A tube amplifier is a high-voltage device. Its plate supply runs at 300 to 450 volts — higher in some designs, and higher still cold and unloaded — and its filter capacitors hold that charge for a long time after the amp is switched off and unplugged. This is the standard safety practice every amp manual and repair text sets out — read it before a chassis is ever opened.
The danger is not only the wall socket. It is the energy the amplifier deliberately stores, and keeps storing after the power is gone.
B+ is a lethal voltage. A guitar amp rectifies the power transformer's high-voltage winding up to its plate supply — its B+ — and runs the output tubes from it. In the circuits documented here that rail sits roughly between 300 V and 450 V in normal operation — and some run higher: a 360-0-360 transformer (the JTM45's) can push its reservoir near 500 V idling unloaded, and any supply reads highest when the amp is cold and drawing no current. Mains-frequency current at those potentials, across the body, is far more than enough to stop a heart; it is the current that kills, and a few tens of milliamps is enough.
Filter capacitors store the charge — and hold it. To smooth the rectified supply into steady DC, the amp charges a bank of electrolytic filter capacitors to the full B+. Switch off and the tubes stop drawing, but the capacitors stay charged: a 16 µF capacitor at 450 V holds more than a joule, and with no load to drain it, it can sit at a lethal voltage for many minutes — sometimes hours. A capacitor is, by design, a device for holding a charge, and it does its job long after the amp is dark.
A pilot lamp proves nothing. The lamp goes out and the tubes stop glowing while the reservoir cap is still at hundreds of volts. Some amps fit a bleeder resistor across the first filter cap to drain it slowly, but many do not, and a bleeder can be the wrong value, disconnected, or failed open. Nothing you can see from outside tells you a capacitor is safe. Only a meter, on that capacitor, does.
This is the routine amp technicians run every time a chassis is opened. The idea is simple: bleed each capacitor's charge away through a resistor, then prove with a meter that it is gone — before any part of you enters the chassis. Hover, tap, or focus a step to trace it on the diagram.
Hover, tap, or focus a step to trace it on the diagram.
The procedure is the one given in every reputable amp-repair text and service manual. Clear public write-ups include Rob Robinette's Tube Amp Safety and Merlin Blencowe's The Valve Wizard power-supply notes; the technical library at Aiken Amplification covers the same ground.
Discharging the caps clears the stored charge. These four rules cover the rest — the habits that keep a live-chassis mistake from becoming a fatal one.
Keep one hand in a pocket or behind your back when a circuit may be live, so a shock cannot cross your chest and stop your heart. One hand in, one hand out.
Have someone within earshot who knows where the mains disconnect is and how to break you free of a live circuit without becoming a second casualty.
A bleeder resistor may be absent, wrong, or failed. Treat every filter capacitor as holding full B+ until your own meter, on that cap, proves otherwise.
A meter you trust — rated CAT II 600 V or better, with sound probes — is the only thing that tells you a node is dead. Prove the reading before you reach in.
On the meter: a digital multimeter used near B+ should be rated for the job — CAT II at 600 V or better, with intact leads and probes — and the range set above the expected voltage before the probes touch anything. A meter you have not proven on a known voltage is not evidence a node is dead. The oxblood pins on the tube pinout diagrams mark exactly the points that sit at B+ in service.
These are the high-voltage filter capacitors listed in the corpus, generated straight from each amp's parts list — 149 caps across 39 circuits. Every one of them charges to its node's B+ in service and holds it after power-off. This is the bank the procedure above clears, node by node.
