Epson 1390 DTF White Ink Circulation Pump Not Running: How to Diagnose the Pump, Timer, and Driver Circuit

Question

I purchased a modified Epson 1390 DTF printer, but the white ink circulation system does not work. The white ink pump is not running, so the ink cannot circulate. I suspect the timer or pump driver circuit may have failed. Unfortunately, the supplier did not provide a manual or setup instructions with the modified printer. How can I determine whether the problem is the pump, power supply, timer, or driver circuit?

Answer

Start by Measuring the Voltage at the White Ink Pump

Your suspicion about the pump driver or timer circuit is reasonable, but I would not replace the timer or controller until you have measured the voltage going to the pump.

The first diagnostic question is very simple:

When the circulation system is supposed to be running, is the correct DC voltage actually reaching the pump?

Before measuring anything, look carefully at the pump itself and find its rated voltage. Do not automatically assume that an Epson 1390 DTF conversion uses a particular voltage. The Epson 1390 was not originally manufactured as a DTF printer, so the circulation system, pump, timer board, white ink tank, and associated wiring were added by the company that performed the conversion. Different conversion manufacturers can use different components.

DTF circulation pumps are available in different voltages, including 12-volt and 24-volt configurations. Therefore, check the label on the pump, controller, and power supply before applying voltage or making measurements. BCH Technologies, for example, has worked with both 12V and 24V white-ink pump configurations, so the printer model alone does not tell you which voltage your particular conversion uses.

If the pump says DC 24V, for example, you would normally expect approximately the specified DC voltage across its terminals while the controller is commanding it to operate. If the pump is rated for another voltage, use that specification instead.

If Correct Voltage Reaches the Pump but the Pump Does Not Run

If you measure approximately the pump's rated voltage directly across the pump wires while the circulation system is supposed to be active, yet the pump does not turn, the problem is much more likely to be the pump itself than the timer.

Several failures are possible.

The pump motor may have burned out or developed an open winding. The motor may also be mechanically seized. On a peristaltic pump, the rollers or pump tubing can sometimes become difficult to turn, creating enough load that the small DC motor cannot start.

There could also be an internal connection failure where the wires enter the motor.

If you are electrically experienced, you can disconnect the pump from the controller and test it independently using a properly regulated DC power source that matches the pump's rated voltage and polarity. Never apply an assumed voltage to an unidentified pump.

If the correct voltage is present and the pump still will not operate, replacement of the pump is usually the next thing I would investigate.

If There Is No Voltage at the Pump

If you measure zero volts, or substantially less than the expected voltage, then move backward through the circuit rather than immediately blaming the pump.

The next components to investigate are:

• The pump wiring and connectors

• The timer/controller output

• The controller's power input

• The DC power supply

• Any fuse protecting the circulation circuit

• A relay, MOSFET, or transistor used to switch the pump

• Broken solder joints or damaged traces

• Loose or reversed connectors

• Failed switches or enable connections

The objective is to determine exactly where the voltage disappears.

For example, if the controller receives 24V but sends 0V to the pump during a period when the pump should be running, the pump is probably not your first suspect anymore. The timer/controller or its output switching circuit deserves closer examination.

On the other hand, if there is no power reaching the timer board in the first place, replacing the timer will not solve the problem. You would need to trace the circuit farther upstream toward its power source.

Check the Input Voltage to the Timer or Pump Controller

Suppose the pump receives no power. The next measurement I would make is at the timer/controller's DC input.

You are essentially looking for this sequence:

Power supply → timer/controller → switching circuit → pump

If the correct voltage is entering the timer/controller but nothing is coming out when the circulation cycle should be active, there may indeed be a timer or driver problem.

However, if there is no voltage entering the controller, the failure is somewhere before the controller.

This distinction is important because otherwise it is very easy to start replacing components unnecessarily.

The Timer May Not Be Designed to Run the Pump Continuously

There is another possibility that can easily cause confusion: the pump may not be intended to run continuously.

Many white ink management systems use a timer that periodically turns the circulation pump on and off. Therefore, measuring the pump during an "off" period could make a properly functioning system appear defective.

You need to determine whether the controller has adjustable settings such as:

ON time: how long the pump operates.

OFF time: how long it waits between circulation cycles.

Some timer systems may run the pump for a short interval and then leave it off for considerably longer.

Since your supplier did not provide the setup manual, identifying the controller board or timer model may help. Look for a model number, manufacturer name, voltage marking, terminal labels, or other identification printed on the board.

Photographing those markings before disconnecting anything is also a good idea.

Check Whether the Controller Has a Display or Indicator LEDs

If your timer/controller has LEDs or a digital display, they can provide useful information.

For example, determine whether:

• The controller powers up.

• Its display illuminates.

• An output LED changes when the pump should start.

• The timer is actually counting.

• The controller enters an ON cycle.

• The pump output voltage changes with the indicator.

Suppose an output LED turns on but no voltage appears at the pump terminals. That could point toward a damaged output transistor, MOSFET, relay, connector, or circuit trace.

If the controller itself is completely dead, check its incoming supply before condemning the board.

