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Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 135
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 02, 2007 - 09:38 am: | 
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On quite a few cameras (mostly Ricohs: 35 L, 500G, GX!) I found the meter wiring ok, the circuit's interruption is in or at the coil.
Even after finding the broken wire on the coil's surface - the damage was always resulting from tiny bits of green corrosion, often where the super thin wire is soldered to the retracting hairsprings, most probably because it had been treated with acidic soldering material). I have never been able to resolder that sort of wire, even if it was long enough. Has anybody got any idea or method how to solder copper wire thinner than a hair (wattage of the soldering iron, headloupe, "third hand", etc). This time I do not want to surrender or lose the old Ricoh I am presently working at because it is in super condition otherwise. Weanwhile I have even found a suitable replacement cell for the dead selenium element, W. |
Dgillette4
Tinkerer
Username: Dgillette4
Post Number: 29
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 02, 2007 - 09:56 am: |
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A soldering pencil very lowwattage works but use it on the wire for a short time if possible, also there may be varnish on the wire, you have to remove it to solder, it's not practical to scrape it off , I have used the smallest drop of paint remover then wiped carefully, this is like brain surgery...If you are not near-sighted like me you will have to use a loupe and always lots of light. I have made a third hand out of a goose neck and alligator clip, to hold solder etc. Also once you got the varnish off you have to clean off the remover, I used alcohol. A cotton swab and a steady hand helps..good luck Don |
Ben_hutcherson
Tinkerer
Username: Ben_hutcherson
Post Number: 46
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 02, 2007 - 10:11 am: |
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To remove the varnish, lightly and gently rub the wire on a piece of fine-grit sandpaper. It should come off, although it may take a couple of strokes.
Also, although it may seem wise to use a lower wattage iron, there are times when a higher wattage one comes into its own for this type of work. A higher wattage iron will require you to apply heat for a shorter period of time, while a low wattage iron may take several(damaging) seconds to bring the surface up to a high enough temperature to solder. This is often the case with really low wattage irons in the 10-15 watt range. I'd probably use something in the neighborhood of 40 watts, while being quick and deliberate in your work, applying heat for no more than a second or two at a time.
Also, a thin diameter solder helps. One of my favorite solders for pretty much everything is Radio Shack part number 64-035. It's a very thin rosin-core(for electrical work) solder with about 3% silver. The 3% silver gives it a lot more strength than standard tin-lead solders. Also, it goes from solid to liquid very quickly, with no in-between plastic stage while it's cooling. This makes it very difficult to have a cold solder joint. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 137
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 02, 2007 - 10:34 am: |
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Ok, so I am definitely not alone. I usually use a 25 watts non automatic soldering iron (I also use it for radio repair without any problems), but it turned out to get too hot, the wire itself melted away as soon as I touched it! I once read camera repair sometimes is like surgery on a mouse, but you are right, Don, it is like brain surgery (on a mouse baby) actually, I will do my very best, get/make myself the right tools, thin solder wire and then follow your advice, Don and Ben. Thank you for those quick responses, W. |
Donnie_strickland
Tinkerer
Username: Donnie_strickland
Post Number: 19
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 02, 2007 - 01:36 pm: |
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Just a thought: for camera work, I like to use Radio Shack Low Heat Soldering Tape and a Cold Heat tool. I was skeptical of the Cold Heat at first but after I got one as a Christmas gift, I have used it quite a bit. It works extremely quickly and (the part I really like) with very little, highly localized heat. Plus there is no tinning of an iron to hassle with. I prefer the optional conical or beveled tips on mine.
The solder tape, as the name implies, takes little heat to melt and so works hand in hand with the Cold Heat. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 138
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 02, 2007 - 11:53 pm: |
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I need a new one anyway, and I am still searching, so why not try out new ideas? Thanks for your input, Donnie. |
Charlie
Tinkerer
Username: Charlie
Post Number: 66
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 03, 2007 - 05:06 am: |
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Because my hands are shaky I have been using conductive epoxy rather than solder for attaching wires to circuit boards. I don't know how well it will work in your application. Conductive epoxy is available in the kits used to repair gaps in rear window defroster grids and are available in auto parts stores. The cure time is several hours. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 264
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 03, 2007 - 07:02 pm: |
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It's very tough.... I've done it successfully once and screwed it up once. I wrap a piece of stripped copper bell wire around the soldering iron tip with an inch or so sticking out to form a new, smaller tip.
It worked once...... |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 265
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 03, 2007 - 07:05 pm: |
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I agree with the wattage argument from Ben: the trick is to get in, make the joint and get out fast. You need a bit of heat (and quick hands) to do that. Too little heat and you sit there bringing the whole part up to within a few degrees of the melt point before your joint sticks, and your chances of losing the other end increase dramatically.
The same goes for other forms of collateral damage in soldering: low wattage is a very poor substitute for speed. |
Donnie_strickland
Tinkerer
Username: Donnie_strickland
Post Number: 20
Registered: 09-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 03, 2007 - 07:26 pm: |
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That's where I like the Cold Heat: It gets up to temp almost instantly and so you don't get the heat spreading to where you don't need it.
