Machine-checked wiring. Every modelled part the operating-point netlist places on this board — 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 — has been verified in CI, terminal for terminal, to be electrically equivalent to the simulated netlist this circuit is verified against: the same net structure, 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 not machine-checked; the CI report enumerates every one of their terminals so the boundary is explicit rather than silent. This diagram documents connectivity and part arrangement — it is not a dimensioned 1:1 build template. 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). Tolerances are this project's verification targets — tighter on power rails than the ±20% measurement convention Fender printed on its charts. Simulation matches every node within target — worst deviation 14.7%.
| Node | Chart | Tolerance | Note |
|---|---|---|---|
| BP2 | 305 V | ±8% | output B+ after the choke — 6V6 plate (via OT) and screen |
| BP3 | 260 V | ±8% | preamp node after the 22 kΩ dropper |
| P1A | 150 V | ±20% | 12AX7 V1A plate, chart pin value |
| P1B | 150 V | ±20% | 12AX7 V1B plate, chart pin value |
| K1A | 1.5 V | ±20% | 12AX7 V1A cathode, chart pin value (bypassed 25 µF) |
| K1B | 1.5 V | ±20% | 12AX7 V1B cathode (unbypassed; NFB 22k parallels at DC) |
| K2 | 19 V | ±20% | 6V6GT cathode, chart pin value (470 Ω, 25 µF bypass) |
Tube-pin nodes are checked against the chart's own printed ±20% convention; power-rail nodes are held to tighter internal verification targets.
Parts list
Reference designators match the schematic above. Numbering follows the schematic. The AC-line section (power transformer, fuse, line cap) is drawn as annotation only and carries no designator. Values are from the published Champ 5E1 (H-EE) drawing.
| Ref | Part | Value / rating | Role |
|---|---|---|---|
| R1 | Carbon comp resistor | 68 kΩ · ½ W | Input 1 grid stopper |
| R2 | Carbon comp resistor | 68 kΩ · ½ W | Input 2 grid stopper |
| R3 | Carbon comp resistor | 1 MΩ · ½ W | Grid leak |
| R4 | Carbon comp resistor | 1.5 kΩ · ½ W | V1A cathode bias |
| R5 | Carbon comp resistor | 100 kΩ · ½ W | V1A plate load |
| R6 | Carbon comp resistor | 1.5 kΩ · ½ W | V1B cathode bias |
| R7 | Carbon comp resistor | 100 kΩ · ½ W | V1B plate load |
| R8 | Wirewound resistor | 470 Ω · 5 W | 6V6 cathode bias |
| R9 | Carbon comp resistor | 220 kΩ · ½ W | 6V6 grid leak |
| R10 | Power resistor | 22 kΩ · 1 W | Rail dropper B+2→B+3 |
| R11 | Carbon comp resistor | 22 kΩ · ½ W | Negative feedback, speaker→V1B cathode |
| VR1 | Audio-taper potentiometer | 1 MΩ | Volume |
| C1 | Electrolytic capacitor | 25 µF · 25 V | V1A cathode bypass |
| C2 | Coupling capacitor | 0.02 µF · 600 V | V1A → volume |
| C3 | Coupling capacitor | 0.02 µF · 600 V | V1B → 6V6 grid |
| C4 | Electrolytic capacitor | 25 µF · 25 V | 6V6 cathode bypass |
| C5 | Electrolytic capacitor | 8 µF · 450 V | Filter, B+1 (reservoir) |
| C6 | Electrolytic capacitor | 8 µF · 450 V | Filter, B+2 |
| C7 | Electrolytic capacitor | 8 µF · 450 V | Filter, B+3 |
| L1 | Filter choke | ≈350 Ω DCR | B+1→B+2 filter (DCR estimated; not marked on the drawing) |
| V1 | Preamp tube | 12AX7 | Both gain stages (V1A/V1B) |
| V2 | Power tube | 6V6GT | Single-ended output |
| V3 | Rectifier tube | 5Y3GT | Full-wave rectifier (V3A/V3B) |
| T1 | Output transformer | ≈5 kΩ : 8 Ω | Single-ended output (impedance not marked on the drawing; typical SE 6V6 load) |
| — | Power transformer | HT · 6.3 V · 5 V | HT secondary (voltage not marked; +320 V reservoir implies ≈325-0-325) + heater and rectifier windings |
| — | Line capacitor | 0.05 µF · 600 V | Across the AC line at the fuse |
| — | Fuse | 2 A | AC-line fuse |
Circuit story
The mid-1950s tweed Champ: a single 12AX7 giving two gain stages, one 1 MΩ volume control, a cathode-biased 6V6GT single-ended output, and a 5Y3GT rectifier — no tone control and no phase inverter, about five watts of the shortest signal path Fender ever shipped. Produced circa 1955–1957, it is the direct ancestor of the more familiar 5F1: same tube complement and nearly the same preamp, but with a choke-filtered power supply the 5F1 later dropped.
