FENDER: Tweed Champ Guitar Amplifier Schematics

I know these are everywhere, but humour me - this is mainly for my own reference.

FENDER CHAMP-AMP,  5C1 (WIDE PANEL TWEED)

Note: The Fender Champion 600 and 800 are said to use the same schematic (or at least extremely similar).

Preamp: 6SJ7 pentode, grid-leak biased (no cathode resistor)

• Inputs: two jacks, each 75k in series with 0.02uF (20nF) into the grid

• Grid leak: 5M to ground

• Plate resistor (Ra): 250k

• Screen feed: 2M, bypassed with 0.05uF (50nF)

• Coupling cap to volume: 0.02uF (20nF)

• Volume pot: 1M

Power stage: 6V6 single-ended, cathode biased

• Cathode resistor (Rk): 500 ohms, bypassed with 25uF

• Grid leak resistor = volume pot

Output transformer:  Triad 70189 

Note: I can't find a definitive source of original Champ OT measurements.

• Small single-ended output transformer

• OT Secondary 3.2 ohms 

• OT Primary, usually quoted as ~5k-7k  (some modern replacements offer 5k & 8k primaries). 

Rectifier: 5Y3

Power supply filtering:

• 8uF reservoir → 500 ohms → 8uF (plate/OT node) → 25k → 8uF (screen + preamp node)

Power transformer:  Triad 6500

Typical Voltages:  Actual voltages vary a lot with wall voltage, rectifier condition, and transformer, but the commonly quoted targets for a 5C1 are roughly:

Rectifier DC output (first B+): 340V

B+ after the 500 ohm dropper / main supply node: 320V

6V6 plate: 300V

6V6 screen: 280V (lower because it’s fed through the 25k drop)

6V6 cathode: 16V across the 500 ohm resistor (so ~32mA cathode current as a rough check)

6SJ7 plate: 130V

6SJ7 screen: 21V

6SJ7 grid: -5V

Heaters:  Simple wiring, one side grounded (not twisted pair, no centre tap)

Speaker (stock): 1x6" alnico - commonly Permaflux 6-L (EIA 395), though other 6" period speakers exist due to Fender’s supplier variability and decades of replacements.

FENDER CHAMP 5D1

FENDER CHAMP 5E1

The classic Fender 12AX7 input stage and preamp values are used.  Negative feedback appears.  Choke on the DC power supply.  Changed to a regular component board, controls now on the top of the amp.

Preamp: 12AX7

Inputs: two jacks in the classic Fender input network.  When using input #1, the effective grid-stopper is about 34k because the two 68k resistors end up in parallel

• Each jack feeds the grid through 68k

• Grid leak: 1M to ground

First gain stage (V1A):

• Plate resistor (Ra): 100k

• Cathode resistor (Rk): 1k5, bypassed with 25uF

• Coupling cap to volume: 0.02uF (22nF)

Volume control:

• Volume pot: 1M (between stages)

Second gain / driver stage (V1B):

• Plate resistor (Ra): 100k

• Cathode resistor (Rk): 1k5, not bypassed

• Negative feedback: from OT secondary back to this cathode via a 22k resistor

• Coupling cap to 6V6 grid: 0.02uF (22nF)

Power stage: 6V6 single-ended, cathode biased

• 6V6 grid leak: 220k

• Cathode resistor (Rk): 470 ohms, bypassed with 25uF

• Screen supply: taken from the main B+ node, after the choke

Rectifier: 5Y3GT

Power transformer: Triad 6500

Power supply filtering:

• On 5E1, the choke sits where the 5F1 uses a 10k dropping resistor

• 8uF reservoir → choke → 8uF (main plate/screen/OT node) → 22k → 8uF (preamp node)

Typical voltages (ballpark):

• Main B+ node often lands around ~305V in many examples (varies with wall voltage and rectifier condition)

• 6V6 cathode: ~19V across 470Ω (≈40mA cathode current as a rough check)

• Preamp supply in many references is around ~260V

Speaker (stock):

Commonly a small 6" alnico in early narrow-panel Champs, often a Permaflux (though other 6" period speakers exist due to Fender’s supplier variability and decades of replacements)

FENDER CHAMP 5F1

Almost identical to the previous model, with a 10k resistor replacing the choke.  No bypass on the input triode - less gain.