Material for Turret Board

[drz400]

It may work for certain electrical motor aplications because of it's resistance to heat but compared to FR4 it is hygroscopic which can lead to some snap crackle pop 10 years later or when exposed to humid condictions. Not all micarta is made the same
You can find some that is 2% hygroscopic and some that is 1%. FR4 is the standard for PCB use and is .25% hygroscopic

The laminates they are using now, which are seeing extensive use in all sorts of immersed conditions, seem to be holding up pretty well- and that's under hard day-to-day use, exposed. If I had any doubts about the material, I'd laminate with marine or some similar structural epoxy.
.

taken up and retained under some conditions of humidity and temperature <hygroscopic water in clay>
- hy·gro·scop·ic·i·ty /-(")skä-'pi-s&-tE/ noun

I'm not talking about the strength or ability of the board holding together when wet. I'm talking about noise, the unwanted and puzzling kind. Boards that are hygroscopic pick up moisture easier. In an old Fender amp the Vulcanized fiberboard was hygroscopic but easy to work with (can be laser cut as well) the problem is that eventually the amps started to make noises. Fender later learned the solution was to wax the boards (with components)
I see no reason to risk an amp making noises 2 years after I built it when the material like FR4 are around. There is a reason FR4 is the material of choice for PCB's

[Ears]

It may work for certain electrical motor aplications because of it's resistance to heat but compared to FR4 it is hygroscopic which can lead to some snap crackle pop 10 years later or when exposed to humid condictions. Not all micarta is made the same
You can find some that is 2% hygroscopic and some that is 1%. FR4 is the standard for PCB use and is .25% hygroscopic

This website and links to data sheets claims water absorbtion is the same for G10 and FR4 and that the only difference is fire rating;

http://www.jjorly.com/g10_fr4_sheets_fabricator.htm

It describes Micarta as having glass fibre (I had thought it was cloth). Does it depend on manufacturer?

Micarta is good enough for NASA <smile>

[titanicslim]

As far as I know (and I don't have time to look it up) Micarta is the proprietary name for a variety of laminates of varying strengths and thermal characteristics. In fact, they are, or at least used to be, very willing to work with customers in tailoring the product to meet your specific needs. I think you pay a little extra for that. You can most assuredly get Micarta that will make heroic circuit boards, and that's off the shelf.

I was talking about something far less over-engineered but, I think, entirely able to perform well for as long as the thing will be viable in all other respects, and that's Formica. I will use products of this nature because they're cheap and Garolite's overpriced, because I am confident that I can adequately prepare them with, for example, resourcinol- thanks to the active... er, functioning mind of Skyboltone- and because it will be streets ahead of the stuff Leo and many others used, and that we all know is deficient but still worked like an aa764.

Dave

[skyboltone]

Ain't it grand that these discussions get so much mileage? I'd use formica in a heartbeat. I looked at Tap Plastics for something suitable and couldn't decide that anything they had would resist the heat and insulate well enough to do the job I wanted. I used to have about a 36X48 sheet of that red swirly fiberglass board that is used between sections of motor control centers to keep arc flash from spreading from one section of buss to another in the event of a Ozone assisted arc. I just got tired of the glass splinters in my hands everytime I used the stuff. I still have a couple of hunks of some kind of micarta that I salvaged out of the power supply sections of AM broadcast transmitters from the '50s. The problem in those babys was never very complicated. The oil filled caps just blew up or tube sockets would arc track from corona effect. Running 2800-3KV on the plates. Ocassionally a transformer secondary would go to case on the plate or output transformer. Then you just mount the damn thing on a hunk of plywood and write "Case Hot" in grease pencil on the culprit. Time was money and the station manager really didn't give a shit what you used. Just get back on the air.

I guess if a guy was really worried about snaps and crackles the first thing he ought to do is quit using Alpha pots. Then maybe go after the chinese ceramic sockets.

