Carbon Comp: Aging Causes Out Of Tol?

"Walter Harley" <walterh@cafewalterNOSPAM.com> wrote in message
news:9LednWF97e5xDhrfRVn-pg@speakeasy.net...

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com
wrote
in message news:118ef69isc5dp88@corp.supernews.com...
Over 14 years, would drift from aging cause them to go
that far out of tolerance?

I was recently working on an amp from the 1950's; every carbon comp in
it
was at least 20% higher than its markings indicated.

(Woe be unto the tech who repairs a tube guitar amp and replaces the
resistors with new ones whose values are nominally correct! Depending
on
which resistor it is, it'll change the sound of the amp...)

For the old toob amps., 20% wasn't all that disastrous. As long as the
change wasn't caused by heat. Since those amps get hot, the half watt
resistor is probably only capable of dissipating half that, because it's
in a hot environment. Could be that the vents were inadequate or were
plugged up with dust and spider webs.

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote:

"mike" <spamme0@netscape.net> wrote in message
news:428785D4.8000206@netscape.net...

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote:

I have fifty 910 ohm 1/4W carbon composition resistors, still in the
paper tape, which is labeled:

OHMITE
910 OHM
1/4 W 5%
RC07GF911J
OC9115

Judging from the last line, they're 14 years old. They've never

been

used, AKA New Old Stock. Every resistor measures greater than 5%,

some

are over 1k. Over 14 years, would drift from aging cause them to go
that far out of tolerance? I have carbon film resistore much older

than

these and they still measure within 5% tolerance, usually within 2%.


I think this is common.
I bought a box of 1000 114 ohm resistors. Stackpole Mfg Date 1980.
Unfortunately, they're marked 100 Ohm 5%. Was gonna use 'em
in pairs to terminate 50 Ohm transmission lines...oh well...
I should try cooking them to see if they change back.
mike


Hey, YEAH! Great idea! I'll hold a couple over the soldering iron and
see if they stay changed when they cool off. It won't hurt to mess up a
few, since they're already messed up to begin with. ;-)

BRB...

Well, that didn't help. I took four of them and layed each on the
soldering iron. Each went up several dozen ohme, some between 1050 and
1100. And they stayed at that value when cool. :-(

Don't think that works. Need to use low heat for long term. Put some
atop that big CRT monitor for a few weeks. Mine's hot enough to bake
bread. ;-)

There's another issue that comes to play on older resistors.
Back in the day, they cranked out resistors and marked 'em whatever they
measured. 5% resistors were selected out. Then the 10%ers. What was
left was 20%. End result was that a 20% resistor was hardly ever
within 10%. For each tolerance, you got a bi-modal distribution
with a hole where the good stuff was taken out.
mike

Just put a 470 ohm resistor in parallel with the two 114 ohms, and
you'll have 50.8 ohms, which is just about right.

Long ago, in a galaxy far, far away, I scrounged a dummy load out of a
cardboard store display for a CB xcvr. They used a 50 ohm 5W wirewound
resistor, and put a capacitor, I think it was 47 pF, in series to series
resonate with the wirewound resistor's inductance and cancel it out.
Worked just fine.


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On Sun, 15 May 2005 05:13:49 -0700 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

I have fifty 910 ohm 1/4W carbon composition resistors, still in the
paper tape, which is labeled:

OHMITE
910 OHM
1/4 W 5%
RC07GF911J
OC9115

Judging from the last line, they're 14 years old. They've never been
used, AKA New Old Stock. Every resistor measures greater than 5%, some
are over 1k. Over 14 years, would drift from aging cause them to go
that far out of tolerance? I have carbon film resistore much older than
these and they still measure within 5% tolerance, usually within 2%.

If you could find an old Allen-Bradley catalog you'd be truly amazed
at the amount of detail they lay out on the moisture sensitivity of
these resistors.

The gist of it is as follows:

1) Carbon composition resistors will absorb moisture out of the air
and go up in resistance. If the resistance is important to the
manufacturer, they much keep them in a special dry engvironment, just
like flux coated welding rods.

2) If you have carbon composition resistors which have gotten damp,
they can be dryed out by heating them to temps below 100C for several
days. 2 Watters take longer than 1/4 Watters. Don't try to speed this
up by using higher temps.

