EUROTHERM 3504 Process Controller Repair

They are designed to control industrial and laboratory processes via input sensors which measure the process variables and output actuators which adjust the process conditions. 3504 controller can handles input types of Digital inputs, Thermal couple inputs, Pt100 inputs, 0-20mA analog inputs and many more. if you interested about full description, datasheets are available from manufacturers website.

I received this unit for repair in full dead condition. there were no any physical damage. After removing the cover, i did not see any visible damage on the board. 

There  were very complex board arrangement inside. i had to carefully disconnect and remove all boards to test components of main power supply.

Testing procedure starts from AC line input. fuse, NTC and filter capacitors were fine. DC bus had 320V DC. but secondry side seemed dead. no voltage across filter capacitors at all.

I tested supply voltage rails of SMPS switcher. that also showed 0V. but that can't be happen, because DC bus must provide starting supply voltage to switcher. I had to manually inject voltage to switcher and found 47uF filter capacitor getting heated.

47uF capacitor was the problem. that had an internal short circuit.

 

replacing the capacitor solved the problem.

* Use good spare parts. remember, build trust. trust builds businesses. saved cents do not. * 

8X32 LED Matrix controller

 

Frame by frame animation can be played in this module. animations can be created using LED Matrix studio or manual pixel editing. pixel binary file then be uploaded to the board using a PC software.

MTXProg software is the interfacing software for LED Matrix controller board. www.epsiconlabs.com is no longer available. OptimMachines and OptimRepairs are formerly Epsicon Labs.

Board Documentation - Download Technical Documentation

Download Software (FREE FOR USE) - Windows XP or Advanced versions

If you wish to get more details about boards, please comment.....

Programmable cylinder welder controller

 

This device was designed and built by me to ease the welding process of cylindrical surfaces. User can start/stop the welding torch along the way during welding. cylinder rotates while the torch remaining in a fixed position. user can record the welding macro to automate the process.

There are fixed number of steps to cover up full circumference of the cylinder. therefore we can calculate where to start/stop the welding torch during the cycle.

How to teach the controller.

First, user must switch the device into record mode. then user can operate the device to record the procedure of welding. device has COPIED the every step of  operation. from the second work piece, user can PASTE his recording endlessly.

if you want more information about the device, please make a comment. 

ZNC-1500C CNC Flame cutter repair

 

I was requested to visit the customer’s factory to inspect a flame cutting machine that was reported to be malfunctioning.

According to the customer, several control panel buttons were unresponsive, affecting normal machine operation. Additionally, when attempting to set a specific cutting length, the machine head failed to stop at the programmed position. Instead, it continued moving beyond the desired point.

Preliminary observation suggests that the stepper motors may not be holding (locking) properly at the commanded position, which could indicate a possible issue within the motor driver circuit, control signals, or the power supply to the motion control system.

After removing the cover, i observed that there was iron dust all over the internal parts of the machine. therefore i started to clean one by one.

 

 

 

Upon detailed testing of the control system, all four relays on the relay board were found to be malfunctioning and operating unreliably. These relays were affecting proper switching and control functions of the machine.

In addition, approximately twenty control panel push buttons were identified as defective or intermittently unresponsive, requiring replacement to restore reliable user input operation.

All identified faulty components were serviced accordingly. The relay board was repaired, and the malfunctioning buttons were replaced. Following these corrective actions, the system was restored to proper working condition.

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45A HAAS servo amplifier repair

 

These types of device is used to convert 320V DC bus into three phase AC for drive a motor. this device is not a VFD. it doesnot provide driving frequency. Servo amplifier has an interface to receive the drive signal from the external source. board has a red "Fault" indicator for display any fault that encountered during operation.

Reported Symptoms

A Haas 45A servo amplifier was received from the customer with an intermittent fault condition.

Upon initial power-up, the servo amplifier started normally and indicated proper operation with the green status LED illuminated. The unit appeared to function correctly during startup and initial operation.

However, after running for a period of time, the amplifier entered a fault condition. The green status indicator turned off and the red error LED illuminated, indicating a system fault. The issue was not immediate at power-up but occurred after some operational time, suggesting a temperature-related or load-dependent fault condition.

