ETX-90RA REPAIR TO DC INPUT JACK
AND TO POWER SWITCH
Last updated: 4 January 2013
Sent: Monday, December 31, 2012 23:06:06 From: ross (email@example.com) Title: If you don't use it you'll lose it! Having bought an ETX-90 that is about eight years old from an elderly lady who didn't quite understand what all the electrical controls and buttons were for, I found that the power circuits wouldn't turn on. I assumed corrosion in the power switch, which may never have been used since new. A quick shot of CRC in the switch did the job and restored power; but only from the external dc adapter. When I pulled the dc plug out, the jack wouldn't switch over to internal battery power, and no amount of poking and prying, putting the plug in and out or spraying CRC would fix it. Eventually, I dismantled the base, (remove the rubber feet, undo three screws and pull the battery cover and base plate off), and removed the RA gearbox, (coupla leads -mark them appropriately, three screws on the worm gear, three more on the gearbox, and it fell out -- sort of), to get to the power board that mounted the power switch, leds, control inputs and dc input socket. Wasn't going to happen. There didn't seem to be anyway to get the board out short of main violence; it seemed to be moulded in place. The upper part of the board was secured by two moulded tangs, the lower was restricted by the base housing flange. It looked like I would have to grind the tangs off to get it out; lots of dust and plastic debris. Hmm! Interestingly enough, it also seemed that the main circuit board for the gearbox couldn't be removed if the power circuit board was still in place. There's probably a knack to it, but I couldn't see it or research an answer; and the forum had no answer - although kudos for the editor's kindly and timely response at an hour when everyone east of the Pacific should have been tucked up in bed. In the end I decided to bypass the switch portion of the dc jack and put in a rocker switch to switch between external dc and batteries. This involved: Cutting a small rocker sized hole with a Dremel in the base and inserting an on/off toggle switch. Stuffing the inside of the base with cloth managed to keep the dreaded grinding dust out. Cutting the negative (black lead) from the battery pack. Re-attaching the battery side of the cut negative lead to one side of the rocker. Attaching a new lead to the other side and, Soldering the other end of the new lead to the solder pad marked '1' on the dc jack (see the image). This is the common negative for both external dc and battery power. The other side of the cut lead isn't needed and can be un-soldered from the circuit board, or just taped up. In this way, when I'm on external power, I flick the toggle to off so that the external power doesn't try to charge the alkaline batteries. When I want battery power only, I unplug the external dc and flick the toggle to on. Bit crude, but it works. Please, anyone trying this should make certain that the pad they're soldering to IS the common negative, or at least, some sort of dc negative. There don't appear to be any fuses in the ETX-90 and directly wiring negative to positive will give a gratifying display of sparks and smells! cheers, Ross Williams Bendigo Australia
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