Value drift over time

C

Cursitor Doom

Guest
Before I junked that RF sig gen I snipped a selection of resistors out of
it just to see how far away from their nominal values they have strayed
over the past ~65 years. I shall report back in due course....



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In article <qbmqra$mh3$3@dont-email.me>, curd@notformail.com says...
Before I junked that RF sig gen I snipped a selection of resistors out of
it just to see how far away from their nominal values they have strayed
over the past ~65 years. I shall report back in due course....
Click to expand...

I can hardly wait! I must have some dating back to before when I was 10
y.o too ;-)

Mike.
 
On Friday, 17 May 2019 21:19:11 UTC+1, Mike Coon wrote:
In article <qbmqra$mh3$3@dont-email.me>, curd@notformail.com says...

Before I junked that RF sig gen I snipped a selection of resistors out of
it just to see how far away from their nominal values they have strayed
over the past ~65 years. I shall report back in due course....

I can hardly wait! I must have some dating back to before when I was 10
y.o too ;-)

Mike.
Click to expand...

I have a few from the 1920s. Don't look a lot like modern Rs. Not sealed either.


NT
 
On Sat, 18 May 2019 15:22:29 +0000, Cursitor Doom wrote:

> The 350VDC Hunts capacitors could easily have been new.

Same type as this: https://tinyurl.com/y6a9ywtz





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On Fri, 17 May 2019 21:19:07 +0100, Mike Coon wrote:

> I can hardly wait!

Then I shall keep you in suspense no longer.

Here's what I found from a random selection of old components I snipped
out. Firstly, pretty much *all* the capacitors were fine. The 350VDC
Hunts capacitors could easily have been new. An Erie plate ceramic of
0.01uF likewise. A Dubilier type SM22 50pf cap, however, had gone up to
62pF. That one was one of the ones used for tuning. The biggest changes
were as expected in the carbon resistors, all of which aged to higher
values like so:

27k became 38.6k

another 27k ----> 29k

100k ----> 107k

10 ----> 10.7

3.3k ----> 4.2k

4.1k ----> 5.2k

15k ----> 20.7k

220k ----> 246k

8.2k ----> 9.9k

400k ----> 509k


These were all marked with a silver tolerance band, so clearly Taylor
back then at least not *that* bothered about accuracy.





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On Saturday, 18 May 2019 16:22:32 UTC+1, Cursitor Doom wrote:
On Fri, 17 May 2019 21:19:07 +0100, Mike Coon wrote:

I can hardly wait!

Then I shall keep you in suspense no longer.

Here's what I found from a random selection of old components I snipped
out. Firstly, pretty much *all* the capacitors were fine. The 350VDC
Hunts capacitors could easily have been new. An Erie plate ceramic of
0.01uF likewise. A Dubilier type SM22 50pf cap, however, had gone up to
62pF. That one was one of the ones used for tuning. The biggest changes
were as expected in the carbon resistors, all of which aged to higher
values like so:

27k became 38.6k

another 27k ----> 29k

100k ----> 107k

10 ----> 10.7

3.3k ----> 4.2k

4.1k ----> 5.2k

15k ----> 20.7k

220k ----> 246k

8.2k ----> 9.9k

400k ----> 509k


These were all marked with a silver tolerance band, so clearly Taylor
back then at least not *that* bothered about accuracy.
Click to expand...

Most Rs in valve kit are far from critical. 5% would have cost them more than 10%. 20% were more common.


NT
 
On Sat, 18 May 2019 09:25:35 -0700, tabbypurr wrote:

Most Rs in valve kit are far from critical. 5% would have cost them more
than 10%. 20% were more common.
Click to expand...

I just put it down to post-war lack of availability but your guess is as
good as mine.
My experience with valves is not that great. I'm really more of the
germanium semiconductor era. ;-)



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In article <qbpi0s$jmv$2@dont-email.me>, curd@notformail.com says...
My experience with valves is not that great. I'm really more of the
germanium semiconductor era. ;-)
Click to expand...

I believe the first computer I got my hands on (just to play with while
I was an apprentice in the factory test bay) was made of those...

Mike.
 
I was in the elctronic surplus bisness from the 60's to the end of the
century. Most people thought that
Allen-Bradleys were the gold standard. One cusomer complained and we
started checking samples.
They were all out of tolerance. A-B's speck sheet specified how to
measure. For a given resistance
range you applied a specified voltage and measured the current.