| Ref | Capacitor | Node | In circuit |
|---|---|---|---|
| C5 | 8 µF · 450 V | Filter, B+1 (reservoir) | 5C1 Wide-panel Champ-style |
| C6 | 8 µF · 450 V | Filter, B+2 | 5C1 Wide-panel Champ-style |
| C7 | 8 µF · 450 V | Filter, B+3 | 5C1 Wide-panel Champ-style |
| C11 | 16 µF · 450 V | Filter, B+1 | 5D3 Wide-panel Tweed Deluxe-style |
| C12 | 16 µF · 450 V | Filter, B+2 | 5D3 Wide-panel Tweed Deluxe-style |
| C13 | 16 µF · 450 V | Filter, B+3 | 5D3 Wide-panel Tweed Deluxe-style |
| C5 | 8 µF · 450 V | Filter, B+1 (reservoir) | 5E1 Tweed Champ-style |
| C6 | 8 µF · 450 V | Filter, B+2 | 5E1 Tweed Champ-style |
| C7 | 8 µF · 450 V | Filter, B+3 | 5E1 Tweed Champ-style |
| C11 | 16 µF · 450 V | Filter, B+1 | 5E3 Tweed Deluxe-style |
| C12 | 16 µF · 450 V | Filter, B+2 | 5E3 Tweed Deluxe-style |
| C13 | 16 µF · 450 V | Filter, B+3 | 5E3 Tweed Deluxe-style |
| C11 | 16 µF · 450 V | Filter, B+1 (reservoir) | 5E4-A Tweed Super-style |
| C12 | 16 µF · 450 V | Filter, B+2 | 5E4-A Tweed Super-style |
| C13 | 16 µF · 450 V | Filter, B+3 | 5E4-A Tweed Super-style |
| C14 | 8 µF · 450 V | Filter, B+4 | 5E4-A Tweed Super-style |
| C10 | 16 µF · 450 V | Filter, BP2 (screens) | 5E5-A Tweed Pro-style |
| C11 | 16 µF · 450 V | Filter, BP3 (driver/PI) | 5E5-A Tweed Pro-style |
| C12 | 8 µF · 450 V | Filter, BP4 (preamp) | 5E5-A Tweed Pro-style |
| C10 | 16 µF · 450 V | Filter, B+1 (second of three cans) | 5E6-A Tweed Bassman-style |
| C11 | 16 µF · 450 V | Filter, B+1 (third of three cans) | 5E6-A Tweed Bassman-style |
| C12 | 16 µF · 450 V | Filter, B+2 | 5E6-A Tweed Bassman-style |
| C13 | 8 µF · 450 V | Filter, B+3 | 5E6-A Tweed Bassman-style |
| C9 | 16 µF · 450 V | Filter, B+1 (first of three cans at the same node — plates/screens/OT centre-tap area) | 5E6-A Tweed Bassman-style |
| C5 | 16 µF · 450 V | Filter, B+1 | 5F1 Tweed Champ-style |
| C7 | 8 µF · 450 V | Filter, B+2 | 5F1 Tweed Champ-style |
| C8 | 8 µF · 450 V | Filter, B+3 | 5F1 Tweed Champ-style |
| C10 | 16 µF · 450 V | Filter, B+3 | 5F10 Tweed Harvard-style |
| C8 | 16 µF · 450 V | Filter, B+1 | 5F10 Tweed Harvard-style |
| C9 | 16 µF · 450 V | Filter, B+2 | 5F10 Tweed Harvard-style |
| C10 | 8 µF · 450 V | Filter, B+3 | 5F2-A Tweed Princeton-style |
| C7 | 16 µF · 450 V | Filter, B+1 | 5F2-A Tweed Princeton-style |
| C8 | 16 µF · 450 V | Filter, B+1 (paralleled) | 5F2-A Tweed Princeton-style |
| C9 | 8 µF · 450 V | Filter, B+2 | 5F2-A Tweed Princeton-style |
| C11 | 16 µF · 450 V | Filter, B+1 (reservoir) | 5F4 Tweed Super-style |
| C12 | 16 µF · 450 V | Filter, B+2 | 5F4 Tweed Super-style |
| C13 | 16 µF · 450 V | Filter, B+3 | 5F4 Tweed Super-style |
| C14 | 8 µF · 450 V | Filter, B+4 | 5F4 Tweed Super-style |
| C14 | 20 µF · 600 V | Filter, B+1 | 5F6 Tweed Bassman-style |
| C15 | 20 µF · 600 V | Filter, B+1 (second, in parallel with C14) | 5F6 Tweed Bassman-style |
| C16 | 20 µF · 600 V | Filter, B+2 | 5F6 Tweed Bassman-style |
| C17 | 20 µF · 600 V | Filter, B+3 | 5F6 Tweed Bassman-style |
| C18 | 8 µF · 450 V | Filter, B+4 | 5F6 Tweed Bassman-style |
| C11 | 20 µF · 600 V | Filter, B+1 | 5F6-A Tweed Bassman-style |
| C12 | 20 µF · 600 V | Filter, B+2 | 5F6-A Tweed Bassman-style |
| C13 | 20 µF · 600 V | Filter, B+3 | 5F6-A Tweed Bassman-style |
| C14 | 8 µF · 450 V | Filter, B+4 | 5F6-A Tweed Bassman-style |
| CF1 | 20 µF · 450 V | Reservoir can — the 6973 plate node and the output-transformer centre tap | 6161 Valco 6161-style |
