circuit board material of the 1960s

Phenolic.

--
You can't have a sense of humor, if you have no sense.

component

So is it dyed phenolic? I only ever see brown phenolic material and more rigid, for the thickness, than this Fender stuff. Next time I come across some of it I'll burn a sample - unmistakable smell if phenolic.

This is what the board looks like and as it is used, colour is correct

Will quite readily bend when cold , say .5 inch displacement over a 2 inch run although something like 1/8 inch thick

I believe what you're referring to is called "fish paper". A heavy, stiff grey/black cardboard.

Phenolic was between orange and brown, considerably stiffer and would crack if bent. Commonly used at the time for those tag strips. Having rows of turret terminals down both sides.

A lot of "That turned out to be a bad idea" techniques were attempted in the late '50s through the early '70s to eliminate point to point chassis wiring.

Not all items, and especially "consumer" items were designed with the idea "This should last forever". That as many items built as far back as the '20s are still serviceable is more by accident and over engineering that by conscience design.

Jeff

--
"Everything from Crackers to Coffins"

t

What color is it and how thick is it?

Circuit boards in general "go bad" because they absorb moisture, they fail mechanically because of stress from soldered parts or the weight of soldered parts, they become covered with conductive filth, or they arc-track because of sustained high voltages.

That's too small and too poorly lit to be very useful. An image 300% the size would have been better.

Jeffrey Angus wrote:

That's the closest thing that matches the description, but the thickest stuff I've seen is nowhere near 0.125".

As spamtrap alluded to, without some kind of coating, this stuff sucks up moisture.

"Michael A. Turd"

** Brrrrraaaapp WRONG !!

.... Phil

"spamtrap1888"

What color is it and how thick is it?

** Grey, about 0.5mm thick.

Circuit boards in general "go bad" because they absorb moisture,

** This stuff is a moisture absorber - something well known to Fender and others who used it.

Sooo, they hot impregnated it with wax !!!

The KOOK has failed to mention this crucial fact.

The hot wax treatment is not 100% effective and if the item is left in damp storage for a long time, moisture gets into the material. Re-heating and melting the wax has no good effect.

The material is like stiff cardboard and was used as SECONDARY electrical insulation in transformers, ie to separate windings from the core.

Such transformers were vacuum impregnated in varnish after manufacture which made the grey material insulate OK.

... Phil

Is it your lunch time already, Phyllis?

--
You can't have a sense of humor, if you have no sense.

En el artículo , N_Cook escribió:

Paxolin?

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(='.'=) 
(")_(")

So if its vulcanised fibre board and I burnt a sample of it would it have a rubber smell ? If it was a paxolin type material then the phenolic smell if burnt would be a pretty sure indicator

Searching "vulcanized fiber board" will reveal many suppliers of this cellulose material.

I've recently seen a couple of US sources where this VFB material can be purchased.. Stew Mac for making guitar pickups or other items, and Antique Electronic Supply for using as general insulating material.

The VFB material has long been used for making switches, terminal boards and numerous applications where Bakelite or other materials had previously been used.

VFB is typically die-cut to shape and holes are generally punched during the same operation.

A different, flexible material is "insulating cambric" which can be sheet material or tubing.. often amber in color, and often placed between terminals and surrounding parts.

There are basically no perfect insulators, only some that are better than others, and most importantly in recent decades, some that are cheaper than others.

-- Cheers, WB .............

e

I see AES sells tag and turret boards made of more reasonable looking material. Search here:

It requires some knowledge of the failure mode first, which so far in this thread has not been explored. Because of its microphonic behaviour I suspect some sort of capacitance efffect. Hinted at by it only seems necessary to separate the "active" board and the backing insulation "grounded" board to stop the rustle and microphony. More permanent fix by securing some rigid paxolin FRPB between the 2 boards. I suspect something in the core of the material goes conductive enough to create a capacitor surface around high voltage points.

my guess about the penetrating epoxy is that it would turn the stuff into a sort of instant FRP

and

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But any conductive pathway in the core would remain unaffected

Bake in 250 degree oven for 2 hours first, allow to cool naturally, then seal.

How does that fix any carbon pathing that developed?

Jeff

--
"Everything from Crackers to Coffins"

I had also assumed the problem although initially through humidity take-up , the rustling (rather than a louder crackling ) problem, I could only see as microscopic discharges somewhere in the core of the material. Separating the 2 boards with PRFB and insulating the fixing screw that passes between the 2 stops it , presumably because the pd through the short run of board to the ground is now a longer path - not cured , just delayed. If you knew where the conductive paths were , it may be possible to route/grind slots into the board to cure or preclude these problems