My topcon marksmen rl-60b lazer that I bought in 2001 has been unable to activate and project a signal,with the out-of-level light blinking,no matter how perfect I get the bubble in the circle.is this just...
taken from Pauldos Personal Laser Blog,
The Topcon RL-50B and RL-60B leveling lasers use a fairly unique compensator arrangement. Most leveling lasers use a suspended compensator arrangement, with a lens or mirror on the pendulum. The pendulum is usually metallic, and inside another metallic barrel, so that an electrical connection between the pendulum and outer barrel indicates to the electronics that the compensator is 'out of range'. The RL-50B/60B has a fluid compensator system where the laser beam is reflected off an interface between the fluid and a window, with the level of the fluid influencing the reflection angle of the laser beam. Because there is no electrical aspect to the compensator, an optical system is used to detect when the compensator is 'out of range'. In the output structure of the laser, a glass window at forty-five degrees is used to reflect a small portion of the beam to a photo detector. When the laser is level, the small portion of laser beam strikes the photo detector.
A common fault with these lasers is to constantly indicate 'out of level'. This occurs when there is insufficient beam intensity on the photo detector. The standard solution for this fault is to clean the 45 degree window. Sometimes, this does not bring the laser back to life. I have stripped down a couple of these lasers to try and figure out what is going on.
At first, I thought that maybe the laser diode could be down on power, reducing the available beam, but I quickly discounted that, because the laser diode output is feedback controlled, so the output power is stable up until the point of complete failure. One of the units I disassembled had cracks in the compensator housing, and the fluid level was low. I don't know whether the fluid leaked or evaporated, but in either case, there was no way the compensator could be repaired. In another unit, I noticed that the fluid was discoloured. Since I don't know what the composition of the fluid is, I don't know what could cause it to discolor. Perhaps extremes of heat or cold may damage the fluid. If the fluid is discolored, that may reduce the available laser power at the output. The question is, can we compensate for this? (pun not intended)
I decided to reverse-engineer the photo diode circuit, and see if there was any way to improve it. There is. The photo detector amplifier is a standard op-amp inverting amplifier. The feedback resistor, surface mount R23, is 470K. I changed this resistor to 680K to increase the gain of the amplifier, and bingo! the laser works like a real one again. Extensive testing in the workshop and in the field shows that the laser functions as originally designed in all ways. I have done this modification to over fifty of these lasers now, and the modification extends the life of the laser anywhere from a few months to a few years, with the average about one and a half to two years. Customers are always happy to not have to buy a new laser for another year or so, so this modification is always embraced when offered. I have never figured out what is going on with the fluid, but since I have a solution (again, pun not intended), I don't care.
cleaning instructions :
Remove the housing. Remove the battery holder. Loosen two small silver grub screws on the turret. Lift turret off. Clean slant window with acetone and a cotton bud. Avoid smearing the glue in the corners over the window. Flatten and curve a cotton bud to clean the inside of the slant window. Clean the folding mirror under the slant window. Replace the turret. Turret has a small amount of play, so align it for best operation before tightening grub screws. Re-fit battery holder and housing. All done!
Sep 18, 2011 |
Topcon Rlh3c Rotating Laser Level W...