3) If you solder them when they are "damp" the change in resistance
will be locked in, ie no longer reversible.


I did this test on a batch of 27k, 2W carbon comp resistors a number
of years ago. They were all high, and most of them were out of
tolerance, this was immediately as purchased from Newark. But they all
came back into tolerance after heating in my home-made oven for about
a week.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

"Watson A.Name - "Watt Sun, the Dark Remover"" <NOSPAM@dslextreme.com> wrote
in message news:118f8qbc5pepsc4@corp.supernews.com...

"mike" <spamme0@netscape.net> wrote in message
news:428785D4.8000206@netscape.net...
Watson A.Name - \"Watt Sun, the Dark Remover\" wrote:
I have fifty 910 ohm 1/4W carbon composition resistors, still in the
paper tape, which is labeled:

OHMITE
910 OHM
1/4 W 5%
RC07GF911J
OC9115

Judging from the last line, they're 14 years old. They've never
been
used, AKA New Old Stock. Every resistor measures greater than 5%,
some
are over 1k. Over 14 years, would drift from aging cause them to go
that far out of tolerance? I have carbon film resistore much older
than
these and they still measure within 5% tolerance, usually within 2%.

I think this is common.
I bought a box of 1000 114 ohm resistors. Stackpole Mfg Date 1980.
Unfortunately, they're marked 100 Ohm 5%. Was gonna use 'em
in pairs to terminate 50 Ohm transmission lines...oh well...
I should try cooking them to see if they change back.
mike

Hey, YEAH! Great idea! I'll hold a couple over the soldering iron and
see if they stay changed when they cool off. It won't hurt to mess up a
few, since they're already messed up to begin with. ;-)

BRB...

Well, that didn't help. I took four of them and layed each on the
soldering iron. Each went up several dozen ohme, some between 1050 and
1100. And they stayed at that value when cool. :-(

< snip >

It's been a long time since I did the math, but IIRC, when you added up all
the tolerances, milspec carbon comps could vary in-circuit by 41.4% of their
stated value and still be within spec.



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Date: Mon, 16 May 2005 17:55:33 GMT

On 13 May 2005 15:51:49 -0700, "stevem@citlink.net"
<stevenm@uneedspeed.net> wrote:

None of the South's better generals, however, fought to preserve
slavery. Niether Robert E. Lee nor Stonewall Jackson, nor Jeb Stuart,
nor George Johnston were slave owners.

Is that right? How do you account for this:
http://www.sonofthesouth.net/leefoun...es%20slave.htm

I can't find anything in a cursory online search about Jackson owning
slaves, but his family certainly did:
http://en.wikipedia.org/wiki/Stonewall_Jackson

....as was JEB Stuart: http://www.jebstuart.org/history.cfm

Don't know George Johnston. If you mean Joe Johnston, I can't find
anything online with another cursory search. Not going to try very
hard; the side he picked speaks for itself.

They thought the institution abhorent.

Obviously not.

"mike" <spamme0@netscape.net> wrote in message
news:4287F5D1.5040107@netscape.net...

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote:
"mike" <spamme0@netscape.net> wrote in message
news:428785D4.8000206@netscape.net...

Watson A.Name - \"Watt Sun, the Dark Remover\" wrote:

I have fifty 910 ohm 1/4W carbon composition resistors, still in
the
paper tape, which is labeled:

OHMITE
910 OHM
1/4 W 5%
RC07GF911J
OC9115

Judging from the last line, they're 14 years old. They've never

been

used, AKA New Old Stock. Every resistor measures greater than 5%,

some

are over 1k. Over 14 years, would drift from aging cause them to
go
that far out of tolerance? I have carbon film resistore much older

than

these and they still measure within 5% tolerance, usually within
2%.


I think this is common.
I bought a box of 1000 114 ohm resistors. Stackpole Mfg Date 1980.
Unfortunately, they're marked 100 Ohm 5%. Was gonna use 'em
in pairs to terminate 50 Ohm transmission lines...oh well...
I should try cooking them to see if they change back.
mike


Hey, YEAH! Great idea! I'll hold a couple over the soldering iron
and
see if they stay changed when they cool off. It won't hurt to mess
up a
few, since they're already messed up to begin with. ;-)

BRB...

