Allen Bradley you are a swine

Do Allen Bradley try to infuriate you at every turn?

I usually have nothing to do with AB. I rarely come across their PLC’s and I don’t have any of their software. In fact all I know about AB PLC’s has been learned here!

But today I came across an ancient model (SLC 150) running a guillotine. I am sure this is a very old plc as the customer told me he had had the machine for about 20 years.

An output for a solenoid was being erratic and another output had blown a long time ago – could I repair it?

Now at first I was pleased, the terminal blocks just unscrewed and it was 2 minutes work to take it away to my workshop for repair.

Getting down to the relay outputs was something else!!

Every screw, nut and bolt was glued in tight and I mean immovable. There was a massive heat-sink that formed most of the back of the plc but it also wound its way through the pcb back and front with numerous components screwed to it.

The pcb’s were attached together by a flimsy flat ribbon cable that looked like it might break at any point and this also was immovable. I had to work on it in concertina style – gently turning the flailing cards back and forth to unsolder, solder and re-solder.

I had about a hundred separate parts on my bench to refit.

Putting it back together was a nightmare as all the holes had skewed slightly and of course the usual trick happened (to those that repair things)
an important component fell from my grasp, hit my foot and shot off to the black hole that is ‘secret component heaven.’

I am sure you all at one point or other have had this happen; the phrase ‘ where the **** did that go’ is common in these circumstances.

Needless to say, I got all together again, fitted and working and this is just a post to share the anguish and terror we all sometimes go through.

But, I have repaired many models of plc before as output relays are common things that blow.
Usually the output card is nice and accessible, in fact I don’t know of a brand that isn’t.

I hope that later models of AB (especially the brick type) have addressed this jungle of wires and components or do they make it very awkward on purpose?

I have never thought I would be defending Allen-Bradley - which in the PLC world seems to play the role Microsoft plays in the world of PCs...

And yes, SLC150 is a very old and ugly beast; a few years ago I had to modify a program without any documentation, it took me quite a while just to figure out just how to make a branch...

But... you yourself mentioned the nice design of the removeable terminal strips. This is an important observation: the damned thing was designed with the ease of use for a wiring or a maintenance guy in mind.

However, it has never been designed to be repaired on component level by anyone outside of an authorized repair facility. Moreover, I am sure that none of any PLCs, or, for that matter, any other automation components is ever designed for that. You simply replace a failed module and that, in most cases, is cheaper and faster than opening them up and doing some soldering tricks... You would not open up and re-solder a failed transistor in a photoeye, would you? Unless, of course you are doing it for your own amusement or your labor rate is low enough.

Now, in some parts of the world (Eastern Europe comes to mind) this is exactly what is happening. The qualified labor is so cheap that it makes more sense to keep an electronics guy and to have him design and build his own sensor or a regulator board, than to buy one from a company that had spent lots of time and money designing them and making them right. Or, in absense of strong competition (= underdeveloped economy) they think they can afford it.

At any rate, I have never thought it might be like that in UK. If this was your employer, tell him next time that such work is worthless (and you can blame A-B for that ) If you are an independent contractor - charge him all the way! And offer an alternative. It might be hard to find an SLC-150 these days - but a small Micrologix will do the job much better (if you want to stick to A-B, but you don't have to).

And you, instead of doing menial low-life soldering job, would do something more noble, figuring out the original program and converting it into the new PLC... Your stock will definitely go up!

Come and visit

Come and visit my plant Goody

The company that I work for specifies A-B only, nothing else will do.

But we only have 1 SLC 150 still going


The best one I have seen was when another electrician (not me), plugged the round DH+ connector (used on 5/04's etc) into a Micro 1000 - Result 1 dead Micro 1000. He only did it twice before asking for help...

We managed to fix the micro 1000 inhouse (only a blown glass fuse), as the case "pops" apart - no screws...

In defense of the brick.

Manufacturers of "brick" PLCs are all trying to serve the same niche. Low cost, simple limited instructions set, and most of all, no repair. Just take it out, toss it, and put in a new one. Not the best solution to our problems in the world but that is the way many of the industrial items have gone. Look at the HP limit now on the decision to rewind or trash. I remember a time that 5 HP and up was a rewind. Mainly due to the rewind shop being right there in the plant. Anyone have a rewind shop on site anymore? So, AB takes a bad rap from anyone who tries to repair the stuff. AB is not interested in helping the public repair their product, but neither is anyone else really! Just ask your local independent industrial electronic repair depot. Aftermarket is a lucrative piece of business for any company. It helps keep the original new price down a little longer. I have a FORD that is a little over 5 years old and while under warranty it was a gem. After the warranty expired, I have been putting money in the beast on a regular basis. I am no mechanic, but have you tried to work on a late model auto lately? Man, the task is daunting just in trying to locate the thing you need to repair or replace. No wonder auto mechanics make the kind of money they do.

