woelen
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Manual or operating instructions of H80
I obtained an old H80 analytical balance. It is made by Mettler-Toledo, I think it is equipment from the 1970's or maybe start of the 1980's.
The device does not work properly. It has a knob, for selecting grams, tens of grams and fine adjust. First, the knobs for tens of grams and then
grams must be adjusted, so that no + or - is displayed, but some fraction of a gram at 2 digit accuracy. When this is done, then the fine adjust can
be used to obtain a result to 0.1 mg accuracy.
Unfortunately, my balance shows a fraction of a gram at multiple selected weights. E.g. if I take a 25 gram object, then I obtain a fraction of a gram
for e.g. 22, 23, 24, 25, 26, 27 and 28 gram.
If anyone of you has a manual, or a diagram/scheme of the device, then I would really appreciate if this could be scanned and uploaded. Unfortunately,
Mettler-Toledo has no online documentation for the H80 balance. Without the documentation, I'm afraid that I only destroy the device further, if I
open up the case, with all its VERY delicate mechanics.
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Blind Angel
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I got a H10 which goes up to 0.1mg too, there is no problem opening the case, i need to do it often. These balance are atomic-proof it's crazy (using
a 1mg taring weight i get ±0.3mg of difference, for my use i consider it still calibrated). Open the case and check if all the ring are in their
respected position. Also with my model you must first run the balance in to ½-mode where you weight the gross mass, after you go into 1-mode where
you adjust the fine knob. Care to post a picture?
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S.C. Wack
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His has a very different mechanism than yours. I'd like to see a picture of the works. I don't quite understand what woelen posted as a problem, and I
would think that woelen knows enough to level it with the bubble on top, and note anything misaligned or locked down.
The last digit accuracy of old scales like these is a little misleading due to the adjustment knob (the one on the right side of Mettler and Sartorius
balances) manipulation and/or scale being less sensitive than the balance; so it's no surprise that it is difficult to get perfectly exact
measurements with exact weights. A 2 number difference on the last number is on par.
[Edited on 10-11-2006 by S.C. Wack]
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woelen
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I have taken the risk to open up the device and I already have it working now. It is amazingly accurate, I can measure weights well within 0.3 mg
accuracy  
! It took me almost 5 hours to fix it, but I succeeded .
The balance is working by using two sets of rods:
1.0000, 2.0000, 4.0000, 8.0000 grams
10.0000, 20.0000, 40.0000, 80.0000 grams
The balance itself only has a range of weighing 1 gram, starting at 159.0000 gram and ending at 160.0000 gram. With no load, the balance is at
equilibrium when 159.0000 grams are in it, then it shows 0.0000 gram. This is achieved by putting all rods in the balance. With a mechanical
construction, rods can be taken out of the balance. When I put a weight of less than 1 gram in the scale, then the device shows the weight. If I put a
weight of more than 1 gram in the scale, then it shows ++. The trick now is that rods can be taken out of the balance by means of a very nice and
ingeneous piece of mechanics. If I e.g. put 5.2 grams in the balance, then it shows ++. But by turning a knob, I can take out 5 grams (by taking the
4 gram and 1 gram rod), and the scale shows 0.2 grams. The weight, taken out of the balance also is shown, and in this way, I know that I have 5.2
grams. If I take out too much weight from the balance (e.g. 6 grams, 4 gram rod and 2 gram rod), then it show --. So, I have to turn on the knobs
(taking out rods), such that it does not show ++ nor show --. It should show a number between 0.00 and 0.99. The number in front of the decimal digit
is determined by the rods.
Finally, when the balance shows the two digits, there is a final fine-adjustment, allowing me to select the last two digits. This is done by turning a
third knob, which excerts a variable pressure on the scale, which is VERY subtle. This can be used to finally measure the last 0.0000 to 0.0099 grams.
Readout is done by means of a bar, which must be positioned exactly over another bar. The sensitivity of the positioning of the bar is such, that
measurements at 0.0003 gram accuracy are no problem at all. Measuring at 0.0001 gram accuracy is somewhat hard, however and a little uncertain. So, I
consider it to be a scale, which can tell me the weight in a 0.0003 wide interval, e.g. 5.2000 ... 5.2003 grams.
Here follow some pictures:
The device itself:
And here some detail pictures of the mechanism with the rods:
The nice thing is that the device is purely mechanical. It does not contain any electronics, except a light bulb for backlighting the display for the
digits and the adjustment bar. When this device is used carefully, then it will remain working for a life time.
[Edited on 10-11-06 by woelen]
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Blind Angel
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Man I love those balance, pure genius! Having more money, I'd collect them. I had a friend, whose kinda well her.. stupid, bought a H20, then he saw
that it wasn't working and instead of trying to twink with it, he used the ring inside to smoke hash oil...
Oh so nice to see such a perfect mechanism, i should post picture of mine too 
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