I should mention that I have used it on many cameras but I have not tried it on spool wire. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 140
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 04, 2007 - 07:47 am: |
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My success rate is poor, I have tried that operation four times and in the only positive case I then screwed up one of the retracting springs: collateral damage, as you say, Rick.
The current problem faces me with two ends of wire with a gap of several millimeters between them that have to be bridged. Everything looks easy. In a newly bought Minolta repair manual I read that in some cases soldering temperatures must not exceed 280 degrees Centigrade (which is not much for getting the solder to melt!).
Yes, Charlie, I have also thought of that solution you mention, but compared to a defroster grid, this joint has to be of microscopic dimensions! I haven't decided what route to take, and I do not know if that is the only problem to be solved on the meter, because I have now clear evidence to believe that the meter has been partially apart earlier. |
Ben_hutcherson
Tinkerer
Username: Ben_hutcherson
Post Number: 48
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 04, 2007 - 08:37 am: |
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Something else about heating things up fast and efficiently: you absolutely need to have your tip clean and tinned.
Before you turn the iron on, dress the tip with a fine file or piece of sandpaper. Once it comes up to temperature, wipe it on a damp sponge and then apply a thin coating of solder, followed by another damp sponge wipe.
Repeat the damp sponge wipe on the tip before and after every single joint.
Keeping the tip spotlessly clean helps to ensure that you get the most efficient heat transfer possible, and thus, again get things hot as quickly as possible. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 144
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 12, 2007 - 03:25 am: |
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Have gone deeper into the matter, and what I see is very annoying, very.
Take, for example, that Fujica AX-5 from that remote corner of my workbench. Excellent shape from the outside, but only default exposure time. On removing the bottom plate I found both ends of one solenoid's wire (as thin as meter spool wire, of course!) covered with green corrosive gunk! The battery chamber is like new and miles away. The question now is: what, if not a leaking battery, has caused that corroding away of the wires? My suspicion is that Fujica (just like its former competitor Minolta), perhaps for making more short-term profit, did not only use el cheapo electrolytic condensers in their cameras, but also used acidic solder, so the wires could be soldered without having to scrape off the insulating lacquer first. If this is right it is just a matter of time before more (all?) those thin wire's joints will be affected by the acidic componets of the solder used. Can anyone confirm this hypothesis?
NB the Ricoh is still sitting there waiting to be repaired, the tools ordered for the repair are on their way, I hope, W. |
Charlie
Tinkerer
Username: Charlie
Post Number: 67
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 12, 2007 - 05:06 am: |
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Interesting discussion of fluxes here http://www.newton.dep.anl.gov/askasci/chem03/chem03278.htm |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 268
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 12, 2007 - 06:44 am: |
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I think the acid flux theory sounds doubtful. People have known about that problem forever, and people even vaguely knowledgeable in electronics would not use it. Surely anyone building something like the Fujica AX5 would be more than vaguely knowledgeable in electronics. Besides, it doesn't save a detectable amount of money.
I do not believe that the corrosion in battery wires is caused by battery leakage. It typically travels far up the wire, even in cameras where there is no sign of corrosion on the battery contact itself. I believe, rather, that it is galvanic corrosion caused by the constant electrical potential in the wire from the negative pole of the battery. In the case of th eFuji, it may be that a gap in the coating on that piece of thin wire allowed corrosion to begin at that location rather than closer to the battery where the electrical potential was only slightly higher.
This does not make the repair any easier, of course. I think if cameras had been designed with a positive rather than a negative potential on the wiring, we might see less of this problem. Perhaps someone understands why cameras all seem to have "positive ground" electrical systems.....
of course, having said all that, i could be totally full of it too.... |
Ben_hutcherson
Tinkerer
Username: Ben_hutcherson
Post Number: 50
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 12, 2007 - 07:00 am: |
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Rick's galvanic corrosion theory sounds plausible, at least in my experience.
At the moment, I'm getting ready to rebuild my third high-power Ni-Cd pack for the Canon F-1.
Every single one I've rebuilt so far has had the cells covered by a nasty looking whitish corrosion. The original cell packs were totally spot welded together, with no solder except where lead wires are attached.
On my first pack, one of the traces on the circuit board had corroded to the point where it was impeding electrical contact. Once the corrosion was removed, and the cells replaced, the pack worked great. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 145
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 12, 2007 - 09:13 am: |
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On second thoughts, Rick, you are probably right, as the corrosion in this case did not start exactly at the soldering joint, but several millimeters along the wire.
The current problem now is to find out which end is which and where they go.