Well, that didn't help. I took four of them and layed each on the
soldering iron. Each went up several dozen ohme, some between 1050
and
1100. And they stayed at that value when cool. :-(

Don't think that works. Need to use low heat for long term. Put some
atop that big CRT monitor for a few weeks. Mine's hot enough to bake
bread. ;-)

I've got a LCD panel, doesn't get warm. :-(

There's another issue that comes to play on older resistors.
Back in the day, they cranked out resistors and marked 'em whatever
they
measured. 5% resistors were selected out. Then the 10%ers. What was
left was 20%. End result was that a 20% resistor was hardly ever
within 10%. For each tolerance, you got a bi-modal distribution
with a hole where the good stuff was taken out.
mike

Yeah, I've seen that with some parts. Sucks big time if you're
depending on getting good parts. Thanks.

"Jim Adney" <jadney@vwtype3.org> wrote in message
news:8vvf819a1qo9d84a9c4kqggcjumo2pg0hc@4ax.com...

On Sun, 15 May 2005 05:13:49 -0700 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

I have fifty 910 ohm 1/4W carbon composition resistors, still in the
paper tape, which is labeled:

OHMITE
910 OHM
1/4 W 5%
RC07GF911J
OC9115

Judging from the last line, they're 14 years old. They've never been
used, AKA New Old Stock. Every resistor measures greater than 5%,
some
are over 1k. Over 14 years, would drift from aging cause them to go
that far out of tolerance? I have carbon film resistore much older
than
these and they still measure within 5% tolerance, usually within 2%.

If you could find an old Allen-Bradley catalog you'd be truly amazed
at the amount of detail they lay out on the moisture sensitivity of
these resistors.

The gist of it is as follows:

1) Carbon composition resistors will absorb moisture out of the air
and go up in resistance. If the resistance is important to the
manufacturer, they much keep them in a special dry engvironment, just
like flux coated welding rods.

2) If you have carbon composition resistors which have gotten damp,
they can be dryed out by heating them to temps below 100C for several
days. 2 Watters take longer than 1/4 Watters. Don't try to speed this
up by using higher temps.

3) If you solder them when they are "damp" the change in resistance
will be locked in, ie no longer reversible.

Thanks for the info. The four I put on the soldering iron were probably
overheated and won't be salvageable. The rest haven't been exposed to
water or high humidity, generally it's low humidity most of the time
here. So I don't see why they could've changed. I'm thinking that I
might be able to put them inside a ziplock bag with a dessicant and
leave them out in the sun for awhile, and it might help. Can't hurt
much since they're already nearly worthless.

I did this test on a batch of 27k, 2W carbon comp resistors a number
of years ago. They were all high, and most of them were out of
tolerance, this was immediately as purchased from Newark. But they all
came back into tolerance after heating in my home-made oven for about
a week.

But at what temperature? I've got a bunch of old 1- and 2-watt
resistors and I don't think I'll ever use them because I'll never need a
(for example) 27k 2W resistor since it takes a couple hundred volts to
get up to 2W and I don't do tubes anymore.

> -

On Mon, 16 May 2005 18:30:32 -0700 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

Thanks for the info. The four I put on the soldering iron were probably
overheated and won't be salvageable. The rest haven't been exposed to
water or high humidity, generally it's low humidity most of the time
here. So I don't see why they could've changed. I'm thinking that I
might be able to put them inside a ziplock bag with a dessicant and
leave them out in the sun for awhile, and it might help. Can't hurt
much since they're already nearly worthless.

I don't think it takes anything extreme to make this moisture
absorption happen. Try baking them. I think you'll be surprised.

I did this test on a batch of 27k, 2W carbon comp resistors a number
of years ago. They were all high, and most of them were out of
tolerance, this was immediately as purchased from Newark. But they all
came back into tolerance after heating in my home-made oven for about
a week.

But at what temperature? I've got a bunch of old 1- and 2-watt
resistors and I don't think I'll ever use them because I'll never need a
(for example) 27k 2W resistor since it takes a couple hundred volts to
get up to 2W and I don't do tubes anymore.

I wrapped them up in alum foil with a 25W light bulb and stuck them in
a metal wastebasket for a week. As an experiment, I actually took them
out once a day and measured R for each one every day and recorded it.
I suspect the temps were 150-175F. This reduces the RELATIVE humidity
to something really small. A dessicant would do the same thing, but
the heat increases the mobility of the absorbed water, so it's much
more effective.

