DNO Fault Finding Guide

This is the fault finding guide for the DNO range of controllers.

The DNO is the end result of a long line of 4QD analogue controllers including the NCC and VTXs. It is therefore a well proven and reliable circuit and many thousands have been in use for many years. This page is to help identify and solve any problems that may occur.

There is a fault finding sheet here which lists a number of key voltages to measure. We recommend printing this off and recording the voltages listed as this often gives a good indication of where problems are.

Other issues that we know about are…..

  1. Tripping out / condensation. The DNO has a current limit trip circuit, when the current exceeds a set limit for 17 seconds the controller will switch off and require an off / on reset to restart operation. The current trip circuit uses a pair of transistors in a high gain configuration to perform the trip operation, and this circuit can be susceptible to moisture or condensation on the circuit board. When this occurs the DNO will run for a short period but then stop responding to the throttle. The problem only seems to occur when the DNO is subjected to a sudden temperature change with high humidity levels. It can be cured by applying conformal coating to the components outlined in red below.  RS supply 15ml bottles [part number 321-7324]. This was included in production from March 2021.

condensation protection













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