The Tympanium regulator rectifier is a compact, solid-state 12-volt charging module for classic British motorcycles with single-phase alternators. One unit replaces the original Lucas selenium rectifier and Zener diode, converting the alternator’s AC output to DC and limiting the voltage that reaches the battery.
Our Tympanium units are manufactured for The Bonneville Shop by Trombetta, the Milwaukee voltage-regulator maker, and supplied to us directly.
It suits a wide range of 12V Triumph, BSA and Norton twins, triples and singles, and it can be wired for positive-ground or negative-ground systems. Check the product details below, then see our regulator and rectifier collection if your bike has a three-phase or high-output stator.
Table of Contents
What Is a Tympanium Regulator Rectifier?
From the factory, most alternator-equipped Triumph, BSA and Norton motorcycles used two separate parts to charge the battery: a Lucas rectifier to turn AC into DC, and one or two Zener diodes to control the voltage. As our solid-state regulator video explains, those original parts are fragile, can deteriorate with age and vibration, and reproduction replacements are often poor quality.
The Tympanium combines both jobs in one sealed module. Installation instructions from Klempf’s British Parts describe it as replacing selenium rectifiers, regulators and Zener diodes on both positive- and negative-ground systems. Tympanium units have been used on British bikes for decades and are still a familiar name among classic owners and restorers.
Watch our video about solid state regulators for more info on your options: VIDEO: About Solid State Regulators
Made by Trombetta
The Tympanium regulator rectifier we sell is manufactured for The Bonneville Shop by Trombetta and comes to us directly from the factory, not through a distributor. Trombetta was founded in Milwaukee, Wisconsin, in 1932 and designs and builds DC contactors, solenoids and voltage regulators for powersports, heavy truck, agricultural and construction equipment (TVH). Since 2021 it has been part of the Engineered Solutions segment of Standard Motor Products. Trombetta’s current range includes single-phase regulator rectifiers for small engines and powersports.
Buying directly from the manufacturer means we know where every unit comes from, and we can answer fitment and wiring questions with confidence.
Shop the unit here: Triumph BSA Norton Tympanium Regulator / Rectifier PN# TBS-4034.
Which Motorcycles Can Use the Tympanium?
The Tympanium TBS-4034 is designed for 12-volt motorcycles with single-phase alternators. Typical applications include:
- Triumph: unit 650 and 750 twins including the T120 Bonneville, TR6 Trophy and Tiger, T140 Bonneville and TR7 Tiger; 500 twins; Trident triples; and singles such as the TR25W. Browse Triumph electrical parts.
- BSA: A50 and A65 twins, including the Thunderbolt and Lightning, plus other single-phase 12V models. Browse BSA electrical parts.
- Norton: single-phase Commando charging systems and other 12V alternator models. Browse Norton electrical parts.
The Tympanium is commonly listed as a 120-watt unit matched to standard single-phase stators such as the Lucas 47205 type (Morrie’s Place Cycle). If your motorcycle has a high-output or three-phase stator, choose one of the alternatives listed below.
Wiring and Installation Basics
Each Tympanium comes with instructions. Before you start, keep these points in mind:
- Two AC inputs, two DC outputs. One published Tympanium wiring sheet shows two yellow leads for the alternator, a red lead and a brown lead. Swapping the red and brown leads sets the system up for positive or negative ground (Klempf’s wiring sheet).
- Three-wire stators. On a three-wire alternator, the same sheet joins the two darker stator leads to one yellow wire and connects the light-colored lead to the other.
- Mount it where air can flow. The instructions say to bolt the unit where it gets airflow or onto a heat sink (Klempf’s British Parts).
- Remove or isolate the old parts. Take off the old Zener diode and rectifier, and tape or remove the wires that are no longer used.
- Fuse the circuit. Fit a correctly rated main fuse, and keep the battery connected while the engine runs.
More instruction sheets are available from British Cycle Supply’s tech help files. For a deeper explanation of how regulator rectifiers work, see the Britspark regulator rectifier guide. Workshop references are in our Triumph manuals, BSA manuals and Norton manuals collections, and the tools you need are under electrical tools.
Tympanium vs. Other Regulator Rectifiers
The Tympanium is a simple, cost-effective single-phase upgrade. Other units suit different charging systems:
| If your bike has… | Consider |
|---|---|
| Standard 12V single-phase stator (10A / 120W) | Tympanium TBS-4034 or Podtronics 120W TBS-4034 T |
| 16A / 200W high-output single-phase stator | Podtronics 200W units, the Podtronics 16A/200W battery eliminator TBS-4030, or the Lucas MOSFET MUR25A |
| Three-phase stator (such as the Lucas RM24) | Podtronics 3-phase TBS-4034AT, the Lucas 3-phase TBS-4034 AW, or the Tri-Spark MOSFET 20A |
| A concours restoration that needs a stock look | Sparx regulator rectifier in a Zener heat sink, TBS-0018 |
| No battery, or a minimal chopper/café wiring setup | Boyer Bransden Power Box or the Podtronics TBS-4030 battery eliminator |
| A 6-volt positive-ground system | 6V positive-ground regulator TBS-4036 |
Like Podtronics and Boyer Power Box units, the Tympanium is a “short” (shunt) type regulator. It controls voltage by shorting surplus alternator output, so the stator, not the regulator, handles most of the heat (Access Norton discussion). MOSFET designs such as the Lucas MUR25A run cooler and can be mounted in more places.
