Mitsubishi FX1s PLC
Andy Martin
Tuesday 19th August 2025
At Martronic, we understand that machinery needs to run, and to have a piece of critical machinery offline is an absolute no-no.
We had a call from a customer in the stainless steel industry with a fault on a feeder control panel. The HMI had lost communications with the PLC, but the machine could still be operated and was still producing.
We took a trip to site to have a look at the panel, inside it was a Mitsubishi Electric FX1s PLC and a GOT1000 HMI. We couldn't ascertain which item was at fault so we agreed to take both items back to the workshop Friday afternoon once the site shut. This gave us a weekend window to carry out the repair.
We got straight to work and uploaded the HMI project using E Designer. We always upload PLC, HMI & drive files where possible as it ensures if the worst happened we could reprogram a new unit. The issue arose when we came to upload the PLC, we just couldn't establish communications. The realisation then hit that this was probably the underlying issue and the reason the HMI is offline. We reflowed the entire PLC and communications then sprang into life which was a relief as component suppliers had now closed.
We uploaded the PLC project, and purchased a new PLC as a spare, as this was now very old, and the microprocessor pins were covered in epoxy resin so it was not worth the risk to attempt any further work.
They are up and running now, with the new PLC on its way ready to program and drop back in.
All in a weekends work, with zero disturbance to production 👌
Do you have some critical PLC's and require repair? Or simply just a visit to back them up? If so drop us an email to see what we can offer.
Profibus Termination FAQ's
Andy Martin
Tuesday 5th August 2025
A question I get asked frequently is should profibus termination resistors be turned off or on?
Purpose of Terminating Resistors:
Profibus uses a twisted pair cable with a specific characteristic impedance. Terminating resistors (usually 220 ohms) are placed at the ends of the bus to match this impedance and absorb signal reflections.
Signal Reflections:
Without proper termination, signals traveling along the bus can bounce back when they reach the end, creating interference with subsequent transmissions and potentially causing data corruption or communication failure.
On or Off?
It really is quite simple how to work this out. Profibus is a node to node network where the cable enters the connector and then leaves on its way to the next device on the network (2 cables in the connector). There will be 2 defined points where the cable enters but doesn't leave (only 1 cable in the connector). These are the ends of the network.
The end devices on the network should have the termination resistors ON, all the others should have the resistors OFF.
If you experience communication issues on your Profibus network, checking the terminating resistor switches is a good first step. Make sure they are set correctly as per the topology of your network
Siemens LT Module Repair
Andy Martin
Thursday 24th July 2025
A factory in Belfast contacted us after they were having an issue with their press. The press was a large punching machine which perforated sheet metal on a reel. It had an automated feeder which fed the material into the press in accurate lengths. This feeder was servo controlled using a Siemens 611 drive, motion control card and 1FT6 servo motor. The drive would randomly go into fault when running and would give no indication other than a red light.
We suggested that the LT module and control card were removed for servicing back in our workshop. We made the right decision as when it was dismantled we found several issues. The power supply on the control card had bad capacitors causing an unstable 5V rail, and the LT module had cracked solder joints on the power pins which were a ticking time bomb before they got worse and led to arc damage.
Both items were dismantled, fully cleaned, serviced, reflowed and conformally coated. Once finished they looked like new which is testament to the standard Martronic work to.
They were shipped back on an overnight delivery and the machine went straight back into production.
Delta Inverter Repair
Andy Martin
Tuesday 17th June 2025
It isn't always just about fixing a fault, it's taking the time and effort to work with a customer to ensure the item goes back to site and works for a long time to come.
Take this Delta Electronics inverter, its nothing out the ordinary. A decent 11kW variable speed drive, well made and reliable. Have a look inside it - it has quality Nichicon branded capacitors, the boards are conformally coated and the power interconnections are all quality metal components. The more eagle eyed amongst you may see something which isn't quite right, and you would be correct in noticing an area of the board is extremely burnt.
The customer rang me this morning, a little perplexed as this drive was brand new off the shelf and upon fitting it blew instantaneously, belching out smoke into the panel. Obviously this isn't what should happen, and the first thing we think is its either defective from new, or there is an external issue. My money is usually on an external issue as these inverters have a great reputation for reliability.
Upon discussing this issue, we took a trip to site to have a look at the damaged inverter and also the panel. As soon as the door was opened I knew exactly what had happened. Connected to this inverter is a DC bus brake chopper unit. I couldn't be sure until I got my multimeter out but I could have bet my bottom dollar the resistance across the DC supply leads being low. It was. The chopper had gone short circuit resulting in the 36 ohm braking resistors permanently being connected across the DC bus. This meant that when the drive was powered on there was a massive stress on all the input circuitry which never disappeared, and sooner or later something has to give.
The inverter is back with us now for repair, and the braking module will be following. It took a little time out of my day to do this but the end result paid dividends and saved another new drive failing instantly on power up. It would have been easy enough to take the drive away, fix it and just ship it back but that isn't what we are about. In a few days this drive will be repaired and back on site, with 100% confidence it will work as expected.
Indramat DDS Servo Drive
Andy Martin
Monday 23rd June 2025
This Indramat DDS2.1-W150 is in the workshop this week with a F61 error which relates to an abnormality in the current drawn from the power stack.
These drives were massively advanced for their time when they came out and are still widely used today as axis drives in CNC machinery. They build on the basic performance of the TDM analogue drives adding in digital support for an endat encoder as well as communication control using plug in cards.
We dismantled the drive and found some components in the current sensing circuitry at fault and these are being refitted tomorrow. Once rebuilt we will connect this to a TVM power supply and run it up with its MDD servo motor.
We don’t just fix faults at Martronic, we fully test everything ensure you have no surprises when your repair comes back to site.
Siemens OP17 HMI
Andy Martin
Tuesday 1st July 2025
With any electronic devices we always recommend routine maintenance and servicing to avoid costly breakdowns. This can be a simple visual inspection, cleaning or replacement of common time degradable components.
This Siemens Operator Panel OP 17/DP12 6AV3617-1JC30-0AX2 is a classic example of being left to do its job since 1997 without any maintenance.
You would be right in thinking “What maintenance does a keypad screen really need?”, however when the covers are removed the implications of no maintenance become quickly apparent. This unit was behaving unpredictably and not accepting input of data from the keypad. The initial thought was maybe a failing keypad however this is functioning fine after testing each of the switches. The real issue is the result of a leaking supercapacitor. The function of this capacitor is to retain data in RAM when the machine is off, and ensure the time and date remains correct. This one isn’t behaving like a supercapacitor anymore, more like a super resistor being almost completely open circuit with no capacitance. During its final years it has leaked electrolyte over the PCB in turn damaging traces, vias and neighbouring components.
We have ordered some new capacitors and also replacement logic ICs which decode the keypad matrix data as the legs are all corroded. We are now cleaning the board and repairing the failed vias which connect the top of the board to the underside.
Once we are happy the repair is complete we will connect it to our Siemens PG and run a test program to ensure everything works.
If you have any concerns over your equipment why not let us visit site and offer free advice on critical assets? There isn’t much we haven’t seen and simply opening a panel door can usually be enough for us to put together a plan of high risk equipment.
