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Digicomp II troubleshooting

edited December 2012 in General

I just got my new Digicomp II, serial# 0005, and wondered if you had additional troubleshooting tips than are in the manual?

- The ball sometimes jams coming out of the ball release. It seems like maybe the connecting rod needs to be a touch longer? How would I best adjust it? Or should I round off the corner on the underside of the input guide, where it seems to be catching? I don't want to be hasty with the sandpaper, because I can't undo it.

- The balls don't seem heavy enough to push down the start switch. Maybe that's related to problem 1, but it seems to happen even if there aren't any balls in the input guide.

- The ball seems to be getting stuck on flip-flops, like they aren't quite heavy enough to move them, or there's too much friction.

Yes, I'm using the "tall" positon, and the table is level. Thinking about putting a couple books under it to jack it up even higher.

Maybe I just need to let it warm up and adjust to the humidity in my house? It just came off the UPS truck, and it's 15ºF out.


  • Sorry to hear about the trouble.  The ball release wire is carefully tuned in length, so it probably is a good idea to let it warm up, adjust to room temperature, and so forth before worrying about anything.   If the balls and brass pins are cold and condensing water, that could easily cause additional friction, so give it a bit of time. 

    Every single one of these First Edition kits is tested on (quite seriously) hundreds of balls worth of operations, to make sure that the ball release mechanism was "just so," that every flip flop was working smoothly and that it was 100% reliable on every single function before it ships.  It probably will not need much (if any) adjustment to get it to work well.  Once it is warm, you may want to "exercise" the start lever and flip flops, gently, to make sure that nothing is catching anywhere.  

  • Putting 2" of books under the legs helped a lot. I put 11 balls in the hopper, set it to "count", and walked away- came back and the accumulator read "0001011". I also noticed the last ball gets stuck on the Start lever- apparently the weight of the ball in the ball release is needed to make it turn the whole way.

    My wife was mystified by it, and finally got it when I said it was a "gravity powered computer".
  • It should definitely still activate the start lever, even when the input guide is empty; that's one of the critical tests that we repeat dozens of times.   Let it sit for an hour or two and try again. :)
  • It's working a lot better now, even without the books under the legs. The last ball still gets stuck on the start lever, but that's not really fatal. Multiply, Count, Clear, and Complement all work fine, although T4 sometimes sticks when resetting, a brief tap gets it going again.

    Maybe it's the uber-low humidity? I have to keep my house around 20% when it gets cold here in Minnesota, otherwise I get too much condensation on the windows.
  • Good; that sounds a lot better.   I'd imagine that more humidity would be a bigger issue, as the wood pieces may not slide so easily.

    For T4, do you find that it "clicks" when you slide it from one side to the other?  If so, you may find it helpful to very slightly loosen the four wingnuts, turn the Digi-Comp on its RIGHT side, and tighten them again.  If it does not "click," but is just a little "slow," do not loosen the wingnuts. Put one finger on the pivot pin head to hold it in place, and turn the switch back and forth a few dozen times to loosen it up.

    For the start lever, put your finger on the spot where the connecting rod meets the START lever, and apply gentle pressure at that location while gently moving the lever through its full range of motion, several dozen times.  We've found this to help loosen things up.
  • That helped with T4. I could feel a "scratchy" feeling, a wood on wood texture. After pushing on it and turning it back and forth a bunch of times, it smoothed out, and then worked fine. Which is good- the complement operation is my favorite part.

    However, I don't feel any scratchiness on the Start lever, with various amounts of pressure on the rod connection. I hear a little bit of a squeak if I push it at the right angle, kinda like wood on brass. I'm tempted to add a touch of weight to the arm, but I can't think of a nice way of temporarily attaching it.

    I've taken a couple video clips, I don't know if you'll be able to tell anything from it:

    They're vertical aspect- click "view full screen" if you browser letter-boxes them.

    Like I said, I don't think this is a fatal flaw, since the operation is "done" at this point. I only bring it up because you seem concerned, and of course, I'm a nerd, and need things to work perfect.
  • OK, I figured out a way to temporarily attach a little weight to the arm, and I'm right, it does make it work. I put a 1" #6 machine screw and T-nut on it, like this:

    Do you suppose it's because of the humidity? There's a lot more wood on the left side of the arm, so if it's really dry then it's going to weigh less. I wouldn't think that much less, though.
  • The test that we use-- before it ships --is that you need to be able to place a ball, at zero speed, right above where it says "MAN," and it should work *every time* for dozens of balls in a row.  It's a pretty rigorous test.

    Now, what we have found is that when our Digi-Comps have been sitting still for a few days, they tend to stiffen up a bit, and we do need to "exercise" the start lever for a little while in order for this part to work reliably.  The stiffening is because the wood relaxes over time and possibly with humidity changes.  The likely sources of friction are as follows: 
    1.  The hole through the center of the start lever vs. the brass pin
    2.  The start wire through the hole in the start lever
    3.  The start wire through the hole in the ball release.

    I'd suggest applying a little bit of force as you wiggle these connections separately, to loosen them up.  For example, turn the start lever a few times, while pressing with modest force towards the four sides of the board.  And as I suggested above, firmly hold the points where the wire meets the start lever and ball release, and apply some pressure to loosen up those holes.
  • The added weight is slightly inelegant, but a fine solution. :)  You may be able to add a little extra weight *under* the lever to make it a little less obvious. 

    The danger of too much weight on that side is that it will not return up when there are a lot of balls in the input guide. 
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