But soldering has become easier now: no scraping off of varnish, it only harms the delicate wire; the 12V 8Watts soldering needle (was in the mail today!) is exactly what I have been looking for: careful tinning of the ends (2 secs. approx., heat taking away the lacquer coating on doing so, contacting the two ends to be soldered together for half a sec., and that is it! Will try it on the Ricoh's meter next week after some more tests, W. |
Dgillette4
Tinkerer
Username: Dgillette4
Post Number: 36
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 12, 2007 - 09:42 am: |
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Another thing I have done to half the wattage of the soldering iron is to wire a 1 amp diode in series with the power cord on one side. Also good for smt electronics. Don |
John_shriver
Tinkerer
Username: John_shriver
Post Number: 13
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, May 14, 2007 - 06:50 pm: |
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I think some of the old wires from battery compartments had polyvinyl chloride insulation, which breaks down to form hydrochloric acid. I think that's what ate all the black wire in my Topcon RE200.
As for soldering, I'd start with a thermostatic iron with a low temperature setting, like 500 Fahrenheit. Also a eutectic 63/37 solder.
Stripping thin magnet wire, yeah paint stripper is pretty good. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 151
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 15, 2007 - 06:16 am: |
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Without mentioning the chemically correct names I once came up with the idea of a chemical reaction as a sound reason for "black wire corrosion", named so because this is the only wire being exclusively eaten up by it. And was promptly corrected by someone saying that the matter was not a chemical reaction. Now I am still sure it is, thank you John for your input. Maybe the whole thing is intensified or accelerated by electricity, W. |
Jonasc
Tinkerer
Username: Jonasc
Post Number: 2
Registered: 05-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 15, 2007 - 04:17 pm: |
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I am new to the repair of classic cameras and have never done any work with light meter coils but in my job as an electronic technician I have had to solder and repair countless coils. I use a Pace MBT solder/desolder station which is temperature controlled. I use the lowest temp that you can get the solder to melt and flow reliably. Make sure both parts to be joined are tinned, coated with solder, and that the connection between them in sound mechanically. Also use a good grade of non-acid based flux. And finally as everyone else has said leave the heat on just long enough to get the solder to melt and flow and for the joint to be strong. |
Charlie
Tinkerer
Username: Charlie
Post Number: 69
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 15, 2007 - 04:56 pm: |
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Maybe I'm not up on recent (since 1950) electronic assembly but I thought most coil wires were insulated with some form of varnish or enamel. |
Glenn
Tinkerer
Username: Glenn
Post Number: 150
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 15, 2007 - 07:37 pm: |
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The term 'black wire corrosion' is somewhat confusing. It does not originate from the observation that the conductor with the black insulation, is the one that degrades. 'Black corrosion' refers to the actual colour the copper or tinned copper conductors become, when this condition first manifests itself.
Initially this condition is not a chemical reaction, it is as Rick Oleson rightly observed a galvanic reaction. However as the condition progresses, depending on the actual chemical composition of the insulation, a chemical reaction can cause a further breakdown of the insulation. This can lead to the formation of various 'nasties' as the insulation continues to degrade.
In the 1970s/80s I was involved in the investigation of degrading cable insulation on the UK rail signalling system. These cables were manufactured to a specific British Rail specification and consisted of tinned copper conductors, surrounded by a layer of natural rubber insulation which was itself sheathed in nitrile rubber.
The problem actually surfaced when there was a network wide replacement of relays and lamp-holders. Technicians found that as they separated the bundles of cables and removed the terminations, the actual conductors were black. However a far more worrying feature was that the inner natural rubber layer was turning to a sticky liquid mass. Left undisturbed the cabling presented no problems, but the separation and movement during relay replacement would cause the nitrile layer to split.
After much detailed analysis and eliminating incorrect manufacturing procedures, contaminated insulation mixes etc, it was proved to be directly attributable to the constantly applied electrical potential in the DC circuits.
The problem was only solved by an expensive cable upgrade, not originally thought necessary in the original modernisation program. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 273
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 15, 2007 - 08:33 pm: |
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That's a very interesting account, Glenn. Fascinating how often you can find parallels of one sort or another between different fields of activity. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 152
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, May 16, 2007 - 12:28 am: |
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... which leads us to a kind of new topic connected to the initial one. Yes, Charlie, you are right as far as the original question is concerned.
I have been restoring antique radio receivers for quite some time now and I am using home-made audio equipment without having met any sort of "galvanic" corrosion so far. But in cameras one can find a special sort of degrading wiring, sometimes resulting from the multi-cause influence of seawater, leaking batteries, brown gravy, decomposing insulation or/and other harmful or corrosive liquids. The cure for this mess is putting in new wires, whatever may have caused havoc. |
Ethostech
Tinkerer
Username: Ethostech
Post Number: 67
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, May 17, 2007 - 05:14 am: |
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On the subjectof what is known as "black wire corrosion" I have started a new thread here ' Black Wire Corrosion". |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 154
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 02, 2007 - 01:42 pm: |
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Charlie, in your first post in this thread you mention conductive epoxy, and as soldering turned out to be impossible in any way (I tried three different soldering gadgets, but inside light meters everything is so small and vulnerable!) I did what you suggested, the gap between the coil wire's ends was just a few millimetres. Although it was not so easy to apply the epoxy to bridge the gap it worked fine, the light meter, like the whole camera, is ok again, thanks a lot, W. |
