Carbon Comp: Aging Causes Out Of Tol?

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%.

Thanks.
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"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%.

Thanks.

Do you know their history? Maybe they were out of tolerence at time of
manufacture.

I always heard that carbons change value with humidity. I have many unused
Allen Bradley 5% 1/2W carbons which I took from new stock in the early 70's, and
checking a few of the BROWN-third-band ones at random show all within tolerence.

"Michael" <NoSpan@att.net> wrote in message
news:42874D32.71868CB0@att.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%.

Thanks.


Do you know their history? Maybe they were out of tolerence at time
of
manufacture.

I don't know their history, only that they are still in the tape that
they were in when they came from the factory, with the factory
designation stamped on the tape, so they should be NOS. I've seen tapes
from some place that have various components customized for a stuffing
machine, and this is not one of those.

One would think that it would not be possible for these to be out of tol
when they come from the mfgr, unless there was a major malfunction in
their testing equipment. However, I've heard of such things as
warehouses catching on fire, or goods being shipped in a ship hold next
to a steam boiler, where in either case the goods were exposed to
excessive temperatures. This could have caused some change. But my
experience is that higher temperaturss cause resistors to become lower
resistance.

I always heard that carbons change value with humidity. I have many
unused
Allen Bradley 5% 1/2W carbons which I took from new stock in the early
70's, and
checking a few of the BROWN-third-band ones at random show all within
tolerence.

I checked another bag of loose carbon comp resistors, 6.8 ohm, 1/4W, 5%.
All of them are also greater than 5% out of tolerance, and that is
taking into account the 0.4 ohm resistance of the test leads.

On Sun, 15 May 2005 07:50:42 -0700, the renowned "Watson A.Name -
\"Watt Sun, the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:

"Michael" <NoSpan@att.net> wrote in message
news:42874D32.71868CB0@att.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%.

Thanks.


Do you know their history? Maybe they were out of tolerence at time
of
manufacture.


I don't know their history, only that they are still in the tape that
they were in when they came from the factory, with the factory
designation stamped on the tape, so they should be NOS. I've seen tapes
from some place that have various components customized for a stuffing
machine, and this is not one of those.

One would think that it would not be possible for these to be out of tol
when they come from the mfgr, unless there was a major malfunction in
their testing equipment. However, I've heard of such things as
warehouses catching on fire, or goods being shipped in a ship hold next
to a steam boiler, where in either case the goods were exposed to
excessive temperatures. This could have caused some change. But my
experience is that higher temperaturss cause resistors to become lower
resistance.

I always heard that carbons change value with humidity. I have many
unused
Allen Bradley 5% 1/2W carbons which I took from new stock in the early
70's, and
checking a few of the BROWN-third-band ones at random show all within
tolerence.

I checked another bag of loose carbon comp resistors, 6.8 ohm, 1/4W, 5%.
All of them are also greater than 5% out of tolerance, and that is
taking into account the 0.4 ohm resistance of the test leads.

Maybe your meter needs a new battery? ;-) Long ago I bought a Micronta
DVM for the guys to use in testing product (to replace one they
killed, and needed *now*). I was surprised to find how nonlinear it
was-- a good fraction of 1%, though still within specs-- it had some
crap ASIC that was nowhere near the virtually perfect performance of
the Intersil inspired chips.

There were also problems about 20-30 years ago, well covered in the
trade rags at the time, about out-of-tolerance mil-spec resistors.
Don't recall whether they were film or composition types. It was a bit
of a scandal-- when you pay 20 or 50 times the price, you don't
necessarily expect them to be worse than the standard commercial types
(though it makes sense that problems could crop up due to low-volme
special production arrangements).


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

Yup, carbon composition was notoriously unstable. The phenolic casing was not
hermetic and allowed moisture in and out. About the only way they were better
than carbon film was in power surge rating. A 1 watt could take 5 watts of
overload for a split second without more damage than a small change in value.
Carbon films would flash and flameout.

Also, carbon comps have lower self inductance than carbon film, so you'll
sometimes see them still used in RF power circuits. Sometimes with coils wound
about the body, too.

I remember when Ohmite announced years ago they were ceasing production on their
comps and so many engineers wailed 'No!'. Ohmite relented, but did get to raise
prices.

You may be able to sell them on ebay to people who need replacement parts for
their old gear.