I piece of equipment faithfully served someone without fail for 20 years, and you complain that it was difficult to REPAIR!!!. AB has their faults, but I don't think this is one of them.

LadderLogic said:

However, it has never been designed to be repaired on component level by anyone outside of an authorized repair facility. Moreover, I am sure that none of any PLCs, or, for that matter, any other automation components is ever designed for that. You simply replace a failed module and that, in most cases, is cheaper and faster than opening them up and doing some soldering tricks...

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We replace relays on output cars quite often. Most are not that bad. In fact in the Omrons (C200H) we used to use had socketed relays and a little tool in the back of the module for pulling the old relay. Like you, I would have trashed the 150 in favor of a ML1000. But the original poster does not have access to RSLogix it seems. That is what would keep it from being cost effective to replace.

Well I never, it sounds like a flaming for repairing something rather than trashing it.

Let me say again – I have repaired many many plc cards before and it is quite cost effective as it is usually a short job.

Every one I have done (all brands) has been easy, unscrew the case, unplug the plugs a quick solder job and back working as new.

And I have come across the Omron ones with plug in relays – I thought that was a great idea. So I think your theory of after sales is not quite correct. (or is that just AB)

I did tell the customer that it was very old and it has done its time and I gave him a price for a new plc (Mitsubishi) but seeing as the new program would cost about 20 - 30 times the price of the repair – he plumbed for that for now.
He also thinks I am a gift from heaven that I managed to repair it – I made sure I told him of the difficulties and that I would not be going back in that box in the future.

I don't know how much you are going to spend on that Mitsu?
But you can buy a used SLC like
This One on Ebay
Plug N Pray
Good Luck!

And you, instead of doing menial low-life soldering job

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Was that rude?

There is no doubt that people who dont understand AB lack in a lot of things besides good taste. If AB is equated to Microsoft, undoubtedly they make some of the best the world can buy. I think from the start thread's comments on how the relay was installed on the Output card they did a thorough job for use in an industrial environment, and surely all your comments are only commending of AB rather than exposing their weakness........

Have you worked on their Control Logix controllers, there is no doubt in my mind it beats the competition in all aspects.......

There is always something that can be critiqued, in any product, and there are products made by some of the major brand labels in Europe and the US (far inferior) that definitely dont meet so many standards and yet seem to thrive purely by their weight/lobby......

I have worked with AB for over 15 years, it is like knowing the MS Windows GUI, same thing whatever type of Windows OS you are using..... Other products dont seem to carry the same philosophy.... they are trying to do so now...... AB is pretty consistent atleast for the last 10 years......

Did I further stir a hornets nest here....

Pierre said:

Was that rude?

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It meant to be a joke (there was a smile after all). If it seemed rude - my apologies. I also have to do this stuff once a while...

Ya know, Goody ole pardner, I ain't usually an A-B fan, but I thinks ya is bein' a little hard on them hyar. It ain't quite fair to hold a twenty year old piece of hardware to today's standards for serviceability. It also ain't fair to expect a PLC what was obviously intended t' be an entry level low cost (well, relatively anyhow) t' also be wide open & e-z t' repair. If'n they had put a "No User Serviceable Parts Inside" sticker on it ya would have had fair warning, but even so I don't expect component level repairs on ANY PLC t' be easy, an' I jist don't try t' do it. Like th' man sez: "Ya pays yer money an' ya' takes yer cherce."

LadderLogic said:

It meant to be a joke (there was a smile after all). If it seemed rude - my apologies. I also have to do this stuff once a while...

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I guess I should have put a smile myslef.

Ahem. Ya pays yer money an' yous takes yer cherce...

Working for A-B is like working for the Government or the Church. There's always somebody who's going to be all hot under the collar about something you have no control over but will take it out on you vocally and publicly.

Let me tell you a story that is peripherally about Y2K. The SLC-150 doesn't have a clock so of course it's immune to calendar-related problems. That didn't keep a consultant for BP Exploration from insisting on a formal written statement from me about Y2K compliance on such a unit. I asked him for the precise part number from the unit, so I coulde be concise in my answer.

"I can't read it", was his reply.

Oh, do you mean the label is too close to the side of the enclosure, or has it been smeared or painted over ?

"No, it's shaking so hard I can't read anything but "Allen-Bradley" on the cover." And had been doing so on the North Slope of Alaska since 1986.