Circuit walkthrough (short form)
Two input jacks (each through its own 68 kΩ stopper, 1 MΩ grid leak) → V1A (12AX7, 100 kΩ plate load, 1.5 kΩ cathode bypassed by 25 µF) → 0.02 µF coupling → 1 MΩ volume pot → V1B (12AX7, 100 kΩ plate load, 1.5 kΩ cathode, left unbypassed so the feedback can work into it) → 0.02 µF coupling → V2 6V6GT (cathode-biased, 470 Ω 5 W with 25 µF bypass, 220 kΩ grid leak) → single-ended output transformer (≈5 kΩ : 8 Ω, typical for a single-ended 6V6; the drawing doesn't mark it) → speaker. Negative feedback: 22 kΩ from the speaker jack into V1B's cathode — at DC this parallels the 1.5 kΩ cathode resistor through the secondary's near-zero DCR.
Power: a center-tapped HT winding feeds the 5Y3GT full-wave rectifier into a choke-filtered supply. The first 8 µF reservoir sits at +320 V; a filter choke drops it to +305 V, which supplies the 6V6 plate (through the output-transformer primary) and its screen; a 22 kΩ resistor then drops the rail to +260 V for the two 12 AX7 plates. Three 8 µF / 450 V cans do the filtering.
The choke, and what changed on the way to the 5F1
The 5E1's supply is the clearest fingerprint separating it from its descendant. Here a choke does the first bit of B+ filtering — reservoir +320 V down to +305 V — and the output tube runs its plate and screen off that single post-choke node. The 5F1 that followed replaced the choke with a plain 10 kΩ resistor, split the plate and screen onto separate rails, and shifted the reservoir up to +340 V. Same amp, quieter-on-paper filtering, one fewer iron part to buy.
Because the choke's DC resistance isn't printed anywhere on the drawing, the model estimates it from the chart itself: a +320 → +305 V drop carrying the roughly 43 mA the printed pin voltages imply works out to about 350 Ω, and the simulation settles on the same 42 mA self-consistently.
Verification
The drawing prints a full voltage chart (Fender's usual "read to ground with an electronic voltmeter, ±20%"), and the simulation matches every node on it: the 6V6 cathode within 0.1 % (+19.0 V vs +19 V), the output rail within 0.1 % (+305 V), and the preamp rail within 2.4 %. The rails are held to a tighter ±8 % internal verification target (the choke's DC resistance is estimated rather than printed, so the archive holds itself to a stricter bar there), while the two 12AX7 plates and cathodes are checked against Fender's printed ±20 % convention. The preamp stages simulate a little lean — plates near +178 V against the chart's +150 V — because the tube models are datasheet-typical while Fender measured production tubes of the day; the same gap shows up on every tweed circuit here. Planned refinements: the output transformer's primary resistance in the DC deck, and full curve-traced tube models.