Yes.
sqr(480000 / 10.95)
209 ohms.
L looks a bit high. It could be right, but try this:
Connect it up again, get the value, then short at the meter/wire junction. Subtract that from the 3.8uH, recalc.
jn
hitswire,
Do you really even know what Bakelite is? That is a trade name for a composite material made with phenolic resin. Still used today in lots of places without that name attached. I'm sure that Sy can school us all in the properties of that material.
Do you really even know what Bakelite is? That is a trade name for a composite material made with phenolic resin. Still used today in lots of places without that name attached. I'm sure that Sy can school us all in the properties of that material.
In the case of Nick Tesla I have to agree. The difference between nuts and genius is how profitable the idea is !
The circuit board material is a laminate of paper impregnated with phenolic resin. I think it's a bit more hygroscopic compared to the glass/epoxy laminates. Personally I think it's just fine and would like to use it, but when I contacted several board houses here in the US, none of them had even heard of it.
se
Its called CEM
Composite epoxy material - Wikipedia, the free encyclopedia
For cheap single sided projects you can stamp the holes and board outline.
Bakelite is also why PCBs are 1/16" thick.
Composite epoxy material - Wikipedia, the free encyclopedia
For cheap single sided projects you can stamp the holes and board outline.
Bakelite is also why PCBs are 1/16" thick.
SE,
Not so sure about whether the paper phenolic would be more hygroscopic than glass epoxy, but I will give you that the glass epoxy should be stronger in a shear application. Phenol resins are used in aerospace applications I believe due to the high heat distortion properties and resistance to burn, I think they char and somewhat self extinguish but it has been years since I talked to my friend who sold those chemicals. If I remember correctly the glass fibers in the trimmed edges of a glass/epoxy laminate are hygroscopic in nature. One of the failure modes of that material under certain conditions if again I am remembering correctly.
Where is Sy when we need him! 😀
Not so sure about whether the paper phenolic would be more hygroscopic than glass epoxy, but I will give you that the glass epoxy should be stronger in a shear application. Phenol resins are used in aerospace applications I believe due to the high heat distortion properties and resistance to burn, I think they char and somewhat self extinguish but it has been years since I talked to my friend who sold those chemicals. If I remember correctly the glass fibers in the trimmed edges of a glass/epoxy laminate are hygroscopic in nature. One of the failure modes of that material under certain conditions if again I am remembering correctly.
Where is Sy when we need him! 😀
Paper is definitely more hygroscopic than glass. 😀 We used to call this stuff "fishplate," and some years ago, it was the standard PCB and terminal board material. For a variety of reasons (changing economics, regulation, and large-scale commercial use of high speed digital signals), it's been displaced by epoxy.
The reality is that this is usually not terribly important at audio frequencies and low impedances. Nor at higher frequencies- there's plenty of vintage ham equipment out there with phenolic board that still works fine. Some claim sonic differences, but with the usual lack of any real evidence. In the extreme, people have used PTFE boards, which are great for electrometers, but have severely compromised reliability and mechanical properties.
You remember correctly. This is exacerbated by the coupling agents used to get the fibers to stick to the resin.
The reality is that this is usually not terribly important at audio frequencies and low impedances. Nor at higher frequencies- there's plenty of vintage ham equipment out there with phenolic board that still works fine. Some claim sonic differences, but with the usual lack of any real evidence. In the extreme, people have used PTFE boards, which are great for electrometers, but have severely compromised reliability and mechanical properties.
You remember correctly. This is exacerbated by the coupling agents used to get the fibers to stick to the resin.
Measured L is OK.
Thank you.
I measured as you suggested. I measured several inductors for passive xovers that I have on hand and seems the LCR measures OK.
Thanks for your time & kind advice.
Good luck. If you have any other q's regarding how to do it, PMA's your man..
jn
Al the PCBs from aircraft electronic boxes I have seen are all heavily varnished after assembly for moisture proofing, both the old boards made of Bakelite and newer made of class epoxy. No edges and no holes are exposed and they are made to remain unexposed during service life.
As for the glass fiber and carbon fiber composite larger constructions, you are correct. One of the failure modes is due to ingress of moisture. Not because the glass or carbon are hydroscopic themselves.
It is that the “fibers” are actually bundles of many single fibers of minute diameter. Moisture enters through capillary action:
- between these single fibers within each bundle where the edges are exposed (ends of panels and drilled hole wells when sealant has been damaged or not properly applied ).
-between fiber bundles and resin after prolonged mechanical stressing or sudden strong impact.
This trapped moisture turns into ice at high altitudes, increasing it’s volume and causing local damage which after many flight cycles increases it’s area, ending in reduced load carrying structures. Structural damage manifests itself macroscopically as fiber bundles multi-cracking and severe delamination.
George
I know it's the brown very breakable material
used for boards in the cheapest devices.
As opposed to fibreglass used in more quality
conscious equipment.
‘Coupling agents’ (called ‘formers’), are applied over each single fiber immediately after pulling.
At least today, this term describes processes where chemical reactions are utilised to alter the surface energy of the fibers.
I haven’t read anything assigning hydroscopic properties to ‘formers’. If you have any link, pls send it to me.
George
George,
Yes I know about 3K and 6K and other bundle sizes used for composite construction. And working with both wet layup and prepregs am aware of the limitations of many of these materials. I worked in advanced composites using polyurethane resins and one of the major problems was the lack of a sizing that was compatible with the resin system. Things have changed in the last 25 years so I believe that problem has been addressed since then. Most of the sizing was for either epoxy or polyester resins at the time. We were Sh*t out of luck at the time as Owens Corning and the others couldn't be bothered at the time to make a special run of fiber material just for our use, even though I was working with Bayer on this problem at the time.
ps. Your use of the term coupling agent matches what we call sizing here in the States.
Yes I know about 3K and 6K and other bundle sizes used for composite construction. And working with both wet layup and prepregs am aware of the limitations of many of these materials. I worked in advanced composites using polyurethane resins and one of the major problems was the lack of a sizing that was compatible with the resin system. Things have changed in the last 25 years so I believe that problem has been addressed since then. Most of the sizing was for either epoxy or polyester resins at the time. We were Sh*t out of luck at the time as Owens Corning and the others couldn't be bothered at the time to make a special run of fiber material just for our use, even though I was working with Bayer on this problem at the time.
ps. Your use of the term coupling agent matches what we call sizing here in the States.
Now back to John's comment about the 1/3 power test and why he thinks that is a false or misleading test please.
There's different grades. The more expensive ones have fallen out of use because of the changing market with only the cheapest ones remaining, but for many decades, you could get superb quality phenolic board.
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