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Have a couple of Topcon 302D total stations and on one of them the EDM is failing.  It works fine some days, and then other days when I press "measure" it just waits like it is not getting a signal.  Seems to work better with 100% full battery but after about  10 minutes  of use it starts not wanting to read again.

  Brought it in to be checked out but they said it needed a new EDM board for $1600.  I can buy another used instrument for about the same price, so I did not fix it. 

  I have quite a bit of background in fixing electronic things (CNC machines, controllers, etc.) and have a digital scope, test instruments, etc.  However, without any prints on this board I am reinventing the wheel to figure out what I am looking at.  I am thinking that there is a simple part that is failing (maybe diode or capacitor) which would be a $2 fix vs anything serious likethe main chip. This is just my opinion based on how it is randomly acting and my experience fixing other instruments.  Any suggestions on any documentation for this?  Have not been able to get in touch with the right person at topcon as they just refer me to a dealer nertwork.  Thanks

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  • Government Professional

    Look for the emitting diode, dust inside the lens or mechanic parts,and be ultracareful with trims or any variable resistor you find near the emitting diode, you will need some calibration after the repairment remember that if you change frequencies the instrument will tell wrong distances.

    First I would try to clean the lens, sensors and mechanics.

    Good luck

    • Thanks.  I will try cleaning it.  Wish there were some prints on this but so far I have no documentation on the electronics so it is kind of a guess as to what is going on here.

  • It is a myth that certain brands are better than others. I had a Nikon DTM 720 where the motor failed and while mine was getting fixed several people with leica gear were having similar problems ...so beware the brand-loyals who probably stick to them as its the devil they know and refuse to change!!

    • It is no myth. I have tested several different instruments including the Topcons, Trimbles, Sokkias and Leicas. Granted, I have not tried the Nikons but the cheaper brands are nowhere near Leica. I tested a Trimble S8 1" instrument on a galvanised steel girder about 30 metres away and was getting sd's of 4mm.

      The Leicas are way, way better than the others, and if reflector less work was critical to me I would buy nothing else. I would even buy a second hand 1100 before any of the newer others for reflectorless.
      • Hi Wayne, yes I agree with you there for accuracy and precision it's hard to get close to the top of the line Leicas in fact if I was doing anything serious I'd definitely go that way. I too have had issues with S6 Trimbles. I tried and tried to get consistent results on a baseline and just couldn't..It was baffling tried different reflectors PC's and all that and got nowhere. All the Trimble dealers would say was that it was working within the specifications..Well I ask you ..those sort of variations are random and not tolerable in my book. In fact I was so dismayed at their performance that I was almost scared off for life. To this day nobody has explained to me why we had a problem. On the Leica we got consistent result everytime ..Free Station setups to within 1-2mm, on an accurate network, whereas the Trimble gave us always 3-6mm and no pattern. On the test base we our results were so inconsistent the Government tests done refused to provide a certificate for the instrument, or if they did they stated there were some serious issues going on

        We performed the same sort of measurements with an older TCA1103 and got great results everytime..

        When I was mentioning other brands I was merely saying it was horses for courses and for basic surveys your options are far wider IMO. The top of the line Leicas are of much better quality than the lower end.

  • Tim parts are getting rare and are not cheap. The most likely thing to go wrong it this very tiny stepper motor which controls the measurement operation.. They are fiddly to get to and they cannot be repaired..$1600 is probably a fair assessment of what you have there!!

    • I will check this when I take it apart.  Thanks.  Any info on what kind of stepper motor it is?  Is it a unipolar, bipolar or multi phase stepper?  Wish I had some prints on this thing.  Maybe I can tell when it is apart.

  • Yep...buy a Leica if you want GOOD reflectorless. I am not joking around, the others are rubbish. 

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