| C11 | 30 µF · 450 V | Reservoir filter, +315 V | 6G2 Brown Princeton-style |
| C12 | 30 µF · 450 V | Filter, +312 V screen node | 6G2 Brown Princeton-style |
| C13 | 30 µF · 450 V | Filter, +280 V preamp/PI node | 6G2 Brown Princeton-style |
| C21 | 16 µF · 450 V | Reservoir filter, +375 V | 6G3 Brown Deluxe-style |
| C22 | 16 µF · 450 V | Filter, +365 V screen node | 6G3 Brown Deluxe-style |
| C23 | 16 µF · 450 V | Filter, +325 V phase-inverter node | 6G3 Brown Deluxe-style |
| C24 | 8 µF · 450 V | Filter, +270 V preamp node | 6G3 Brown Deluxe-style |
| C10 | 20 µF · 600 V | HT filter, lettered 20-600 on the drawing and repeated at several rail nodes (the per-node count is not resolved at this scan's resolution) | 6G4 Brown Super-style |
| CF3 | 20 µF · 600 V | B+ reservoir, ahead of the choke (per the drawing's repeated '20-600P' marking) | 6G5 Brown Pro-style |
| CF4 | 20 µF · 600 V | Filter, BP1 (6L6GC plates, post-choke) | 6G5 Brown Pro-style |
| CF5 | 20 µF · 600 V | Filter, BP2 (screens) | 6G5 Brown Pro-style |
| CF6 | 20 µF · 600 V | Filter, along the 56k/10k dropper chain toward the PI/driver/preamp supplies | 6G5 Brown Pro-style |
| CF7 | 20 µF · 600 V | Filter, along the 56k/10k dropper chain toward the PI/driver/preamp supplies | 6G5 Brown Pro-style |
| C10 | 20 µF · 600 V | Filter, first B+ node | 6G6-B Blonde Bassman-style |
| C11 | 20 µF · 600 V | Filter, B+ after choke | 6G6-B Blonde Bassman-style |
| C12 | 20 µF · 600 V (×2, dual) | Filter, driver/preamp B+ taps | 6G6-B Blonde Bassman-style |
| C14 | 20 µF · 600 V | Filter, Bass-row +230 V lane | 6G6-B Blonde Bassman-style |
| CF1 | 20 µF · 450 V | Reservoir filter (+420 V, OT centre tap) | AA1164 Blackface Princeton Reverb-style |
| CF2 | 20 µF · 450 V | Filter, screen rail (+400 V) | AA1164 Blackface Princeton Reverb-style |
| CF3 | 20 µF · 450 V | Filter, +320 V node | AA1164 Blackface Princeton Reverb-style |
| CF4 | 20 µF · 450 V | Filter, preamp / phase-inverter rail (+240 V) | AA1164 Blackface Princeton Reverb-style |
| C10 | 20 µF · 450 V | Filter, B+3 (preamp) | AA764 Blackface Champ-style |
| C8 | 20 µF · 450 V | Filter, B+1 (reservoir) | AA764 Blackface Champ-style |
| C9 | 20 µF · 450 V | Filter, B+2 (screen) | AA764 Blackface Champ-style |
| C10 | 20 µF · 450 V | Filter, B+3 (preamp) | AA764 (Vibro Champ-style) Blackface Vibro Champ-style |
| C8 | 20 µF · 450 V | Filter, B+1 (reservoir) | AA764 (Vibro Champ-style) Blackface Vibro Champ-style |
| C9 | 20 µF · 450 V | Filter, B+2 (screen) | AA764 (Vibro Champ-style) Blackface Vibro Champ-style |
| C10 | 70 µF · 350 V | Reservoir, upper half of the series pair (+422 V node) | AA864 (Bassman-style) Blackface Bassman-style |
| C11 | 70 µF · 350 V | Reservoir, lower half of the series pair | AA864 (Bassman-style) Blackface Bassman-style |
| C12 | 20 µF · 525 V | Filter, screen rail (+420 V, past the choke) | AA864 (Bassman-style) Blackface Bassman-style |
| C13 | 20 µF · 525 V | Filter, phase-inverter rail (+410 V) | AA864 (Bassman-style) Blackface Bassman-style |
| C14 | 20 µF · 525 V | Filter, preamp rail (+380 V on the layout sheet — see voltages.yaml) | AA864 (Bassman-style) Blackface Bassman-style |
| CA | 20 µF · 450 V | Reservoir filter, +420 V node | AA964 Blackface Princeton-style |
| CB | 20 µF · 450 V | Filter, screen rail (+415 V) | AA964 Blackface Princeton-style |
| CC | 20 µF · 450 V | Filter, node between the two 18 kΩ droppers | AA964 Blackface Princeton-style |
