Talyvel1 electronic repair questions
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  1. #1
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    Default Talyvel1 electronic repair questions

    I have an older Talyvel 1, and having indicator issues, fluttering needle, etc. Powering it is not the problem. I decided to replace the capacitors, but having to find exact replacements are almost impossible and most unobtainium. Has anybody successfully repaired the electronics on one of these older units? They look to be rather simple...but.

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    Well since I got such great feedback on this, I though I would post an update. I replaced all electrolytic capacitors with similar values. It seems to be more consistent, but really didn't fix much. One thing I would like to make clear to potential buyers ( EBAY, etc.) of these vintage units(Talyvel1&2 ? ) , If it doesn't work perfectly now...IT IS WORTHLESS!!!. DO NOT PAY BIG BUCKS IF YOU CAN'T VERIFY THAT IT WORKS PERFECTLY!!! So many of the vintage components (germanium transistors) are almost impossible to replace. I am working to make a replacement board, but it is alot of work, and I just hate to have a worthless piece of crap in my collection.

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    that's an old lvdt conditioning board. replacing the components could be difficult if you dont hanve the schematic,and even you successfully repaired it, it's not a very good LVDT amplifier(aged over 60 years), i suggest you just keep the sensor-head and try to connect the sensor to some other newer conditioning model, like digital ones. i tried many sensors with solartron ACS SI100(orSI200/SI400) it has LCD screen and could RE-scale the readings, witch is easy to calibrate the new system,and it has standard modbus function , easy to log the measurement data, hope that could help

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    Thanks for the reply. I still haven't given up on fixing this one. I have a "top guy" going to look at it, but that hasn't happened yet.

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    Have you contacted Taylor Hobson?

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    Oh yes, a couple of times and my friend who has a "downed "one as well, same response. They cheerfully sent the users manual which is widely available, but when asked for a workshop manual and or schematics...crickets.

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    Quote Originally Posted by daryl bane View Post
    Oh yes, a couple of times and my friend who has a "downed "one as well, same response. They cheerfully sent the users manual which is widely available, but when asked for a workshop manual and or schematics...crickets.

    If you could just find a mole in the organization or a retired engineer.

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    I get the impression that Taylor-Hobson might have an "arrangement" with a firm over there (UK) that specializes in retro fitting these older units to modern electronics. Very expensive, $5K last time I looked, and I am sure is a very small market.

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    "Needle flutter" in the Talyvels can be due to insufficient damping of the pendulum. This is easy to adjust and I thought that I would document the procedure here.

    The damping comes from a small drop of high-viscosity silicone oil (50,000 to 100,000 cSt viscosity, according to the patent). This oil drop is held by surface tension between the bottom of the pendulum (a flat surface) and the top of a domed cylinder which is threaded for adjustment. If there is not enough damping, you move the domed surface closer to the bottom of the pendulum. If that doesn't work, replace the silicone oil drop. A small tube of 100,000 cSt viscosity silicone oil can be found online at low cost -- I think it is used in the differentials of radio-controlled model cars. A Google search for "Losi Silicone Differential Oil Fluid 100,000 cSt" should find this.

    On the new-style Talyvel heads, it's easy to access the adjustment screw from underneath. On the original Talyvel heads it is also possible, and that is what I am documenting below.

    (1) Tighten the two locking micrometer knobs and remove the bottom cover


    (2) Use a sharpie to mark the orientation of the leaf spring


    (3) Loosen BUT DO NOT REMOVE the two retaining screws. Don't touch the central screw


    (4) Remove one side


    (5) Lift straight up to remove the other side


    (6) Fully loosen the two locking micrometer screws. From here on, take extra care, as the pendulum is free to swing. It goes without saying (but now I will say it) that you should do this work seated in a clean, well lit area, with an uncluttered work surface and your tools at hand.


    (7) Remove the two screws/washers that you loosened in step 3


    (8) Support the bottom of the frame with your finger, as it wants to spring to the left, and remove the bottom leaf spring and post assembly with your other hand. Don't touch the pendulum! Since there is not much space for your fingers, some needle nose pliers are helpful to remove the leaf-spring and post assembly. Grab the central nut but don't turn it or loosen the post.


    (9) Release your finger pressure to let the support frame assembly rotate to the left.


    (10) Tighten the two top micrometer screws to swing the frame and pendulum out to the side


    (11) You now have access to the adjuster for the damping, under the small spring finger. It has three holes spaced at 120 degrees that you can rotate the adjuster with.