Repair Procedure

Upon receiving the unit, an initial functional test was carried out by powering up the device. The green status LED illuminated, indicating that the system was receiving input power and entering its normal startup state.

Next, all primary power supply rails and regulator output voltages were measured. At this stage, the readings were within expected limits, and no abnormalities were observed.

To further investigate potential intermittent or temperature-related issues, controlled heat was applied to the PCB using a hot air gun. After approximately 10 minutes of gradual heating, the fault condition was triggered and the red fault LED illuminated. This confirmed the presence of a temperature-dependent failure.

Following the fault indication, the regulator output voltages were measured again under the heated condition. At this point, a voltage fluctuation was detected in the 5V supply rail.

Inspection confirmed that the 5V LDO regulator was malfunctioning under thermal stress, leading to the fault condition. The regulator was identified as the defective component requiring replacement.

Actually, replacing the LDO solved the problem. 

LDO is used to step down 15V into 5V for power up the CPLD and Microcontroller. op-amps are driven by 15V.

 

ATX Power Supply repair

 

An ATX like industrial power supply received for repair. after some basic investigations, it was actually a ATX power supply with 24V power rail. Power supply came with complete dead condition.

 

Structure of this type power supplies,

                                                   Total power supply consists of two separate power supplies. one is used for stand by supply and other is used for power delivery. Main power supply can output +3.3V, +5V, +12V, -12V, +24V. Circuit used for supply stand by power can deliver +5V with maximum 2A. Stand by supply was driven by TNY267 power converter ic. which is all in one(built in power mosfet) package.

Since these PSU's have two separate power supplies, you can separately switch on each other. If stand by supply is not working, sometimes main power supply may work. The PSU i got is mostly similar to the model : API3PCD2-Y01, two switch forward power supply. I cannot publish it here because of copyright reasons. but you can download it from the web.

manually switching the main power supply on is a smart idea when all things may go as expected. but it can be disastrous if SMPS switcher or gate driver has a fault.

According to the circuit, supply needed to run secondary switcher (UC3843) was taken from secondry winding of stand by power supply. therefore we have to use separate power source to power up. 

Remove main switching MOSFETS from the board. test them using multimeter. you can manually power up the switcher now (emitter pin of Q4 is better). use the bench power supply and set to 12V, 600mA range. inspect output waveform of switcher using a oscilloscope. frequency must be in kHz range and peak voltage must be at least 12V are signs of good switcher.

Lets turn to the primary stand by power supply. Connect main power to the PSU. always use a series lamp for safety. Check voltage between source and drain pin of the ic(TNY267). must be 300~320V DC( testing on 230V AC). check voltage value of C54. if it has stable value of nearly 15V, switcher is fine. if it has some unstable value, check related components. if it doesnot have any value (0V), replace the switcher ic.

I was able to repair the power supply by replacing TNY267. however i replaced UC3843 also.  

brown liquid is an insulation material used to protect board from moisture and dust.

1.5kw TOSHIBA three phase inverter drive (VFD) repair

 A Variable Frequency Drive (VFD) was received for service with a complaint of dim display and inability to control motor speed. The customer reported that although the unit powered on, the display was barely visible and the speed adjustment function was not responding properly.

First inspection of the machine, I found corroded PCB's covered in dust.

 

HOW TO TROUBLESHOOT SUCH A MACHINE
 

Very important. Before start the repair, you must make sure that the device is repairable. time is money. don't invest your time on irreparable things.

How to test repair ability,

Check if it has a microcontroller,FPGA or any programmable device. Download the datasheet. diode test on all pins. Check supply rail impedance. Power up the IC, 1V below the rated supply voltage from bench power supply and check drawn current. Check the ic temperature.

If diode test fail on some pins. isolate them from other connections and test again. if you have the datasheet, check for internal connections. if diode test fail and you found internal short circuit to ground. you have to replace the microcontroller. Find the firmware and re-program a new chip will be impossible because most manufacturers do not publish their firmware. therefore repair will be impossible.

Supply rail must have at least 20ohm. if supply rail impedance is too low, check for parallel resistances. cut PCB + path to ic and test again. if ic continuously shows low impedance, it may have shorted to the ground. therefore repair may be impossible.

