Emerson and GE Fanuc / Series 90-30

IC693MDL645 and IC693MDL740 look almost identical on a shelf and one is an input module and the other is an output module. The three digits carry the direction and the voltage, and getting them wrong is the most common ordering error on this platform.

Series 90-30 is the GE Fanuc PLC that ended up everywhere. It is thoroughly obsolete and it is still running food plants, water sites and packaging lines across New Zealand.

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How a 90-30 catalogue number is built

So IC693 is the platform, MDL is discrete I/O, and 645 is which discrete I/O module. Read left to right and an unknown part narrows down fast.

The discrete module numbering pattern

The most useful table on this page. It is a guide rather than an absolute rule, so confirm against the label, but it holds across the common modules.

645 and 740 are one digit apart in the hundreds column and they are opposite directions. On a rack of identical-looking modules with dusty labels, that is an easy mistake to make and an expensive one to discover during a shutdown.

Photograph the rack before you pull anything. It captures every catalogue number and every slot position in one go, and it is the single most useful thing you can send us.

Sourcing and sinking is a real distinction

DC modules come in variants that source or sink current, which decides how the field devices are wired.

A module of the correct direction and voltage but the wrong logic type will not work with the existing field wiring. So the last digits matter as much as the first ones, and this is one of the places where a near-match is not a match.

Send the whole number.

The CPUs

The embedded CPUs are part of the baseplate and the modular ones are not. That changes what a replacement actually is, so establish which you have before ordering.

CPUs differ in memory size, instruction support, communication ports and how many racks they can address. A larger CPU is not automatically a drop-in for a smaller one, because the program has to be compatible with it.

Tell us the CPU number and how many racks the system has.

The battery, and the failure that ends plants

The most important content on this page.

A Series 90-30 CPU holds its program and retentive data in battery-backed memory. When the battery is flat and power is removed, the program is gone.

Change the battery with the PLC powered up, so the memory is held by the supply while the battery is out. Doing it on a dead PLC is how people cause the exact failure they were trying to prevent.

Three habits, all cheap:

Batteries on a schedule, not when a light comes on.

A verified program copy off every CPU, taken while everything works.

Stored somewhere other than the workshop laptop.

Batteries are the smallest order we take on this platform and the one that prevents the largest loss. Ask for them with any other order.

Baseplates, racks and expansion

Regularly underestimated, and a common reason a correct module does not work.

An unterminated or badly cabled expansion rack produces intermittent faults rather than a clean failure. Modules drop in and out, the fault log fills with rack errors, and individual modules get replaced one after another with no improvement.

So on intermittent rack problems, check the expansion cabling and termination before condemning modules.

Slot position matters too. The configuration in the CPU expects a particular module in a particular slot, so a module moved to a different slot faults even though it is the right part.

Analogue modules need their range set

A replacement analogue module arrives at its default setting. So readings that are wrong by a consistent factor after a swap are a range or scaling issue rather than a faulty module.

Check the old module's jumpers or switch positions before it comes off the rack, and photograph them.

Communications modules

A communications module carries configuration, including addresses and protocol settings. A replacement arrives at defaults, so note the settings before removing the old one.

On a Genius network the field blocks hold their own configuration too, which is covered on the brand page. A spare Genius block is not a plug-in spare unless somebody can configure it.

The RX3i path keeps the field wiring

The good news, and it is unusual enough to be worth planning around.

PACSystems RX3i was designed so that Series 90-30 I/O can carry forward rather than requiring the plant to be rewired.

Rewiring is the expensive and risky part of any PLC replacement. It is labour, it happens during a shutdown, and every terminal is a chance to introduce a fault that shows up weeks later.

What carries across depends on your specific modules and rack arrangement. Send us the module list and we will tell you what stays and what does not, which is a useful answer regardless of who supplies the hardware.

Before ordering a replacement

What to send us

The full IC693 catalogue number, all of it.

A photo of the rack. Every number and every slot position in one image.

The CPU number and how many racks there are.

Whether you have the program, and whether it is documented.

Jumper or switch positions on analogue and configurable modules.

Whether you want like-for-like or an RX3i path. We quote both.

What we can supply

Modules. IC693 discrete and analogue I/O across the range, CPUs, power supplies, communications and specialty modules. New old stock, surplus and tested used.

Racks and cabling. Baseplates in both sizes, expansion cables and terminators.

Small parts. Batteries, terminal boards, fuses and covers.

The migration hardware. RX3i CPUs, backplanes and IC694 I/O where a path forward is the right answer.

Everything used is tested before it ships, and we tell you what condition it is in rather than describing everything as excellent.

A sensible 90-30 spares holding

Most 90-30 plants use four or five module types in total, so covering the whole rack is a much smaller order than people expect. Send us the rack photo and we will price the set.

We buy Series 90-30

90-30 holds real value, because the plants running it cannot buy new and replacing the control system is a capital project.

Keep modules with their terminal boards, power supplies with their baseplates, and expansion cables with the racks. A complete rack is worth more than the modules separately, and it is far more useful to the next plant. See Sell To Us.

Common questions

Can you get a part that is not listed on your site?
Usually. The site shows what we hold, not what we can source.

What is the difference between MDL645 and MDL740?
One is a DC input module and the other is a DC output module. They are easy to confuse and not interchangeable.

Can I fit a bigger CPU?
Sometimes. The program has to be compatible, and an embedded CPU is part of the baseplate while a modular one is not.

My PLC lost its program after a power cut.
Flat battery and battery-backed memory. The hardware is probably fine. What you need is the project file.

Modules keep faulting intermittently across the rack.
Check expansion cabling and termination before replacing modules.

Can I keep my I/O and change the CPU?
Often yes, with RX3i. Send the module list.

Do you supply used equipment?
Yes. On 90-30 it is usually the only option, and modules are tested before they ship.

What is the lead time?
Ex stock items ship the next working day within New Zealand. We give you a firm lead time with the quote.

Do you quote in NZD?
Yes, in NZD including GST for New Zealand customers.

Related

Emerson and GE Fanuc overview, including the badge history, the Genius I/O warning and the Fanuc CNC distinction.

For comparable legacy PLCs see Siemens S7-300, Allen-Bradley SLC 500, Modicon Quantum, Omron CS1 and Mitsubishi Q.

Send us a photo of the rack

It captures every catalogue number and every slot position at once, and it is faster than typing them out. And ask about batteries while you are at it. Quotes in NZD including GST.

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Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Emerson, GE or Fanuc. Emerson and PACSystems are trademarks of Emerson Electric Co. GE and GE Fanuc are trademarks of General Electric Company. Series 90 and Genius are trademarks of their respective owners. All trademarks, brand names and catalogue numbers are the property of their respective owners and are used here for identification purposes only.