| CD | 20 µF · 450 V | Filter, preamp and inverter rail (+290 V) | AA964 Blackface Princeton-style |
| C10 | 70 µF · 350 V | Reservoir filter, upper half of the series pair | AB165 Blackface Bassman-style |
| C11 | 70 µF · 350 V | Reservoir filter, lower half of the series pair | AB165 Blackface Bassman-style |
| C12 | 20 µF · 525 V | Filter, screen node (+425, after the choke) | AB165 Blackface Bassman-style |
| C13 | 20 µF · 525 V | Filter, phase-inverter node (+415) | AB165 Blackface Bassman-style |
| C14 | 20 µF · 525 V | Filter, second-stage node (+390) | AB165 Blackface Bassman-style |
| C15 | 8 µF · 450 V | Filter, input-stage node (+320) | AB165 Blackface Bassman-style |
| C10 | 16 µF · 450 V (×2) | Reservoir filter (post-standby) | AB763 Blackface Deluxe Reverb-style |
| C11 | 16 µF · 450 V | Filter, node B (screens/+415) | AB763 Blackface Deluxe Reverb-style |
| C12 | 16 µF · 450 V | Filter, node C (+325 PI/preamp) | AB763 Blackface Deluxe Reverb-style |
| C13 | 16 µF · 450 V | Filter, node D (input-stage rail) | AB763 Blackface Deluxe Reverb-style |
| C10 | 70 µF · 350 V (×2) | Reservoir filter (post-standby) | AB763 (Super Reverb-style) Blackface Super Reverb-style |
| C11 | 20 µF · 525 V | Filter, node B (screens/BP1) | AB763 (Super Reverb-style) Blackface Super Reverb-style |
| C12 | 20 µF · 525 V | Filter, node C (PI/reverb-driver rail) | AB763 (Super Reverb-style) Blackface Super Reverb-style |
| C10 | 70 µF · 350 V | Reservoir filter, upper half of the series pair | AB763 (Twin Reverb-style) Blackface Twin Reverb-style |
| C11 | 70 µF · 350 V | Reservoir filter, lower half of the series pair | AB763 (Twin Reverb-style) Blackface Twin Reverb-style |
| C12 | 20 µF · 525 V | Filter, node [B] (+458, screens) | AB763 (Twin Reverb-style) Blackface Twin Reverb-style |
| C13 | 20 µF · 525 V | Filter, node [C] (+450, PI plates) | AB763 (Twin Reverb-style) Blackface Twin Reverb-style |
| C14 | 20 µF · 525 V | Filter, node [D] (+410, preamp plates) | AB763 (Twin Reverb-style) Blackface Twin Reverb-style |
| CR1 | 16 µF · 450 V | Reservoir filter, EZ81 cathode side | AC15 Vox AC15-style |
| CR2 | 16 µF · 450 V | Smoothing filter after the choke | AC15 Vox AC15-style |
| C39 | 16 µF · 450 V | Reservoir filter, GZ34 cathode side | AC30 Vox AC30/6-style |
| C40 | 16 µF · 450 V | Smoothing filter after the choke | AC30 Vox AC30/6-style |
| C16A | 40 µF · 500 V | Screen-node filter — one section of the three-section can the sheet letters C16 | B15N Ampeg B-15N Portaflex-style |
| C16B | 40 µF · 500 V | Preamp-rail filter — the second section of the C16 can | B15N Ampeg B-15N Portaflex-style |
| C16C | 40 µF · 500 V | Driver-rail filter — the third section of the C16 can | B15N Ampeg B-15N Portaflex-style |
| C17 | 30 µF · 600 V | Reservoir — the 5AR4 cathode node, which is also the OT-214 primary centre tap and the 6L6GC anode node | B15N Ampeg B-15N Portaflex-style |
| C17 | 220 µF · 350 V | Reservoir, upper half of the series pair | DR103 Hiwatt Custom 100-style |
| C18 | 220 µF · 350 V | Reservoir, lower half of the series pair | DR103 Hiwatt Custom 100-style |
| C19 | 50 µF · 450 V (×2) | HT2/HT3 filter can, a series pair in one housing | DR103 Hiwatt Custom 100-style |
| C20 | 220 µF · 350 V | HT3 filter | DR103 Hiwatt Custom 100-style |
| C21 | 32 µF · 450 V | Second-stage rail filter | DR103 Hiwatt Custom 100-style |
| C22 | 16 µF · 350 V | Input and driver rail filter | DR103 Hiwatt Custom 100-style |