If ic gets heat after power up and heat rises continuously, replace is the option. Replacing is impossible if you don't have resources.

if ic draws less current and heat is normal, power it up at the lowest rated voltage as described in the datasheet. measure crystal oscillation using an oscilloscope.

If crystal runs. good point. move into other parts. MOSFET,Op-Amp, gate drivers,etc... because these are replaceable. you have some certainty that replacing such part will solve the problem. 

I was able to repair the VFD. problem was the corrosion of PCB motherboard caused by some liquid or something. Some SMD resistors had dry joints with the PCB. i have cleaned the PCB and replaced all corroded parts. finally it came back to work. 

Replacement PCB board for Icecream Machines

 

Internal Working Principle of the Ice Cream Machine

The ice cream machine operates using two primary mechanical systems: the refrigeration system and the mixing system. Each system is driven by an independent motor designed specifically for its function. One motor drives the compressor within the refrigeration unit, while the other drives the mixing mechanism.

The refrigeration system, powered by the compressor motor, is responsible for removing heat from the ice cream mixture. As the temperature decreases, the mixture begins to solidify. Simultaneously, the mixing system continuously agitates the mixture to ensure uniform cooling, prevent ice crystal formation, and maintain a smooth texture.

An important aspect of the machine’s operation is its method of detecting the consistency (thickness) of the ice cream. Instead of using a dedicated viscosity sensor, the control circuit monitors the current drawn by the mixer motor. As the mixture thickens, mechanical resistance against the mixer increases, which in turn increases the motor’s current consumption.

The user can adjust the desired thickness of the ice cream by setting a predefined current threshold within the control circuit. When the mixer motor current reaches this preset cutoff value, the system interprets this as the ice cream reaching the desired consistency. At this point, the machine stops the freezing cycle and indicates that the product is ready for dispensing.

This current-based control method provides a simple, reliable, and cost-effective way to determine product readiness without requiring complex sensing hardware.

Types of boards currently in production,

 Maximum 4A mixing current.

 Maximum 6A mixing current.

 Maximum 15A mixing current

Please comment if you interested and I can provide all technical information about above boards.

Programmable LED sequence controller

 

18 pre programmed patterns to select.

User can select one or more patterns to run.
Running speed can be controlled.
Pattern loop count can be edited.
50 slot pattern memory.

Complete introduction about this board are provided. you can download them using following links.

User manual - Download user manual

Technical manual - Download Technical manual with schematic

Firmware source code - XC8 source code

 

How to program and operate the module,

TAYOR WSM-250I inverter tig welding machine repair

A customer brought in an inverter-type welding machine TAYOR WSM-250I with a complete “no power” condition. The unit showed no LED indication, no fan operation, and no output response when connected to mains supply. This document describes the systematic diagnostic process and final repair solution.

External inspection showed no visible mechanical damage. However, upon opening the unit, the circuit boards were covered by dust layer. I had to clean the unit before testing for any fault. Later i observed that the main fuse for logic board power supply was open.

Shows internal circuit of the welding machine

Diagnostic procedure,

                                    There are precautions to take before power up or insert power to these types of machines. the conventional lamp series method will not work for this type circuits. Bulk capacitors hold enough energy to blow up the mosfets when you accidentally trigger high side and low side mosfets.

STEP-1

Disconnect main DC bus from bulk capacitors. some manufacturers provide jumpers on the PCB for that purpose. otherwise you will have to cut the pcb gently. this will protect your mosfets.

STEP-2

Now you can use lamp series method to power up the primary power supply. primary power supply delivers power to display panel, MOSFET or IGBT gate drivers, inverter driver board and relays.

**The primary power supply of this WSM-250I machine was the fault. SMPS controller ic and Power mosfet was burned. I was able to bring it back to life replacing those parts.**

STEP-3

After working on primary power supply, inspect inverter MOSFET gate waveforms from PWM generation ic (SG3525,TL494,etc....) using a oscilloscope.

STEP-4

Now you can connect capacitors into the DC bus and power up the machine.

This is the very basic explanation on how to diagnose inverter type welding machines. please check following components before you move into the deep of the circuit.

• Power cable, fuse inside the plug
• VDR
• NTC thermister
• Bridge rectifiers
• Power Relays
• Schotkey diodes
• Capacitors in primary PSU