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DMR-203 Drop-Out Fault

This dmr-203 drop-out fault was one of the strangest ones I’ve seen for a while, as it took so long to solve it deserves a place in the knowledgebase.

The system; VTX-75-24, DMR-203, Spektrum DX radio

The symptoms; The engine ran fine up on blocks with no load, but when load was applied the controller shut down until the whole system was re-started.

What was it; The DMR-203 ignition had been wired up using a latching relay on a spare radio channel. The relay had 2 modes, latching and non-latching. In latching mode there was an interaction that switched off the DMR-203 whenever a drop in the battery voltage was detected [from 12.5 down to around 12.2V]

Solution; Switching the relay to non-latching mode solved the problem.

I wasn’t able to investigate further to see if this was due to a faulty relay, part of it’s specification, or due to the RC power supply.

The relay was an unbranded one from ebay and looked like this…

latching relay that caused problems