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%.

Thanks.

On Sun, 15 May 2005 16:08:55 GMT, the renowned
_crusty@ourwonderful.sytes.net wrote:

Yup, carbon composition was notoriously unstable. The phenolic casing was not
hermetic and allowed moisture in and out. About the only way they were better
than carbon film was in power surge rating. A 1 watt could take 5 watts of
overload for a split second without more damage than a small change in value.
Carbon films would flash and flameout.

Also, carbon comps have lower self inductance than carbon film, so you'll
sometimes see them still used in RF power circuits. Sometimes with coils wound
about the body, too.

I remember when Ohmite announced years ago they were ceasing production on their
comps and so many engineers wailed 'No!'. Ohmite relented, but did get to raise
prices.

You may be able to sell them on ebay to people who need replacement parts for
their old gear.

A client says he switched to them for one application because the
extra noise helped an oscillator start reliably. I'm not sure I
believe it was the factor (the parts he got looked just like film
parts to me, with the telltale bulge of crimped endcaps over a tubular
body) but maybe it got the semiconductor maker ********* out of a
possibly litigious bind by killing enough time for another wafer run
to get out.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

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


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"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...)

"Spehro Pefhany" <speffSNIP@interlogDOTyou.knowwhat> wrote in message
news:qtoe815rr9q12qlnntk9co21db4gtc0t1d@4ax.com...

On Sun, 15 May 2005 07:50:42 -0700, the renowned "Watson A.Name -
\"Watt Sun, the Dark Remover\"" <NOSPAM@dslextreme.com> wrote:


"Michael" <NoSpan@att.net> wrote in message
news:42874D32.71868CB0@att.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%.

Thanks.


Do you know their history? Maybe they were out of tolerence at
time
of
manufacture.


I don't know their history, only that they are still in the tape that
they were in when they came from the factory, with the factory
designation stamped on the tape, so they should be NOS. I've seen
tapes
from some place that have various components customized for a
stuffing
machine, and this is not one of those.

One would think that it would not be possible for these to be out of
tol
when they come from the mfgr, unless there was a major malfunction in
their testing equipment. However, I've heard of such things as
warehouses catching on fire, or goods being shipped in a ship hold
next
to a steam boiler, where in either case the goods were exposed to
excessive temperatures. This could have caused some change. But my
experience is that higher temperaturss cause resistors to become
lower
resistance.

I always heard that carbons change value with humidity. I have
many
unused
Allen Bradley 5% 1/2W carbons which I took from new stock in the
early
70's, and
checking a few of the BROWN-third-band ones at random show all
within
tolerence.

I checked another bag of loose carbon comp resistors, 6.8 ohm, 1/4W,
5%.
All of them are also greater than 5% out of tolerance, and that is
taking into account the 0.4 ohm resistance of the test leads.

Maybe your meter needs a new battery? ;-) Long ago I bought a Micronta
DVM for the guys to use in testing product (to replace one they
killed, and needed *now*). I was surprised to find how nonlinear it
was-- a good fraction of 1%, though still within specs-- it had some
crap ASIC that was nowhere near the virtually perfect performance of
the Intersil inspired chips.

I rechecked a bunch of them with a bench DMM and they're all the same:
5% or more higher than marked. The 6.8 ohms measure 7.2 or more. The
910s measure close to 1k. Usually I measure a 1% precision resistor on
the same range, just to make sure things are working right.

Someone should take the initiative and include a precision resistor in
each DMM, with the two leads sticking out the front. Something similar
to the calibration source that I've seen on the front of decent
o'scopes. A 1% resistor costs only a penny or two.

There were also problems about 20-30 years ago, well covered in the
trade rags at the time, about out-of-tolerance mil-spec resistors.
Don't recall whether they were film or composition types. It was a bit
of a scandal-- when you pay 20 or 50 times the price, you don't
necessarily expect them to be worse than the standard commercial types
(though it makes sense that problems could crop up due to low-volme
special production arrangements).

Reminds me of the 3 foot cat5 patch cords we ordered. Came bagged 50 to
a bag. Supposed to be tested to cat5 specs. I reached in and pulled
out a half dozen with one end bare, no connector. Well, if they really
_were_ tested, they would've caught that 'minor' problem. :-P

Best regards,
Spehro Pefhany
--

"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. :-(

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.

> --