The larger resistors were warm enough to smoke. What do you think these small ones will handle 4 Watts for a minute?It's not all about size.
The video for the remaining tests of the Fluke 87V are now on-line. Enjoy.Thanks Joe for the HVDC tests on the MOVs - although uneventful, they show how a good design can withstand some overvoltage (it was not the case of my old deceased meter).
The selector grinding really looks ugly and surprising to such an expensive Fluke. In my opinion the 87V still does not deserve any endurance prize when compared to some of its cheaper brethren.
Very interesting outcome. Makes it clear that it’s not a problem with the fundamental design. I think the previous failure was just a fluke.
The fact it was an old meter with no dependable record of its history leaves open the possibility those components had already been stressed to the point of failing prior to the test being run. I suspect the result using the repaired meter (with new diodes) is more typical of what you may expect.
The fascinating thing to me is the apparent ease with which you manage to repair a blown up meter
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From a mechanical standpoint, I don't like the 87V switch wear but it was making good contact and still better than most of the meters I have looked at.
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Today, after almost three years, we set a new milestone with this thread. The admins were called in to censor a few posts. To try and avoid future problems, I have updated the first post to include some basic rules and guidelines to follow if you plan to post on my YT channel.
Today, after almost three years, we set a new milestone with this thread. The admins were called in to censor a few posts. To try and avoid future problems, I have updated the first post to include some basic rules and guidelines to follow if you plan to post on my YT channel.Wow, that is quite odd. The discussion was quite civil in my opinion. Perhaps there is no desire to criss cross feuds happening in another platform. Oh well... Back to your normal programming I guess.
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From a mechanical standpoint, I don't like the 87V switch wear but it was making good contact and still better than most of the meters I have looked at.
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As an 87V owner I was also surprised and concerned by the awful rough movement developing in the rotary switch, although it's difficult to make sense of what is happening (how it 'feels') based on the sound as reproduced on the video. I gave it some thought and suspect it is the result of two things: the spring contacts being slightly 'loose' in their housing (by 'loose' I mean the tension holding it in place may be lower than optimal), and secondly the fact you use a constant speed when turning the switch on your jig. I would suggest the latter, in combination with the less than secure spring retention, allowed a sympathetic chattering to develop.
Chattering will be dependant on a number of factors: the amount of friction between spring contact face with plated track, the surface area of the contact face (which will increase as small flats are worn into them as they bed in), and the base spring tension pressing the two components together (oh, and speed!). If the spring retention mechanism allows enough flexibility such that friction overcomes its ability to slide smoothly (and thus sticks for a fraction of a second) then you will get sympathetic chattering, however this will be exacerbated by using a constant speed allowing the pattern to be imprinted into the track itself. Once established there will be positive feedback and things will only get worse as the procedure continues. Note that a lubricated track may have reduced the friction to the point where sticking would not occur - but all the other factors need to be in place before this would become a critical factor.
(There are similarities with using a parting tool in the lathe, the factors that cause chattering are similar, and if nothing can be done about the stiffness of tool mounting or play in headstock bearings then adding lubrication and/or adjusting cutting speed often resolves the problem)
Such perfectly constant speed provided by your test jig is not something that is seen in real life when simply turning the switch manually, so the chances of developing such a pattern of chattering will therefore be reduced. I do understand your idea about reducing the possibility of heat being generated due to turning the switch too rapidly but I also think you should vary the speed too.
It may be too late for that test example now (given the state of the tracks), but perhaps re-tensioning the spring contacts so they are held in place more firmly, a few seconds on a buffing wheel to round off any sharp flats formed on the spring contact faces, and perhaps a little lubrication would restore proper function.
It might be worth investigating where the dial noise comes from.
eg. Put some very viscous grease in the white switch dial thing to dampen any movement of the contact springs where they touch it.
This would let you know if the noise comes from PCB scraping or rattling of the springs in the housing.
chrimony
4 hours ago
@6:10 Surprised to see the plasma outside the bulb.?
Getting ready to look at another meter. I've been busy repairing an old scope that a friend of mine gave me that happens to be just like one I had given away a few years ago. I have finished it up but have some cleanup to do along with some other spring time work that needs to get done but I hope to get started this weekend.
Again, I want to than those of you who have offered to pitch in and buy me this meter to run, or out right offered to pay for it. I appreciate the gesture. Maybe one day I will open some sort of account to allow people to donate. For now, consider the small bit of data I supply as my way of giving back to the technical community.
Yes, the meter is here.. It looks scared..