TOSOKU Manual Electro Sync Pulse Generator MPG RE45BA1R5

Tosoku RE45BA1R5 | OEM Replacement Manual Pulse Generator — 5V DC, 100 PPR, Voltage Output, 80mm Dial, Japan

When You Need This Part

Most maintenance engineers looking for this part already know the drill: the handwheel on a machining centre or turning centre has started misbehaving — the axis drifts one way when you turn the dial the other, or certain turns produce no movement at all, or the motion is jumpy even at the finest magnification setting.

The machine has been running for years, the original Tosoku encoder has accumulated hundreds of thousands of dial rotations, and it is finally showing its age.

The RE45BA1R5 is the part you need.

It is the direct replacement for the RE45BA1R5C (the current suffix-updated production version carries a C at the end, but the core specification and fitment are identical to the original RE45BA1R5).

The 5V voltage output, 100 PPR, and 80mm dial combination represents the most widely deployed RE45B variant in CNC machine tool panels across Asia, Europe, and North America — it is the configuration that Fanuc, Mitsubishi, Mazak, Haas, and dozens of other machine tool builders have specified in their operator panels for decades.

Sourcing a replacement should be straightforward if you go directly to Tosoku's authorised distribution network.

Beware of low-cost copies — the RE45B is one of the most copied MPG encoders on the market, and the copies range from nearly functional to completely useless after a few weeks.

The Tosoku original has proven longevity in production environments precisely because the optical sensing mechanism, the detent mechanism, and the mechanical construction are manufactured to tolerances that generic copies do not match.

Identifying the RE45BA1R5 on Your Machine

The part number is typically printed on a label on the rear face of the encoder body, visible once the operator panel is opened. Look for "RE45BA1R5" or "RE45BA1R5C" (the C suffix is a minor revision update, fully equivalent to the base part).

The three mounting nuts visible from the front of the operator panel identify it as a Type A (3-nut mount), and the black dial with Tosoku's logo on the black 15mm knob confirms the B-type knob configuration.

If the label on your encoder is damaged or missing, the physical identification is:

• 80mm diameter black plastic dial with indexed markings
• Three panel mounting nuts at roughly 120° spacing visible from the front
• Rear connector exit (the wiring form depends on whether the machine uses Tosoku's standard wiring or a custom harness from the machine builder)
• Made in Japan — the housing back will typically show Japan country of origin

The related RE45BA1D5 looks identical from the front but draws 150mA at 5V and uses a differential line driver output — it is not electrically interchangeable with the R5 voltage output variant without rewiring the CNC's MPG input. Confirm the original part number before ordering.

The RE45BA1R5 vs RE45BA1R5C — Are They the Same?

Yes. The C suffix on the RE45BA1R5C represents a minor revision within the same product generation — Tosoku periodically updates the suffix letter to track production changes that are fully backward compatible.

The mounting, electrical connections, supply voltage, resolution, output format, and mechanical dimensions are unchanged between RE45BA1R5 and RE45BA1R5C. The two part numbers are interchangeable for replacement purposes.

Some authorised distributors list only the C variant (as the current shipping version); do not be concerned that you are not getting the exact original designation.

Recognising a Failing MPG Before It Stops Completely

MPG encoders rarely fail all at once. More commonly, they degrade gradually, and the symptoms are easy to misdiagnose if you are not looking for them specifically.

Missing pulses at certain angles. The optical disc develops a smear or fine scratch across one or more of its tracks, causing the photodetector to miss pulses in that segment of the rotation.

At the ×1 magnification setting, this shows up as occasional missed steps — the axis moves 0.001mm per detent most of the time but occasionally does not respond. At ×100, the same fault may go unnoticed because the larger commanded movement per pulse masks the skip.

Reversed direction on partial turns. A contaminated disc or a worn photodetector circuit causes the A/B phase relationship to be misread momentarily, causing the CNC to count one step backward before resuming normal forward counting.

This looks like a slight oscillation or backlash-like error during slow handwheel movement.

No output on first turn after startup. The optical emitter (LED) inside the encoder has aged to the point where it takes a moment to reach stable output intensity after power-up. In the first few seconds, the signal is too weak for the photodetector to read reliably.

This typically progresses to permanent failure over weeks or months.

Sticky or erratic detent feel. The spring-loaded detent mechanism that clicks through each position has worn, and the tactile feedback no longer corresponds reliably to one clean pulse per click.

This is a mechanical wear symptom distinct from the optical failures above, and it often coexists with them in a unit that has seen heavy use.

Any of these symptoms is a signal to replace the encoder before the handwheel fails completely during a critical operation.