| CF1 | 20 µF | Reservoir can, ahead of the choke — the 5Y3GT cathode node the chart reads +315 V | GA40 Gibson GA-40 Les Paul-style |
| C13 | 32 µF | HT reservoir, series pair 1 (upper) | JTM100 British 100-watt lead-style |
| C14 | 32 µF | HT reservoir, series pair 1 (lower) | JTM100 British 100-watt lead-style |
| C15 | 32 µF | HT reservoir, series pair 2 (upper) | JTM100 British 100-watt lead-style |
| C16 | 32 µF | HT reservoir, series pair 2 (lower) | JTM100 British 100-watt lead-style |
| C17 | 32 µF | HT reservoir, series pair 3 (upper) | JTM100 British 100-watt lead-style |
| C18 | 32 µF | HT reservoir, series pair 3 (lower) | JTM100 British 100-watt lead-style |
| C19 | 32 µF | Phase-inverter rail filter | JTM100 British 100-watt lead-style |
| C20 | 16 µF | Preamp rail filter | JTM100 British 100-watt lead-style |
| C11 | 32 µF · 500 V | Reservoir filter, B+1 | JTM45 British lead-style |
| C12 | 16 µF · 500 V | Filter, B+2 | JTM45 British lead-style |
| C13 | 16 µF · 500 V | Filter, B+3 | JTM45 British lead-style |
| C14 | 16 µF · 450 V | Filter, B+4 | JTM45 British lead-style |
| C19 | 100 µF · 350 V | Reservoir filter, upper half of a series pair | M1959 Super Lead 100-style |
| C20 | 100 µF · 350 V | Reservoir filter, lower half of a series pair | M1959 Super Lead 100-style |
| C21 | 100 µF · 350 V | Second reservoir bank, upper half of a series pair | M1959 Super Lead 100-style |
| C22 | 100 µF · 350 V | Second reservoir bank, lower half of a series pair | M1959 Super Lead 100-style |
| C23 | 50 µF · 350 V | Phase-inverter-supply filter | M1959 Super Lead 100-style |
| C24 | 50 µF · 350 V | Phase-inverter-supply filter | M1959 Super Lead 100-style |
| C25 | 50 µF · 350 V | Second-stage-supply filter | M1959 Super Lead 100-style |
| C26 | 50 µF · 350 V | Second-stage-supply filter | M1959 Super Lead 100-style |
| C27 | 50 µF · 350 V | Input-stage-supply filter | M1959 Super Lead 100-style |
| C28 | 50 µF · 350 V | Input-stage-supply filter | M1959 Super Lead 100-style |
| C17 | 50 µF · 500 V | Reservoir filter (B+1) | M1987 Plexi lead 50-style |
| C18 | 80 µF · 500 V | Reservoir filter (B+1) | M1987 Plexi lead 50-style |
| C19 | 50 µF · 500 V | Screen-node filter | M1987 Plexi lead 50-style |
| C20 | 50 µF · 500 V | Phase-inverter-supply filter | M1987 Plexi lead 50-style |
| C21 | 50 µF · 350 V | Second-stage-supply filter | M1987 Plexi lead 50-style |
| C22 | 50 µF · 350 V | Input-stage-supply filter | M1987 Plexi lead 50-style |
| C21 | 50 µF + 50 µF | Preamp-rail and input-stage-rail filter, one section each side of R8 | M2204 Master Volume lead 50-style |
| C22 | 50 µF + 50 µF | Screen-node filter after the choke — both sections of the can land on that node (unlike C21, whose sections straddle R8) | M2204 Master Volume lead 50-style |
| C23 | 50 µF + 50 µF | HT reservoir | M2204 Master Volume lead 50-style |
| C25 | 20 µF + 10 µF + 5 µF · 450 V | The whole triple-section filter can, one part in the factory list ('5-10-20 mfd., 450 v.') and one can on the chassis. The schematic letters its sections C25A, C25B and C25C along the two-dropper chain: C25A on the 340 V screen node, C25B between R58 and R59, C25C at the R59 end | S1484 Silvertone Twin Twelve-style |
Values are read from the published parts lists; cathode-bypass and bias-supply electrolytics, which sit at far lower voltages, are left out so the table shows only the caps that hold a dangerous charge.