Check the Pump Directly Before Replacing the Driver Board

One of the most useful ways to divide this problem is to test the pump separately from the timer.

Again, this should only be done after positively identifying the pump's rated DC voltage and polarity.

If the pump operates normally from an appropriate external DC source, you have established something very useful:

The pump itself works.

You can then concentrate on the controller, timer, power source, wiring, or switching circuit.

If it does not operate from the proper external power source, there is little reason to troubleshoot the timer until the pump problem has been addressed.

Check for a Mechanical Blockage Too

An electrical problem is not the only possibility.

If this is a peristaltic pump, inspect the pump tubing and roller assembly. Dried white ink, hardened tubing, pinched tubing, incorrectly installed tubing, or excessive resistance can prevent the pump from turning normally.

White DTF ink contains a large amount of pigment compared with ordinary dye ink. Maintaining movement is important because the pigment naturally tends to settle. A failed circulation system therefore should not be ignored for extended periods.

However, avoid running a circulation pump aggressively simply to "force" a clogged system open. Excessive pressure in a poorly designed circulation path can introduce other problems at the dampers and printhead.

Do Not Assume the Epson 1390 Mainboard Controls the Circulation Pump

This is particularly important with a modified Epson 1390.

The original Epson 1390 does not contain a factory DTF white ink circulation system. Therefore, in most conversions, the white ink pump and its timer/controller are an additional electrical system installed by the DTF converter.

In other words, the Epson mainboard may be working perfectly while the aftermarket circulation system is completely dead.

That is why I would troubleshoot the white ink system as its own circuit first rather than immediately investigating the Epson mainboard.

A Practical Diagnostic Sequence

If I had this machine on the bench, I would approach it approximately this way:

1. Identify the pump's rated voltage and polarity from its label.

2. Identify the circulation controller or timer's required input voltage.

3. Turn on the system and verify that the timer/controller receives its required DC input.

4. Determine when the controller is supposed to command the pump ON.

5. During that ON period, measure DC voltage directly across the pump terminals.

6. If correct voltage is present but the pump does not turn, investigate or replace the pump.

7. If no voltage reaches the pump, measure the controller's output.

8. If the controller has proper input power but no output during its ON cycle, investigate the controller, relay, MOSFET, transistor, or other switching circuit.

9. If the controller has no input power, trace backward toward the power supply, fuse, connectors, and wiring.

10. Inspect the pump and tubing for a mechanical blockage before concluding that the failure is entirely electrical.

This approach prevents you from replacing the timer, pump, and power supply by guessing.

Be Careful When Taking Measurements Around Ink

Because this is a DTF printer, there is another issue to keep in mind: you are working with liquids around low-voltage electronics.

A multimeter slipping between terminals can create a short circuit. White ink or cleaning solution reaching connectors and circuit boards can also cause corrosion or electrical damage.

Keep the meter probes controlled, avoid accidentally bridging adjacent terminals, and disconnect power before unplugging or reconnecting wiring. If you need to make resistance or continuity measurements, those measurements should normally be performed with the circuit powered off.

Also, never connect a pump directly to an unidentified power source just to see whether it spins. Verify the voltage and polarity first.

Why the Missing Manual Makes This More Difficult

Unfortunately, because the Epson 1390 was modified by a third-party supplier, there is no universal Epson service procedure for this particular circulation system.

The seller chose the circulation pump, timer board, wiring layout, ink tank, and possibly the driver electronics. Two Epson 1390 DTF conversions can therefore look very similar externally but have entirely different white ink management circuits.

That is why measuring the system is more reliable than assuming how it was designed.

If you can identify the timer/controller model from markings on the circuit board, searching that exact model number may also help you locate its operating instructions and determine how its ON/OFF timing is programmed.

Printer repair and DTF modification problems can be complicated because so much of the diagnosis depends on physically inspecting, measuring, and testing the machine. For that reason, we're unable to provide individual remote troubleshooting, repair guidance, or ongoing technical support for printer repairs. We do offer an in-person evaluation and repair service through our BCH Technologies local diagnostic facility [https://bchtechnologies.com/printer-repair-service]. Due to high demand, the service operates on a first-come, first-served basis, and it may take several weeks before an appointment or drop-off becomes available. Our services can cover either a complete printer or certain individual parts, with instructions provided for the applicable service. We also recognize that professional repair may not be the most economical choice in every situation, so we strongly encourage self-help and online research when practical. A good starting point is YouTube or the BCH Technologies YouTube channel [https://youtube.com/@bchtechnologies]. On our channel, use the search icon near the "About" section to search for the exact printer model, component, or symptom. We have produced repair videos for more than nine years, and with such a large library, I cannot always remember which specific video covers every individual problem. YouTube's search function is normally the fastest way to locate the relevant material, and it may also recommend useful videos from other creators.

Thank you again for contacting BCH Technologies and for taking the time to explain what is happening with your Epson 1390 DTF conversion. I hope these measurements help you narrow the problem down to the pump, power supply, wiring, or timer/driver circuit instead of having to replace components by trial and error. We truly appreciate your continued support and engagement with our technical content.