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Old_school
Tinkerer
Username: Old_school
Post Number: 8
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 25, 2011 - 04:54 am: | 
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Just a few comments on these old meters:
1) This stuff is extremely toxic, so do not put your fingers in your mouth after handeling these cell. Latex gloves & a mask would be a good idea if you create any dust. Clean your bench after you work on one.
2) The old timers said that the cells would fail due to shorting out. They said to just isolate the damaged section from the good & recalibrate. I never tried this out.
3) I found that if you pull the cell on like the WESTON Master V out & took an ink eraser to the back contact surface area & reassembled they worked nice.
4) Anytime you have to work on a galvanometer style movement, clean the area of any stray iron particles to prevent the attraction to the magnet in the movement. Maybe do a sweep of the bench aera with a magnet before you start to service them. If you pick up a stray iron particle, a pin or needle can be used to fish it out. Just touch the pin or needle point to the particle & you should be abel to attract & have it stick to the pin point. A needle stuck in a piece of peg wood so the point is out makes an excellent handle a spot of epoxy to hold it in couldn't hurt.
Maybe later I give a general comment on balancing a movement.
Once again this stuff is nasty, so be careful! If you see yellow optical glass, it may also be selenium.... |
Georgeboosh
Tinkerer
Username: Georgeboosh
Post Number: 19
Registered: 04-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, April 25, 2011 - 11:39 am: |
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Some useful information. Thank you. |
Waynemel
Tinkerer
Username: Waynemel
Post Number: 50
Registered: 08-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 26, 2011 - 06:47 pm: |
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Thanks for the info. I am trying to revive an old Gossen unit and could use some help.
I need to re-solder the fine coiled spring on the top of the unit, at the base of the needle. There are two of these coils, one on the top and one underneath. Do they both coil in the same direction? In other words, does one un-coil while the other coils tighter, or do they both work in the same direction at the same time? |
Old_school
Tinkerer
Username: Old_school
Post Number: 10
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 26, 2011 - 08:35 pm: |
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Just looked at a galvanometer in a battery tester & they are in oposite directions, looking direct on & through to the other side.
Use a low watt soldering iron. To keep the coil from moving on you very carefully wedge a V shaped piece of paper in between the magnet & the coil, a number 5 or 3 point tweezers works nice for the delicate work here. Usually, I take notes as to the direction the coil is going before attempting any work. Anyway, if the hairspring is in good shape & your going to reattach it, with your elbows on the corner of the bench for stability, proceed. The soldering iron may attract the hairspring so have a good firm grip on it & see how it goes. Try to get it so it is flat, level & concentric to match the other side. If all goes well, remove the paper wedgie & balance the pointer. ? Yes, move the adjustment so the pointer is not on its stop, free floating, check for position error. Up, down, left, & right, add a little bees wax if needed to balance or spot of paint a little at a time as it should not take much if all goes well. When balanced, return to the zero reference position & calibrate. I was only able to get one gal in a shop of about 60 to even attempt this so, be patient & take it slow. Some of the movements had three hairsprings, fun!
Ref: why not?
http://en.wikipedia.org/wiki/Galvanometer
If you have a broken taught band, the material is platinum & we never repaired these, just replaced them @ $1000. a pop.
So if you have a broken taught band movement, before you pitch it, grab the taught band material off it first as it could come in handy. |
Old_school
Tinkerer
Username: Old_school
Post Number: 11
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 26, 2011 - 09:04 pm: |
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By the way, see my other notes on the Canon FTb as to movement handeling. Once you are happy with everything clean the stops & the pointer sides where they hit the stops with a clean solvent, a very light touch & light on the solvent so as to not remove any pointer paint or get the scale. Stainless steel tweezers, bronze or titanium are also nice as they are not attracted to the magnet. If the viewing window is glass, lightly fog it with your breath to discharge any static before reassembling. A solvent that would work good for this is One Dip a hairspring cleaning solvent for watch hairsprings, I think, @ a watch material or jewelers supply house.
42 & good luck! |
Hanskerensky
Tinkerer
Username: Hanskerensky
Post Number: 91
Registered: 05-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, April 26, 2011 - 11:44 pm: |
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Some very good tips Michael, thanks for sharing ! |
Ron_g
Tinkerer
Username: Ron_g
Post Number: 73
Registered: 07-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 27, 2011 - 01:46 am: |
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I have a meter coil that needs to be rewound.I am looking for a sewing machine motor that is not being used and will fabricate a jig to be able to do this if I ever get the time.
It has been put on hold for the time being as I can be much more productive doing other things.
I have pictures of a galvanometer that I repaired in motion with the needle swinging driven by a function generator to make sure that it will work properly after I reinstalled it in the camera.
It came from a Voightlander Vito CL.It works very well as compared to other meters in other cameras.Ron G |
Old_school
Tinkerer
Username: Old_school
Post Number: 12
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 27, 2011 - 05:43 am: |
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I ran across a machine for that some thirty years ago in an electronics store & did not realize it's value or potential at the time. Or maybe had a hunch, but no where to put it. Anyway, a late friend used a capacitor checker of some sort, a bump switch with a quick discharge, that would some how fuse the broken coil wires together with a good success rate. I never have tried it my self, so I can't give any specific details on how you would go about it. Just have this vision of a smoked coil & hairspring......! I did that once, & still can't believe I smoked it.
But, some people can't leave you alone to think clear & they want it done now. I am sure it was an expensive mistake & no one was happy. 400 cps at 115v makes things hum & you jump! |
Old_school
Tinkerer
Username: Old_school
Post Number: 14
Registered: 04-2011
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 27, 2011 - 04:49 pm: |
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Tools: I had to sew a button on my shorts & thought of you guys.
A nice assortment of hairspring tools can be made from sewing needles. Either epoxy a sewing needle point end into an orange stick or piece of plastic rod to make a handle or heat it up & stick it the plastic rod. Then grind open the loop end to make more of a U end. Now you have a nice assortment of hairspring tweaking tools. With the advent of diamond grinding tools, wheels, flat grinders, you can make an array of them. Make sure to remove any burs on the inside of the U or it can damage the spring when removing the tool. |
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