One era-specific part deserves its own warning: the small capacitor wired from the AC line to the chassis on amps built for two-wire, ungrounded mains. Technicians call it the death cap, and the standard advice is unambiguous — remove it.
A shorted or leaky cap, or a ground switch left on the hot leg, puts the full line voltage on the chassis. Anyone touching the chassis and ground completes the circuit.
The chassis is tied straight to the mains safety earth. Hum is handled by the ground, not a cap. No death cap, no ground switch.
What it is. On amps built for two-wire mains — the era before a third, earth conductor was standard — there was no safety ground. To quiet hum, the designer wired a small capacitor, typically 0.05 µF at 600 V, from one leg of the AC line to the chassis, often through a two-position ground or polarity switch that chose which line conductor the cap connected to. The switch let the player flip the plug's effective orientation to find the quieter setting.
Why it was there. With no earth ground, the cap gave the chassis a high-impedance AC path to the grounded (neutral) side of the line, shunting hum and RF away. On the two-prong wiring of the day it was a reasonable, common trick, and it appears across tweed-era amplifiers.
Why it is unsafe on modern mains. A two-wire plug can go into the socket either way, so there is no guarantee which prong is neutral. If the plug or the switch connects the cap — and through it the chassis — to the hot leg, the chassis is coupled to the live line. Worse, these capacitors age and fail shorted: a failed death cap ties the chassis directly to a line conductor at full mains potential. The chassis, the guitar's strings through the amp ground, and a connected microphone all become live, and a person touching any of them and a grounded surface completes the circuit. This arrangement has caused electrocutions, which is how it earned its name.
The fix everyone agrees on. Remove the death cap and the ground switch entirely, and replace the two-wire cord with a modern three-wire grounded cord: line and neutral to the fuse, switch, and power transformer as before, and the third (green) earth conductor bonded directly to the chassis at a solid ground point. The chassis is then held at earth potential by the mains ground, not floated through a capacitor, and any fault trips the breaker instead of energising the chassis. Adding a proper earth is not enough on its own — the cap and switch come out. This is the standard, universally recommended conversion for any vintage amp returned to service.
The era cap appears on the AC-line network of these circuits in the archive — drawn as period annotation, never as a part to keep:
| Capacitor | As drawn | Circuit |
|---|---|---|
| 0.05 µF · 600 V | Across the AC line at the fuse | 5C1 Wide-panel Champ-style |
| 0.05 µF · 600 V | Across the AC line at the fuse | 5E1 Tweed Champ-style |
| 0.05 µF · 600 V (×2) | AC-line filter caps (annotation only) | 5E4-A Tweed Super-style |
| 0.05 µF · 600 V (×2) | AC-line bypass, ground switch / AC switch (annotation only) | 5E6-A Tweed Bassman-style |
| 0.05 µF · 600 V | AC-line filter caps (×2, annotation only) | 5F10 Tweed Harvard-style |
| 0.05 µF · 600 V | Across the AC line | 5F2-A Tweed Princeton-style |
| 0.05 µF · 600 V (×2) | AC-line filter caps (annotation only) | 5F4 Tweed Super-style |
| 0.05 µF | Mains line-to-chassis capacitor | M1959 Super Lead 100-style |
| 0.05 µF · 600 V | Line-to-chassis capacitor across the ground switch — the era's 'death cap'; period practice, never fitted in a modern build | S1484 Silvertone Twin Twelve-style |
On the death cap and the three-wire conversion, see Rob Robinette's Tube Amp Safety. The period arrangement is visible on the factory drawings this archive cites, among them the Champ 5E1 and other tweed schematics archived at EL34World.
This page collects the safety practice common to the amp-repair literature and the original service manuals. The references below are linked, never rehosted; the manufacturer manuals of the era sit on the reference shelf.
This primer describes standard practice; it is not a substitute for hands-on training. High-voltage work carries real risk of injury and death, and the responsibility for working safely rests with the person holding the probes. If any part of the routine above is unfamiliar, do not open a powered or recently-powered amplifier — learn the practice first, ideally alongside someone who already works on these circuits.