In a week's time, each resistor was back within tolerance.

As I noted before, however, this will not work with resistors which
have been heated to soldering temps. Allen-Bradley did not explain the
mechanism for this and I don't have any idea what it might be.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

"Jim Adney" <jadney@vwtype3.org> wrote in message
news:updl81581c9s35fhishf8g02lj0ghd2hvi@4ax.com...

On Mon, 16 May 2005 18:30:32 -0700 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

Thanks for the info. The four I put on the soldering iron were
probably
overheated and won't be salvageable. The rest haven't been exposed
to
water or high humidity, generally it's low humidity most of the time
here. So I don't see why they could've changed. I'm thinking that I
might be able to put them inside a ziplock bag with a dessicant and
leave them out in the sun for awhile, and it might help. Can't hurt
much since they're already nearly worthless.

I don't think it takes anything extreme to make this moisture
absorption happen. Try baking them. I think you'll be surprised.

I did this test on a batch of 27k, 2W carbon comp resistors a
number
of years ago. They were all high, and most of them were out of
tolerance, this was immediately as purchased from Newark. But they
all
came back into tolerance after heating in my home-made oven for
about
a week.

But at what temperature? I've got a bunch of old 1- and 2-watt
resistors and I don't think I'll ever use them because I'll never
need a
(for example) 27k 2W resistor since it takes a couple hundred volts
to
get up to 2W and I don't do tubes anymore.

I wrapped them up in alum foil with a 25W light bulb and stuck them in
a metal wastebasket for a week. As an experiment, I actually took them
out once a day and measured R for each one every day and recorded it.
I suspect the temps were 150-175F. This reduces the RELATIVE humidity
to something really small. A dessicant would do the same thing, but
the heat increases the mobility of the absorbed water, so it's much
more effective.

In a week's time, each resistor was back within tolerance.

As I noted before, however, this will not work with resistors which
have been heated to soldering temps. Allen-Bradley did not explain the
mechanism for this and I don't have any idea what it might be.

Well, thanks for the info. It seems that the resistors were made for
tube equipment. The insides of a toob chassis get nice and warm, and
would cook the moisture out of the resistors. Except almost all of the
equipment nowadays is not toob and doesn't get that hot inside.

I found a bag of at least a hundred 56k, 1/2W resistors that are the
same way. I think I'll put the whole bunch into a 'hot box'.
It puzzles me why it should take so long. Maybe the resistors are
coated with something to make them moistureproof, and it's just not
perfect, and lets in the moisture over the years. But when I think
about it, having it take years to get that way, it's really not that bad
having to wait only a week to fix it.

> -

These resistors were manufactured to the military specification
MIL-R-11, which was cancelled in 1997. I do not have access to the
historical document. However, a similar specification for established
reliability carbon-comp resistors is available here:

http://www.dscc.dla.mil/Downloads/Mi...8/mil39008.pdf

The moisture, lifetime, aging, etc. for an RCR07 should be very similar
to an RC07.

On Tue, 17 May 2005 23:30:49 -0700 "Watson A.Name - \"Watt Sun, the
Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

Well, thanks for the info. It seems that the resistors were made for
tube equipment. The insides of a toob chassis get nice and warm, and
would cook the moisture out of the resistors. Except almost all of the
equipment nowadays is not toob and doesn't get that hot inside.

The tube connection is a very good point. I often think about letting
my old tube gear just warm up occasionally to drive off the
accumulated moisture, but I'm still not likely to leave any of them on
for a week. Of course if I used that gear every day everything would
probably be fine.

I found a bag of at least a hundred 56k, 1/2W resistors that are the
same way. I think I'll put the whole bunch into a 'hot box'.
It puzzles me why it should take so long. Maybe the resistors are
coated with something to make them moistureproof, and it's just not
perfect, and lets in the moisture over the years. But when I think
about it, having it take years to get that way, it's really not that bad
having to wait only a week to fix it.

It can be surprising how long it can take to drive off moisture. In
vacuum systems, we will sometimes bake a stainless steel tube to 200C
for several hours in order to produce the best possible vacuum.
Moisture is not the only thing that's being driven off, but it's the
main one, and that's just from a "clean" metal surface.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------