Repairing Heindenhain VRZ 753B + LS803 scales - Page 5
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  1. #81
    Join Date
    Sep 2011
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    Hi Bob,

    Quote Originally Posted by HBOB View Post
    Of interest to me is the reference to using a IR type LED as a replacement for the scales light bulb. Wondering if you tried the so called near or the far IR type?
    These Heidenhain scales use silicon solar cells. Those have a spectral response which extends up to wavelengths a bit longer than one micron (1000 nm). Spectral Response | PVEducation . The near IR LEDs emit at wavelengths up to around 950nm, so those are a good match. The far IR LEDs emit at much longer wavelengths, where the silicon solar cell won't respond. So use near IR LEDs.

    And what were/are your thoughts on LEDs usage as a bulb replacement.
    I've replaced one burned out bulb with an IR LED and am happy with the result. So if I have any more bulbs burn out I will do the same.

    Would you consider sharing some more information .about the 11 micro amp to ? volt converter you made? Know that I would be interested in a schematic an how you calibrated it. Also think other readers in the present or the future would find that information very useful.
    OK, I will do this at some point in the future. Don't have the time to do it now.
    Last edited by ballen; 01-16-2019 at 02:11 AM.

  2. #82
    Join Date
    Dec 2002
    Benicia California USA
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    Bruce has had better luck than i have with the LED conversion....
    Spent some time and energy making carriers and mounting LED's on the reader heads for the rotary encoder on the universal table...

    Had some success getting the scale to read and output a reasonable shaped signal, but could never get enough output to be reliable.....
    Eventually i went back to the incandescent lamp to get the encoder to provide a reliable output.....

    Made new carrier to hold the LED....Original and new .................

    Output side of LED

    New carrier..............

    I have drawings for the carrier if you would like.....

    Cheers Ross

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  4. #83
    Join Date
    Mar 2017
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    Quote Originally Posted by jz79 View Post
    the old glue (most likely it is silicone) is still firmly stuck to the glass, my plan was to leave it there so it continues to work as the buffer for vibration and thermal expansion differences between the glass and the aluminum case

    anyway, it does seem to be some sort of a silicone, because the urethane dabs I placed on it cured and didn't adhere at all, could be easily picked off

    I ordered Dow DOWSIL 3145 link to product info pdf), from the description it looks to be the perfect stuff for this, pretty pricey, ~60eur for a small tube of 90ml, maybe some cheap sanitary silicone would also work, but I'm afraid of any unwanted additives those may contain, solvents or worse - acids etc, that might damage the deposited measuring stuff on the glass

    and as a backup I also ordered Loctite 770 primer, supposedly it lets CA glues to stick to silicone, but that will be the last resort, I'm afraid of the CA fogging up the glass scale, I could perhaps warm the glass up little bit and cool the aluminum case somewhat for any possible fumes to settle on the case, but that will be the last option
    small update, the Dowsil 3145 silicone glue worked really well, the bond to the old silicone glue on the glass scale was as strong as the parent material, and it adhered to the anodized aluminum case very well as well, so in case anyone has to glue the glass back into the case - this is the right glue to use

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