Wiring the Replacement — What to Expect

The RE45BA1R5 exits its wiring through the rear of the encoder body. Tosoku does not specify a standard connector on the RE45BA1R5 base model — the wiring terminates in bare leads, and the machine builder specifies the connector and wiring harness in the machine's specific configuration.

When you remove the old encoder, take a photograph of the wiring connections before disconnecting anything.

The wire colour coding typically follows Tosoku's standard output configuration:

• A-phase and B-phase outputs (the quadrature pair)
• A-common and B-common (returns for the two output channels)
• +5V supply and 0V ground

The specific pin or terminal assignments on the machine's interface connector are defined in the machine's electrical diagrams, not by Tosoku — the encoder itself is a standard quadrature output device, and the CNC's MPG interface maps the A, B, and supply pins according to the machine builder's wiring standard.

Consult the machine's electrical maintenance manual for the exact terminal assignments before connecting the replacement encoder.

The C-Suffix Variant in Tosoku's MPG Range

The C suffix on Tosoku RE45B part numbers consistently denotes a minor internal revision — it never indicates a change in the external interface, the performance specification, or the mounting configuration.

This convention applies across the entire RE45B family: RE45BD1R5C replaces RE45BD1R5 (no-dial 5V 100PPR), RE45BA2R1C replaces RE45BA2R1 (80mm dial 12V 25PPR), and so on. Buying a C-suffix version of any RE45B variant as a replacement for the original base version is always correct.

Machine builders and maintenance teams should not be deterred by the suffix update when cross-referencing their BOM part numbers against current stock.

Key Specifications

FAQ

Q1: My machine shows "MPG error" or the handwheel axis does not respond — is the RE45BA1R5 likely the cause?

Not necessarily. Before replacing the encoder, check the wiring from the encoder to the CNC's MPG input — a loose connector, a broken wire in the cable near the panel (where cables flex repeatedly), or a dirty connector pin can produce identical symptoms to a failed encoder.

Unplug and re-seat the MPG connector at the CNC interface board. If the fault clears briefly after reconnection and then returns, the connector or cable is the likely culprit, not the encoder itself.

Only if the cable and connectors check out mechanically and electrically should the encoder be replaced.

Q2: The replacement RE45BA1R5C arrives with bare wire leads — how do I know which wire is which?

Tosoku's RE45B wiring colour standard: Vcc (+5V) is typically the red wire; 0V (ground) is black or white; A-phase output is green; B-phase output is yellow (or similar paired colour scheme).

However, colour codes can vary by production batch and by whether the machine builder specified a custom harness. 

Always verify the wire functions against the original machine drawing or by carefully measuring the voltage relationships before connecting. The A and B outputs will show 5V logic swings during slow encoder rotation; swapping A and B inverts the axis direction but causes no damage.

Q3: The machine builder lists the part number on my BOM as RE45BA1R5 without the C suffix. Is the RE45BA1R5C a direct replacement?

Yes, completely. The RE45BA1R5C is the current production version of the RE45BA1R5 — Tosoku appended the C suffix to track a manufacturing revision that does not change the product's specification, interface, or fitment.

Any authorised Tosoku supplier will confirm this. 

Using the RE45BA1R5C as a replacement for a RE45BA1R5 installation is the correct and expected procedure.

Q4: Can I temporarily test whether the encoder is at fault by swapping in a RE45BA1R5 from another machine?

Yes, swapping encoders between machines of the same CNC type (same supply voltage and MPG input format) is a valid diagnostic technique, provided the wiring connectors match or you can connect the wires correctly.

If the axis that was behaving erratically works correctly with the borrowed encoder, the original encoder is faulty.

If the fault follows the encoder to the other machine, the encoder is the confirmed fault. 

If the fault remains on the original axis with the borrowed encoder, the problem is in the wiring, the CNC's MPG interface, or the CNC parameter settings — not the encoder.

Q5: After fitting the replacement RE45BA1R5, the axis moves in the wrong direction when turning the handwheel. What is wrong?

The A and B phase wires are reversed — either they were swapped in the original wiring, or the replacement was wired with A and B transposed relative to the original encoder's orientation.

Swapping the A and B connections reverses the direction relationship between handwheel rotation and axis movement without affecting any other function. Identify the A and B output wires on the replacement encoder and swap them at the connection point.

Alternatively, the CNC may have a parameter to invert the MPG direction input — on Fanuc controls, this is adjustable via the appropriate MPG axis direction parameter (check the CNC's parameter manual for the specific series).

Either hardware reversal or parameter adjustment achieves the correct result.