Upgrading the Whole Charging System
If the stator or rotor is tired, replacing only the regulator may not fix poor charging. Browse our charging system collection for stators and rotors, including the Lucas RM24 three-phase stator, the Lucas 16A / 200W single-phase stator and the complete Triumph 650/750 high-output alternator kit. Converting from 6V to 12V? The Sparx 6V stator page explains how it can also be wired into a 12V system.
To refresh the wiring as well, look at our British Wiring harnesses and the full electrical products range.
Ordering and Support
Electrical components cannot be returned, so please confirm your stator type, voltage and ground polarity before ordering. See our shipping and returns policy for details. If you are unsure which regulator suits your bike, contact us or call 720-570-7884 before you buy. We are glad to help you choose the right unit.
Looking for other suppliers? Browse all brands we carry.
Tympanium FAQs
What does a Tympanium regulator rectifier do?
It converts the AC output of your motorcycle’s alternator into DC to charge the battery and limits the charging voltage so the battery and electrical parts are not overcharged. It replaces the separate Lucas rectifier and Zener diode used from the factory.
Who makes the Tympanium regulator rectifier?
The Tympanium units sold by The Bonneville Shop are manufactured for us by Trombetta, a Milwaukee, Wisconsin maker of voltage regulators and DC power products that is now part of Standard Motor Products. We buy them directly from Trombetta.
Which motorcycles does the Tympanium TBS-4034 fit?
It fits 12-volt British motorcycles with single-phase alternators, including Triumph twins, triples and singles (T120 Bonneville, TR6, Tiger, T140, TR7, TR25W), BSA A50 and A65 twins, and Norton Commandos with single-phase charging.
Can I use the Tympanium with a three-phase stator?
No. The TBS-4034 is a single-phase unit. For three-phase stators such as the Lucas RM24, use the Podtronics 3-phase TBS-4034AT, the Lucas 3-phase TBS-4034 AW or the Tri-Spark MOSFET regulator.
Will it work with a 16-amp high-output stator?
The Tympanium is matched to standard 10-amp, 120-watt single-phase stators. For 16A / 200W high-output stators, choose a 200-watt unit such as the Podtronics TBS-4035 or TBS-4030, or the Lucas MOSFET MUR25A.
Does the Tympanium work on positive-ground and negative-ground bikes?
Yes. Positive or negative ground is set by which DC lead you connect to the frame and which goes to the battery. Follow the supplied instructions for your system.
How do I wire a Tympanium regulator rectifier?
Connect the two AC leads (usually yellow) to the alternator, then connect the two DC leads to the battery and frame according to your bike’s ground polarity. On three-wire stators, the darker stator leads are typically joined together. Always follow the instructions supplied with the unit.
Can I run the Tympanium without a battery?
The TBS-4034 is intended for use with a battery in the circuit. For battery-less or minimal setups, a dedicated battery eliminator such as the Podtronics TBS-4030 or a Boyer Bransden Power Box is the better choice. Contact us before building a battery-less system.
Where should I mount the Tympanium?
Mount it where it gets airflow, or bolt it to a metal surface that acts as a heat sink. Avoid enclosed spots where heat builds up.
Can the Tympanium help convert my bike from 6 volts to 12 volts?
It is part of a common 6V-to-12V conversion. You will also need a 12V battery, 12V bulbs and suitable ignition components, and the stator must be wired correctly for 12V operation. Ask us before converting so we can check your system.
How do I know if my regulator rectifier is working?
With a healthy charging system, the battery voltage should rise to roughly 14–14.5 volts when the engine is revved to around 3,000 rpm. Voltage that stays near battery voltage, or climbs well above 15 volts, points to a regulator, stator or wiring fault.
What is the difference between Tympanium, Podtronics and MOSFET regulators?
Tympanium and Podtronics are proven “short” (shunt) type regulators, which load the stator to control voltage. MOSFET regulators such as the Lucas MUR25A and Tri-Spark units run cooler, handle higher outputs and work with both single- and three-phase stators, but cost more.
Can I return a Tympanium regulator if it doesn’t fit?
No. Electrical components cannot be returned, so please confirm your stator type, voltage and ground polarity before ordering. If you are unsure, contact us first and we will help you choose.