Gendex Expert DC Error Err 1: Causes, Diagnosis and Repair of a Dental X-Ray Unit

The Gendex Expert DC is a wall-mounted intraoral X-ray unit with a direct-current (DC) generator, operating at about 65 kV and 7 mA. When it works normally, the display shows the exposure time in seconds, for example 0.320 s. If “Err 1” appears instead, the unit blocks the exposure. This is a protective function, not a random display fault.

According to the manufacturer’s service documentation, Err 1 relates to the power supply: the mains voltage is outside the range the unit accepts (108–132 V for the 120 V setting or 198–253 V for the 220 V setting), or the voltage-selection jumper does not match the actual voltage at the practice. Only when supply and configuration are correct do we look for faults in the unit’s electronics.

The unit is mounted on a wall arm and controlled from the panel on the head. LEDs show the selected tooth programme, patient type (adult / child) and image receptor type, while the arrow buttons change the exposure time. The photo below shows the panel of a working unit with 0.320 s set.

The same message can have several sources. The table orders them from the simplest to those requiring electronics repair. The first two come directly from the manufacturer’s documentation; the rest are typical checkpoints in service diagnosis.

These steps are safe and do not require opening the unit head:

Because Err 1 concerns voltage, the first step is to measure the real voltage at the socket feeding the unit, under load rather than idle. The electrician checks line voltage, protective-earth continuity, loop impedance and the voltage drop when other loads switch on.

A common problem in dental practices is a thin or long supply line shared with a compressor or sterilizer. A 230 V grid fits the 198–253 V window, yet a brief drop during exposure is enough to trigger the error.

When the installation is fine, the engineer moves on to the unit. We follow a fixed order so that parts are never replaced blindly:

The scope depends on the cause found. Often a configuration or supply correction is enough, but sometimes the electronics need repair. Importantly, boards can frequently be repaired at component level without buying a whole module.

An X-ray unit emits ionising radiation, so after any work on the generator or electronics we verify correct operation, including repeatability and accuracy of exposure time, tube voltage and current, and safe function of the exposure button.

Radiation-protection and acceptance-testing requirements derive from Directive 2013/59/Euratom across the European Union and national laws such as the Polish Atomic Law. For units outside Poland we adapt the documentation to local rules.

Our base is Knurów in Silesia, from where we reach practices within about 50 km of Gliwice and Rybnik. For customers elsewhere in Poland and in other European countries we offer remote consultation based on photos and the error description, and repair of electronic boards sent by mail. On-site visits outside Silesia are arranged individually.

Besides the Gendex Expert DC we work on these intraoral units and imaging systems:

Call or write on working days between 8:00 and 16:00 (CET). Prepare the unit model, serial number, a photo of the display with the error and when it first appeared. The more precise the description, the faster we find the cause and plan the repair.