Products > Test Equipment
An ugly but working HP6060B Electronic Load
AMR Labs:
--- Quote from: Swake on January 23, 2023, 08:25:59 am ---[I looked at that picture again and to be honest one will have a very hard time convincing me those brackets are not made out of aluminium.
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By looking at the posted picture I have to agree. I did not have a picture of my unit of that area where they are mounted at the time of my earlier post, but will probably pull it from the rack sometime this week to replace the fan thermostat that I added with a lower temperature trip point one, so will have a chance to examine those brackets more closely.
Also agree that aluminum oxide (white powdery stuff) is non-conducting, so not a desirable compound to be present at electrical connections.
AVGresponding:
The oxide layer is pretty transparent at the few nanometres of thickness it has, and covers the whole surface. The only way to get a clean, pure surface, is to use a chemical cleaner, and it doesn't last very long. This is one reason that despite the much lower cost of aluminium, copper is still preferred for most electrical local supply installations (it is used for grid and supergrid, but that's a different story) because it's very troublesome to get a proper termination; you can't just make off an armoured cable and shove the ends into a connector block or crimp, you have to use special materials and techniques, and the connection is still more likely to cause problems over time.
When you stick your DMM probe on an exposed bit of aluminium frame or bracket, your probe tip breaks through the oxide layer. When inserts are crimped into an Al part, the electrical connection relies on displacing material to ensure a mating surface that is not exposed to atmosphere. It's still just a matter of time before they fail, and it won't necessarily be visually obvious, unlike with say, a rusty steel or iron part.
AMR Labs:
I think for aluminum to oxidize the environment has to be quite damp (possibly even wet), probably not the case inside this instrument unless it is being stored somewhere humid enough, and then aluminum oxide forming would be the least of the worries. Most of the aluminum oxide I've seen in general is usually caused by electrolysis (aided by dampness) for example between a stainless steel screw driven into aluminum. In those cases most times the screw is so tight that it will not turn so that for removal one usually needs to shear it off and drill a new hole for the next screw. But I diverge.
Bud:
--- Quote from: AVGresponding on January 24, 2023, 10:13:33 am ---It's still just a matter of time before they fail, and it won't necessarily be visually obvious, unlike with say, a rusty steel or iron part.
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I once had a factory made 100W RF amplifier, about 30 years old. The input and output connectors were riveted to the rear aluminum panel, yet none of them made electrical contact with the panel :scared:
AMR Labs:
--- Quote from: Bud on January 24, 2023, 02:42:30 pm ---
--- Quote from: AVGresponding on January 24, 2023, 10:13:33 am ---It's still just a matter of time before they fail, and it won't necessarily be visually obvious, unlike with say, a rusty steel or iron part.
--- End quote ---
I once had a factory made 100W RF amplifier, about 30 years old. The input and output connectors were riveted to the rear aluminum panel, yet none of them made electrical contact with the panel :scared:
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The probably anodized aluminum panel, as many similar radio equipment of their time used, and on which those connectors where mounted, did surely not help much with proper contact either. By using rivets instead of proper screws/nuts with star washers obviously points to that manufacturer wanting to skimp on costs and not really caring much about long term reliability.
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