their coverage and findings. Every abstraction this circuit relies on is declared as reviewable data in its own sch_map.yaml, and the CI report enumerates each terminal left unchecked.

Board layout — redrawn reference diagram · source noted on the drawing Print sheet ↗

5E3 eyelet board layout — an original diagram redrawn from the published layout drawing, showing the principal parts in the order that drawing places them on the board, drawn in the period layout-sheet style with each value lettered on the part.

Scroll the drawing sideways to read the whole board — the source line and the colour legend run along the bottom of the sheet — or open the full-size diagram in its own tab. Values are lettered on the parts in the period shorthand — .02-400, 250-5, 1MEG: how to read it.

Machine-checked wiring. Every modelled part the operating-point netlist places on this board has been verified in CI, terminal for terminal, to be electrically equivalent to the simulated netlist this circuit is verified against. This diagram documents connectivity and part arrangement — it is not a dimensioned 1:1 build template.

Details

The modelled parts are the tube sockets, the plate, cathode and grid-leak resistors, the power-rail droppers, and the coupling and bypass capacitors whose two leads are both named DC nodes; the check proves the same net structure, with no missing or extra connections. Parts outside that DC model — the volume / tone / mixer control-network internals, the negative-bias front end, and the heater chain, pilot lamp and power-transformer / rectifier AC side — are drawn from the cited sources but are outside this DC equivalence check. Separate checks compare the drawings and examine declared heater circuits and polarity; see Verification details for their coverage and findings.

Board and part positions are drawn at diagram scale, and lead dress, grounding paths, and physical spacing all matter in a high-voltage chassis. If you build from it, verify every connection against the schematic above and the operating-point table below as you go.

Operating point vs. published chart

Chart values read from the published drawing — or, where the drawing carries no voltage chart, from the cited published measurements (never reproduced). The simulated column is this circuit's own netlist solved in ngspice by the run that gates it; every deviation beside it is those two numbers compared, not a separately stated figure. Tolerances are this project's verification targets: tube-pin nodes carry the tolerance the cited source states, or ±20% — the era's printed convention — where it states none, and power rails are held to tighter internal targets. Every gated node lands within target — worst deviation 12.9%.

Node	Chart	Simulated	Deviation	Tolerance	Note
BP2	295 V	319.2 V	8.2%	±15%	screens node (after the 5 kΩ dropper)
BP3	250 V	234.2 V	6.3%	±15%	preamp node (after the 22 kΩ dropper)
PAY1	140 V	122.0 V	12.9%	±20%	12AY7 plate — Robinette: 110 V drop across 100k from 250 V
PAY2	140 V	122.0 V	12.9%	±20%	12AY7 plate (second channel)
P2A	167 V	151.5 V	9.3%	±20%	12AX7 V2A plate — 83 V drop across 100k
PPI	203 V	189.6 V	6.6%	±20%	cathodyne plate — 47 V drop across 56k
KPI	—	45.8 V	—	—	informational — cathodyne cathode (self-biased via 1.5 kΩ/56 kΩ stack)
JPI	—	44.6 V	—	—	informational — grid-leak return junction
KAY	—	1.8 V	—	—	informational — shared 12AY7 cathode
K2A	—	1.2 V	—	—	informational — V2A cathode (1.5 k bias)
K66	19 V	20.5 V	7.7%	±20%	shared 6V6 cathode, 250 Ω 5 W

Tube-pin nodes are checked at the tolerance the cited source states, or at the era's ±20% convention where it states none; power-rail nodes are held to tighter internal verification targets. Simulated figures are the netlist's DC solution, not measurements from a chassis.

The output stage behind these numbers can be drawn: the load line explorer plots this circuit's 6V6GT pair at the DC operating point its netlist carries — 370 V on the plates with a 250 Ω cathode resistor — and marks where the load line crosses.

Parts list

Every designator in this list appears on the schematic above, and every designator on the schematic appears here — the two are checked against each other in both directions, a valve's two halves counting as one bottle (V1A and V1B are both V1). One part the drawing carries as an annotation rather than a numbered symbol is listed here without a designator, and stands outside that check. Each channel has two input jacks, each through its own 68 kΩ into the grid, with the channel's 1 MΩ leak from jack 1's tip to ground, as F-EE draws it on both pages; the jacks themselves and their normalling contacts are not listed. Dropper wattages are not marked on the drawing.