Oh well, what the heck. This subject is probably good for another 2 or 3 hundred entrys before it peters out. Let's talk about eyelet tools some more. I made mine out of the screw from a conduit beam clamp, two washers and a nut. It fits in the hole in my drill press. I use a sawed off 16 penny nail chucked up tight for the mash effect. Didn't cost nothin'

I hate drilling aluminum with unibits. There's always way too much burr on the bottom side of the hole. Get a good set of Forstner Bits and use and aluminum tapping compound (Tap-eze?) and turn the drill slow. Also start with a 1/16th pilot hole. A forstner tip is meant only to center in wood, not make holes in soft metals. Carves beautiful holes ready to mount hardware. Screw IEC power connectors. I hate making the hole for them. Same with those little switches from mountain and others. What are we midgets? I'm gonna get me a wood burning kit and make a few front panels like KF. What else can we fight about? I'm getting pretty pissed off at NOS tube dealers who lie and cheat. In the old west they'd catch a bullet for their trouble. Why doesn't the index at Mouser not mention Hexfred but Digikey is full of it. What does it all mean anyway. Wanna see some pictures of my dogs? [img:574:480]http://tinypic.com/2d7v58m.jpg[/img] The one in the middle is the mean one.

[heisthl]

Which dog is your sig pic dog?
I'm still thinking that at less than $25 for a 24 x 24 sheet the McMaster garolite is worth it. That enough for at least 12 amp builds. Besides, you'll save that much when you order the screws,bolts,nuts(they have the ones with tooth lock washer attached!) and finish washers from the same place.
Harbor Freight has a 3 piece unibit (titanium coated) for less than $9 and if you time it right and switch the drill direction at exactly the last second, no burring.

[skyboltone]

Which dog is your sig pic dog? He's just a good lookin' mutt I found on the internet. Big male, lot's of attitude. My red dobie girl there on the left just won't take a picture worth a darn. I think when you point something at her she thinks she's in trouble. I don't know why, she's never been struck with so much as a newspaper. Potty trained herself.
I'm still thinking that at less than $25 for a 24 x 24 sheet the McMaster garolite is worth it. That enough for at least 12 amp builds. Besides, you'll save that much when you order the screws,bolts,nuts(they have the ones with tooth lock washer attached!) and finish washers from the same place. I couldn't agree more, sheesh. Harbor Freight has a 3 piece unibit (titanium coated) for less than $9 and if you time it right and switch the drill direction at exactly the last second, no burring. Now there's one I hadn't heard. I'll try it.

[statorvane]

I hate drilling aluminum with unibits. There's always way too much burr on the bottom side of the hole.

Yes, this is a problem. I have found that after drilling the holes, I can easily deburr them by manually rotating the bit from the back side of the hole. Shears off any residual burr.

Nice looking bunch there guy. I'd watch out for the one in the middle though - she looks like trouble !

[drz400]

It may work for certain electrical motor aplications because of it's resistance to heat but compared to FR4 it is hygroscopic which can lead to some snap crackle pop 10 years later or when exposed to humid condictions. Not all micarta is made the same
You can find some that is 2% hygroscopic and some that is 1%. FR4 is the standard for PCB use and is .25% hygroscopic

This website and links to data sheets claims water absorbtion is the same for G10 and FR4 and that the only difference is fire rating;

http://www.jjorly.com/g10_fr4_sheets_fabricator.htm

It describes Micarta as having glass fibre (I had thought it was cloth). Does it depend on manufacturer?

Micarta is good enough for NASA <smile>

The problem here and what I'm trying to say is that "Micarta" is not really a material but a series of trademarked products, when many companies sell you Micarta it is paper based and really not recommended IMO for tube amplification unless you wax the PCB.

So as I said "Micarta" is not really a description of a specific product but a range of products, some too hygroscopic.

"Micarta industrial laminates are normally phenolic, epoxy, silicone, or melamine resin based thermoset materials reinforced with fiberglass, cotton cloth, paper, or carbon fiber. Micarta industrial laminate sheet is a hard, dense material made by applying heat and pressure to layers of prepreg. These layers of laminations are usually of cellulose paper, cotton fabrics, synthetic yarn fabrics, glass fabrics or unwoven fabrics."

FR4 material conforms to the requirements of military specification Mil P 13949 Type F, MIL-S-13949/04 GF/GFN/GFK and Mil I 24768/2 and is rated UL 94V-O. FR4 material is also known as Garolite. However...
McMaster Carr has 11 different Garolite options, some excellent for PCB uses, some suck and are paper based.

So from your source they have 3 different Micartas, CE, LE and the FR4

36*48 FR4 for $116 will get you a lot of PCB's, if one is going to fret over expensive caps and resistors I see no reason to cut corners especially when it isnt an easy replacement. Just my opinion

[heisthl]

I use McMaster 85345K631 GRADE G-10/FR4 COLORED GAROLITE SHEET, 1/16" THICK, 24" X 24", BLACK $24.88 for 24 X 24.