VK5RMG UHF repeater Update 17/6/2026:
Nick VK5NJS and myself VK5AC, returned the UHF DR-2X repeater to the Bluff this morning and it is functional again on FM + C4FM and via wires-X from the clubrooms link.
NO actual interference on 146.300 (with a 91.5 tone) was at ANY time measured or detected from this unit and performance was everything it should be.
The only problem detected was the failure of both repeater fans, the mid internal one having an o/c corroded DC cable, and the internal rear one being a random high current failure! This high current caused a SMD control transistor to split in two and let the smoke and carbon particles out in spectacular fashion. Some corrosion on the case body where the rear fan exits, internal fan mounting bracket, internal fan mounting screws and uncovered TX RJxx connectors in the internal fan path, all point to high humidity over a long period of time. I also had a chat to Guy about the problems encountered and his experienced problems. He would be interested to hear of any recurrence or additional information.
Therefore both fans have been replaced and a fan controller installed that has an NTC sensor being bolted to the TX PA. This allows fan control directly related to the TX body temperature.
<=35C = no fans.
>=35C = fans running at 50% speed. (this copes nicely with testing the TX on continuous FM transmission (12 hrs) at either MID or HI power levels, where the fans cycle on/off every 10 minutes approx)
Fan speed ramps up to 100% over the next 10C range.
<= 2C below 35C, fans will turn off.
I have done everything to stimulate and detect the problem, but nothing out of the ordinary occurred!
Best theory is that it was long term heat related, no matter how improbable and impossible this might sound!
The long “War and Peace” version of my notes will be available in paperback soon, or maybe just on the SERG web site 🙂
Maxwell Osmond, VK5AC