Ref	Part	Value / rating	Role
R1s	Carbon comp resistor	68 kΩ · ½ W	Instrument grid stopper (jack 1)
R1s2	Carbon comp resistor	68 kΩ · ½ W	Instrument grid stopper (jack 2)
R2s	Carbon comp resistor	68 kΩ · ½ W	Mic grid stopper (jack 1)
R2s2	Carbon comp resistor	68 kΩ · ½ W	Mic grid stopper (jack 2)
RG1	Carbon comp resistor	1 MΩ · ½ W	Instrument input leak, jack 1's tip to ground (the V1A grid returns through R1s)
RG2	Carbon comp resistor	1 MΩ · ½ W	Mic input leak, jack 1's tip to ground (the V1B grid returns through R2s)
RL1	Carbon comp resistor	100 kΩ · ½ W	V1A plate load
RL2	Carbon comp resistor	100 kΩ · ½ W	V1B plate load
RK1	Carbon comp resistor	820 Ω · ½ W	Shared 12AY7 cathode bias
C10	Electrolytic capacitor	25 µF · 25 V	Shared 12AY7 cathode bypass
C1	Coupling capacitor	0.1 µF · 400 V	V1A → instrument volume's wiper
C2	Coupling capacitor	0.1 µF · 400 V	V1B → mic volume's wiper
VR1	Audio-taper potentiometer	1 MΩ	Instrument volume: fed on its wiper; one end to ground, the other to the V2A grid line
VR2	Audio-taper potentiometer	1 MΩ	Mic volume: fed on its wiper; one end to ground, the other to the V2A grid line
RL3	Carbon comp resistor	100 kΩ · ½ W	V2A plate load
RK2	Carbon comp resistor	1.5 kΩ · ½ W	V2A cathode bias
C4	Electrolytic capacitor	25 µF · 25 V	V2A cathode bypass
C3	Capacitor	value not legible	V2A plate → cathodyne grid coupler. The schematic draws it with no value; the layout letters it ".02 .1FD. 600 VOLTS", an overwritten revision whose digit cannot be decided (.02 or .1 µF), so no value is given. 600 V on the layout. DC-open, so not in the DC model
C5	Mica capacitor	500 pF	Tone: instrument volume's wiper → tone pot end
VR3	Audio-taper potentiometer	1 MΩ	Tone: track between the 500 pF and the 0.005 µF, wiper on the V2A grid line
C6	Film capacitor	0.005 µF · 600 V	Tone: tone pot's other end → ground
RL4	Carbon comp resistor	56 kΩ · ½ W	Cathodyne plate load
RKA	Carbon comp resistor	1.5 kΩ · ½ W	Cathodyne bias (cathode → junction)
RKB	Carbon comp resistor	56 kΩ · ½ W	Cathodyne cathode load (junction → ground)
RGPI	Carbon comp resistor	1 MΩ · ½ W	Cathodyne grid leak, returned to the junction
C7	Coupling capacitor	0.1 µF · 400 V	Cathodyne plate → V3 grid
C8	Coupling capacitor	0.1 µF · 200 V	Cathodyne cathode → V4 grid
R3s	Carbon comp resistor	1.5 kΩ · ½ W	V3 grid stopper
R4s	Carbon comp resistor	1.5 kΩ · ½ W	V4 grid stopper
RG6A	Carbon comp resistor	220 kΩ · ½ W	V3 grid leak
RG6B	Carbon comp resistor	220 kΩ · ½ W	V4 grid leak
RK66	Wirewound resistor	250 Ω · 5 W	Shared 6V6 cathode bias
C9	Electrolytic capacitor	25 µF · 25 V	Shared 6V6 cathode bypass
RD1	Power resistor	5 kΩ	Rail dropper B+1 → B+2
RD2	Power resistor	22 kΩ	Rail dropper B+2 → B+3
C11	Electrolytic capacitor	16 µF · 450 V	Filter, B+1
C12	Electrolytic capacitor	16 µF · 450 V	Filter, B+2
C13	Electrolytic capacitor	16 µF · 450 V	Filter, B+3
V1	Preamp tube	12AY7	Both input stages (V1A/V1B)
V2	Preamp tube	12AX7	Second stage + cathodyne (V2A/V2B)
V3	Power tube	6V6GT	Push-pull output (upper)
V4	Power tube	6V6GT	Push-pull output (lower)
V5	Rectifier tube	5Y3GT	Full-wave rectifier (V5A/V5B)
T2	Output transformer	8 kΩ : 8 Ω	Push-pull output
—	Power transformer	325-0-325 V · 6.3 V · 5 V	HT + heaters + rectifier filament

Circuit story

The most-built amp circuit in DIY history: two channels into a 12AY7, the famous interactive volume/tone network feeding a 12AX7 second stage, a cathodyne phase inverter, and a cathode-biased 6V6GT push-pull pair with no negative feedback — the recipe for tweed compression and breakup. Produced 1955–1960. Its direct ancestor is the wide-panel 5D3, which shares this tube complement and output stage but inverts phase with a self-balancing paraphase instead.

