| Author | Message | ||
     Ethostech Tinkerer Username: Ethostech Post Number: 68 Registered: 07-2006 Rating: N/A |
I have started this new thread because there have been of late many and varied postings (and responses to postings) which have alluded to "Black Wire Corrosion" within camera circuitry. As one poster pointed out - this doesn't refer to corrosion of a negative wire but rather to the conversion of multi-strand copper cores into non-conductive black powder - irrespective of polarity. During the timeframe of useage and creeping corrosion the resistance of the formerly good zero ohms gets higher and higher until eventually one ends up with an open circuit. So the camera (or whatever the appliance) becomes less and less operationally efficient until one day - the open-circuit factor kicks in and everything fails. What causes black wire corrosion (BWC) ? It is known that the chemistry of rechargeable cells such as ni-cads, is a serious consideration - but it is not the complete answer because non-rechargeable mercury cells are also associated with BWC. If anybody ever finds a proper technical answer - then such companies as the Japanese Futaba Corporation, the German Multiplex Company and a dozen other manufacturer's of radio-control equipment for model aircraft etc., would surely like to know - because they have been trying to sleutht he issue for the past 50 years .. without success. The straight answer as to what causes BWC - is that nobody knows for certain. However - part of the inspection pocedure which all model aicraft clubs and their governing national Associations require in the "certification" of RC transmitters and receivers - is that the wire leads from the battery-cell pack to the first soldered connection on a tag or pcb, yield a zero ohms measurement. Otherwise those wires must be replaced. If a camera stops working due to BWC it is really nobody's neck. If however a $15000 model helicopter goes berserk and drops out of the sky at a model flyng field the results can be lethal. ( Never mind the expense noise which such a bag of whirling nuts and bolts makes when it hits the ground) I spent 30 years flying RC aircraft and I can tell you that the number one fear is BWC - and it is vital that the above-mentioned checks are carried out at least annually. I also have some 400 cameras in my "Collection" - every one of which came to me in various stages of "non-working" - and which cameras have been restored to mint or near mint condition and 100% functionalty. I have never yet encountered a zero ohms (or anything close) resistance on the power supply wires in 20 to 40 year old classic cameras which are of nic-cad or mercery-cell technology. If I knew the technical answers I would be avery wealthy man overnight. All we know is that it happens and the service solution is to replace wires from the battery compartment terminals to the first tag or pcb solder point. If (as in some cameras and RC equipment) there happens to be a "push-connector" in series with such wires - then those connectors will also be corroded and must be scrapped and replaced with either a new connector or by a sound soldered joint. There has been some speculation on this forum that the chemistry of the wire insulation might be a contributing cause - but such has been investigated ad nauseam by RC manufacturers and ruled out. Similarly has galvanic corrosion been ruled out. There were also some speculations that such manufacturers as Fuji, Canon, et al .. may have used inappropriate fluxes. (Flux is required to tin the stainless steel tags of mercury-cell battery compartments). It is more than axiomatic that such highly experienced manufacturers do not make such fundamental mistakes - but in any event the fluxes element was eliminated as a BWC trigger ... some 30 years ago. The short summary is that if a camera tinkerer finds erratic metering readings with cameras of ni-cad or mercury cell technology - the first check should be to disconnect the primary battery-power lead/s at whatever the business end pcb or tag - and check such lead back to the battery compartment tags - for a zero ohms reading. If higher than 0.1 of an ohm .. then renew the wire. Don't worry about WHY the BWC .. because the chances are you will never know the answer. Hope this helps. |