Ol_Johnny

SLC-500 Power Supply Short?

7 posts in this topic

Anyone have experience with the old SLC-500s?

I have one machine that is about 13 years old and I think they used a new old stock SLC-05/04 when they built it.

Anyway I had a battery error, which makes sense since the battery was very old, and I lost my program when I tried to replace it, which makes sense because the capacitor which is supposed to hold the charge is very old.

When I tried to re-download the program to the PLC, I could not connect, I realized my issue now was no null modem... and my driver not working on my RS-232 to USB converter.

My question is:  What is the port above the DB-9 port used for?

It was labeled PROG, so when my DB-9 serial cable didn't work I tried a serial cable for a mitsubishi FX series on the top port... and.... my power supply died.

Is this a common thing on SLC-500 power supplies?

Can you short them by using the wrong cable?

The weird thing is the fuse on the front was not blown.

Is there a fuse inside I can get to and replace?

We are planning on just keeping this machine a few more years so we don't want to upgrade it.

The CPU was fine afterwards.

Image result for SLC-05/04

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The round mini-DIN connector and the 3-pin Phoenix connector are both connected to the Data Highway Plus (DH+) communications port. It takes a special adapter to communicate through that channel.

The Rockwell adapter is 1784-U2DHP. In our experience, it's very expensive and not very robust. We've had several fail in normal use. ProSoft makes a gateway module as well, the AN-X2-AB-DHRIO. We've found the ProSoft module to be a lot more robust and cost effective, but it requires an external power supply and is a little more cumbersome to configure in RSLinx (not bad at all, just not as easy as the U2DHP).

I'm a little surprised you damaged the power supply but not the CPU. You may have killed the DH+ port without affecting the rest of the CPU. I'm not aware of any additional protection inside the power supply, just the fuse on the front.

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Hey thanks for clearing this up for me!

I'm still fairly inexperienced in serial communications and there are so many protocols out there.

Thank goodness Ethernet and USB are becoming so ubiquitous.

Yeah it was weird that the power supply stopped working... maybe it was dying anyway.. and that's why the battery error tripped and the capacitor didn't hold its charge.

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Given the age of your system, I wouldn't be surprised if the power supply was already going.  They can die in weird ways and one of the things that can happen is that the PLC will drop the program.  Not real fond of the SLC power supplies as they can cause pain and suffering.  They don't seem to just die and that's it.  Every one I've dealt with caused weird problems such as program drops that went away when the power supply was changed.

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DH+ uses an oddball voltage if you connected a computer's serial port to it you're lucky it didn't burn up your serial port as well.

Odds are that port on the PLC is now dead.

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I've had similar experiences as PLCMentor with the SLC 5/xx power supplies. They can cause the PLC to randomly dump its program and can also cause it to fault, thinking that a module is failing. I've seen it where we replaced each module one at a time (the fault code couldn't identify which module it was) until replacing the power supply fixed it. I've had similar behavior caused by the chassis.

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In my early days, I unknowingly grabbed a crossover ethernet cable , then plugged it into a 1747-PIC and a SLC 5/03's DH-485 port.  It killed the power supply and erased the program.  We unseated and reseated the processor and power cycled the machine, reloaded the program and everything was good.  Even the DH-485 still works.

Edited by Twigums

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