Circuit walkthrough (short form)

Two channels, each with two input jacks (a 68k stopper per jack, the channel's 1M leak at jack 1's tip) → V1 12AY7 (100k plates, shared 820 Ω bypassed cathode) → 0.1 µF couplers into the wipers of the two 1M volume pots, whose grounded ends and joined grid ends make the interactive pair → V2A 12AX7 (100k plate, 1.5k bypassed cathode) → coupling cap (value not legible on the drawing) → V2B cathodyne phase inverter → 0.1 µF couplers → V3/V4 6V6GT pair (220k grid leaks, 1.5k stoppers, shared 250 Ω 5W bypassed cathode) → 8 kΩ : 8 Ω output transformer.

The volume and tone network

Fender wired the 5E3's volumes backwards from the usual way, and the single tone knob only makes sense once you see it. Each 0.1 µF coupler lands on its volume's wiper. One end of each track goes to ground, and the other ends of both tracks are joined and run to the V2A grid. Turning a channel up moves its wiper toward the grid end. Because the two tracks share that grid line, each volume loads the other channel. The tone pot hangs between the instrument channel's wiper node and ground: 500 pF from that node to one end of the tone track, and 0.005 µF from the other end to ground. Its wiper sits on the shared grid line. It is a treble/cut blend that takes its signal from the instrument channel's coupler and feeds the second stage's input. Both pages of the F-EE drawing show it this way. Until the 2026-10-03 source audit, the corpus drew the conventional wiring instead: couplers on the pot ends, the grid off the wipers, and the tone network between the V2A plate and the phase-inverter grid.

The coupling cap from V2A's plate to the cathodyne grid is drawn on both pages but its value cannot be read. The schematic gives none, and the layout box reads ".02 .1FD. 600 VOLTS", an overwritten revision whose digit could be either .02 or .1 µF. The parts list leaves it as "value not legible" rather than guess. It is DC-open, so the simulation does not need it.

Power: 325-0-325 PT → 5Y3GT → three 16 µF/450 V nodes separated by 5,000 Ω and 22k droppers: B+1 (output plates) → B+2 (screens) → B+3 (preamp).

How the cathodyne biases itself

The 5E3's phase inverter uses a wiring detail that's easy to miss: V2B's cathode runs through 1.5k to a junction, then 56k to ground, and the 1M grid leak returns to that junction rather than to ground, and the coupling cap from V2A's plate AC-couples the grid. The lower output coupler is taken off the cathode itself, at the top of the 1.5k, not off the junction: both the schematic and the layout page draw it there. The stage therefore biases itself: simulation puts the cathode at 45.8 V and the junction at 44.6 V — a clean −1.2 V bias — with the plate (56k from B+3) at 190 V.

The pilot lamp, redrawn

The board used to draw the pilot lamp in series with the heater chain — the green from the transformer into one terminal, the chain leaving from the other — which lights nothing and would blow the lamp. The F-EE layout page draws the lamp with one terminal, the feed arriving and the chain leaving on it, and its return is the holder's shell to the chassis, which the sheet does not draw; the board now draws what the sheet draws and declares the chassis return, and the heater gate proves every pilot lamp sits across the supply's two legs.

Verification

Every component value comes from the published Fender drawing. The F-EE sheet carries no factory voltage chart (only Fender's ±20 % measurement notice), so this circuit is verified against the best published DC measurements instead: all seven reference nodes simulate within 13 % — rails within 8 %, stage plates within 13 %, and the 6V6 cathode within 8 %.

5E3 Tweed Deluxe‑style · 1955–1960 · 15 W

Verification details

Operating point vs. published chart

Parts list

Circuit story

Circuit walkthrough (short form)

The volume and tone network

How the cathodyne biases itself

The pilot lamp, redrawn

Verification

Corrections to this reference

Sources

Verification details

Operating point vs. published chart

Parts list

Circuit story

Circuit walkthrough (short form)

The volume and tone network

How the cathodyne biases itself

The pilot lamp, redrawn

Verification

Corrections to this reference

Sources

Related circuits