[N_Cook]

Bill wrote in message
...
On 10/6/2011 10:46 AM, Dave Heil wrote:
On 10/5/2011 15 35, Jeffrey Angus wrote:
On 10/5/2011 10:16 AM, N_Cook wrote:
No etching of this material. Plain board , punched to take eyelets and
then
wires or component leads fed through the eyelet and soldered. Very
dark grey
almost black , well 40-50 years on it is

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.

It is indeed fish paper and a really heavy version of it. I've seen a
number of amps where it has held up well. I'd guess these were stored
not in garages or basements but in interior rooms or closets.

will a penetrating epoxy poured onto it fix the problem? it would at
least prevent/block moisture.


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.

[Bill[_42_]]

On 10/7/2011 12:36 AM, N_Cook wrote:
wrote in message
...
On 10/6/2011 10:46 AM, Dave Heil wrote:
On 10/5/2011 15 35, Jeffrey Angus wrote:
On 10/5/2011 10:16 AM, N_Cook wrote:
No etching of this material. Plain board , punched to take eyelets and
then
wires or component leads fed through the eyelet and soldered. Very
dark grey
almost black , well 40-50 years on it is

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.

It is indeed fish paper and a really heavy version of it. I've seen a
number of amps where it has held up well. I'd guess these were stored
not in garages or basements but in interior rooms or closets.

will a penetrating epoxy poured onto it fix the problem? it would at
least prevent/block moisture.


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

[N_Cook]

Bill wrote in message
...
On 10/7/2011 12:36 AM, N_Cook wrote:
wrote in message
...
On 10/6/2011 10:46 AM, Dave Heil wrote:
On 10/5/2011 15 35, Jeffrey Angus wrote:
On 10/5/2011 10:16 AM, N_Cook wrote:
No etching of this material. Plain board , punched to take eyelets
and
then
wires or component leads fed through the eyelet and soldered. Very
dark grey
almost black , well 40-50 years on it is

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.

It is indeed fish paper and a really heavy version of it. I've seen a
number of amps where it has held up well. I'd guess these were stored
not in garages or basements but in interior rooms or closets.

will a penetrating epoxy poured onto it fix the problem? it would
at
least prevent/block moisture.


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

But any conductive pathway in the core would remain unaffected

[dave]

On Sat, 08 Oct 2011 08:07:32 +0100, N_Cook wrote:

Bill wrote in message
...
On 10/7/2011 12:36 AM, N_Cook wrote:
wrote in message
...
On 10/6/2011 10:46 AM, Dave Heil wrote:
On 10/5/2011 15 35, Jeffrey Angus wrote:
On 10/5/2011 10:16 AM, N_Cook wrote:
No etching of this material. Plain board , punched to take
eyelets
and
then
wires or component leads fed through the eyelet and soldered.
Very dark grey
almost black , well 40-50 years on it is

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.

It is indeed fish paper and a really heavy version of it. I've seen
a number of amps where it has held up well. I'd guess these were
stored not in garages or basements but in interior rooms or
closets.

will a penetrating epoxy poured onto it fix the problem? it
would
at
least prevent/block moisture.


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

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.

[Jeffrey Angus[_2_]]

On 10/8/2011 9:04 AM, dave wrote:
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"

[N_Cook]

Jeffrey Angus wrote in message
...
On 10/8/2011 9:04 AM, dave wrote:
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