    (12) I use sharp-tipped tweezers in the two holes. Rotate the domed screw about 1/8 of a turn. Tightening it (clockwise rotation) reduces the gap and increases the damping.


    (13) To reassemble, loosen the micrometer screws to rotate the frame back, then follow the same steps in reverse. To get the bottom post to fit into the slot, you will have to gently push the bottom of the frame back into the middle of the case. Be sure to push on the frame and not on the pendulum.


    If you tighten the domed screw too much, you will block the swinging of the pendulum. It's not a problem, just back off the screw enough that it no longer interferes. If you can't get enough damping, remove the screw, clean off the old silicone oil, and add a new drop.

    You can test the damping without reassembling fully, so once you have done it a couple of times, the entire process takes ten or fifteen minutes. You tweak the position of the damping screw, test it, and tweak some more until it's good. Each cycle takes a couple of minutes. The ideal position is "critically damped" which means that the needle settles in to the final value, without overshooting, but is on the verge of overshooting.
    Last edited by ballen; 09-08-2021 at 05:36 PM.

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    Excellent. I might add at least on mine,( older unit) that the domed screw that rests on the silicone blob is made of clear plastic. If you remove the little copper? spring holder and with a (torch) flashlight , you can screw in the domed screw, see when it touches the silicone blob and then adjust accordingly.

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    One other point. On the bottom plate that has that central post bolt in the middle. I have deduced (maybe erroneously) that its only purpose is when you unscrew the micrometer dials all the way and the frame of the pendulum unit is resting on the isolastic pads, this central post contacts the pendulum unit through the frame and relieves the tension on the pendulum wires so that the unit can be transported or shipped without damage to the wires. I believe it should be adjusted so it barely pushes the pendulum unit just enough to relieve the tension on the wires.

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    Quote Originally Posted by daryl bane View Post
    On the bottom plate that has that central post bolt in the middle.
    This central post has two purposes.

    First, it controls the lateral position of the pendulum support frame. The springs of the adjuster plate at the top tend to swing the frame out to one side. The central post rides in a slot in the bottom of the support frame, and prevent this sideways swinging out motion.

    Second, as you say, it is part of the locking mechanism. When you tighten the two micrometer screws on the top, this pushes the support frame and pendulum downwards. The post passes through the slot in the support frame (described just above) and normally rests below the pendulum. But in the last turn or two of the micrometer screws, the bottom of the pendulum is blocked from downwards motion by this post. As the micrometer screws are tightened, it pushes the bottom of the pendulum firmly onto the post, until the pendulum is pushed upwards, against the upper stops (adjustable screws) of the frame. This relieves the pressure on the support wires and blocks any movement of the pendulum.

    I don't know how much this post should impinge, so have been careful not to touch or turn the adjustor for this central post. If I had to adjust it, I would ensure that (when the micrometer screws are fully tightened) the post holds the pendulum firmly against the upper stops. Note that the post is attached to a leaf spring assembly that allows some small motion.
    Last edited by ballen; 09-11-2021 at 02:15 AM.

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    You're right. I forgot that the springs do push the pendulum unit and that post keeps it centered.

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    Update. I was able to procure a working Meter unit from a forum member here (ballen,,thanks again ). I think he felt sorry for me . And I now have a working unit. The good news is that the level reader head works correctly. I was scared that it might have been faulty, and that would be very bad news. I am amazed at how sensitive these units are. I had it sitting on my surface plate which is on a substantial stand, and I could detect movement as I walked around. There was some needle flutter that turned out to be my heartbeat as I had my arm resting on the surface plate. I will now start to trace out the old board at my leisure and will post it here, but it won't be real soon.

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    News flash: I've gotten hold of some more Talyvel literature, and can now identify the exact Silicone fluid being used for damping. It is Dow Corning DC200/200,000 centiStokes (cSt), Rank Taylor Hobson code 9103/027922.

    The closest that I could find on-line is Down Corning XIAMETER™ PMX-200 Silicone Fluid, which is available in different viscosities: https://www.dow.com/documents/en-us/...0-si-fluid.pdf

    The difference between 100,000 and 200,000 cSt is relatively minor, so either should work with appropriate domed-screw adjustments.

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    I just want to say that THIS kind of information exchange is the kind of thing that is infinitely valuable on this site. Priceless, as it were.

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