As an aside: In the 50's I ran across some carbon comp. resistors that
had been modified.
Apparently the person was short of cash or in a hurry. The person took
a CC and a triangular file
and raised the CC to the value neede.

CP
 
On Sat, 18 May 2019 18:20:37 -0700, MOP CAP wrote:

Apparently the person was short of cash or in a hurry. The person took a
CC and a triangular file and raised the CC to the value neede.
Click to expand...

We used to do the same sort of thing with xtals in the days when they
were expensive and hard to come by.



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On 5/19/19 10:01 AM, tabbypurr@gmail.com wrote:
On Sunday, 19 May 2019 12:09:10 UTC+1, Cursitor Doom wrote:
On Sat, 18 May 2019 18:20:37 -0700, MOP CAP wrote:

Apparently the person was short of cash or in a hurry. The person took a
CC and a triangular file and raised the CC to the value neede.

We used to do the same sort of thing with xtals in the days when they
were expensive and hard to come by.
Click to expand...

Except you didn't use a file. You used 600 grit silicon carbide paper
and a piece of glass for a flat surface.

Couldn't do that with my oldest crystal, it's in a valve glass envelope. 5kHz IIRC.
Click to expand...

At the time, the "standard" crystal was the FT-243 which you could
take apart to get to the crystal slab inside.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
 
On Sunday, 19 May 2019 12:09:10 UTC+1, Cursitor Doom wrote:
On Sat, 18 May 2019 18:20:37 -0700, MOP CAP wrote:

Apparently the person was short of cash or in a hurry. The person took a
CC and a triangular file and raised the CC to the value neede.

We used to do the same sort of thing with xtals in the days when they
were expensive and hard to come by.
Click to expand...

Couldn't do that with my oldest crystal, it's in a valve glass envelope. 5kHz IIRC.


NT
 
On Sun, 19 May 2019 10:19:17 -0500, Fox's Mercantile wrote:

Except you didn't use a file. You used 600 grit silicon carbide paper
and a piece of glass for a flat surface.
Click to expand...

Yup, the principle is the same, though. For the final fine 'adjustment'
we'd use Vim, which is a kitchen scouring powder in the UK and many times
less aggressive than 600 grit.




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On Saturday, May 18, 2019 at 8:22:32 AM UTC-7, Cursitor Doom wrote:

Here's what I found from a random selection of old components I snipped
out.
27k became 38.6k

another 27k ----> 29k

100k ----> 107k
Click to expand...

Good to know, but the aging of composition resistors doesn't tell us much
about carbon film resistors (the common low-spec type nowadays) or
metal film (the common high-spec type) and manufacturer coatings
and such are likely to be changing from year to year as well.

Probably, because conductive (metallic or semimetallic) items are positive
valence, oxidation will raise resistance with time, for almost
anything. How much time, is still a mystery (for almost anything
we build today, at any rate).

There's too much chemistry involved to make a really good long-life
high accuracy projection for most real components. Humidity, ozone,
fungus, air pollution... so MANY variables.
 
On Sunday, 19 May 2019 21:12:54 UTC+1, whit3rd wrote:
On Saturday, May 18, 2019 at 8:22:32 AM UTC-7, Cursitor Doom wrote:

Here's what I found from a random selection of old components I snipped
out.
27k became 38.6k

another 27k ----> 29k

100k ----> 107k


Good to know, but the aging of composition resistors doesn't tell us much
about carbon film resistors (the common low-spec type nowadays) or
metal film (the common high-spec type) and manufacturer coatings
and such are likely to be changing from year to year as well.

Probably, because conductive (metallic or semimetallic) items are positive
valence, oxidation will raise resistance with time, for almost
anything. How much time, is still a mystery (for almost anything
we build today, at any rate).

There's too much chemistry involved to make a really good long-life
high accuracy projection for most real components. Humidity, ozone,
fungus, air pollution... so MANY variables.
Click to expand...

You can eliminate all those with glass, vacuum & getter. Then you find one day that the getter is oxidised & the bulb contains hydrogen.


NT
 
On Sun, 19 May 2019 13:24:18 -0700, tabbypurr wrote:

You can eliminate all those with glass, vacuum & getter. Then you find
one day that the getter is oxidised & the bulb contains hydrogen.
Click to expand...

I was under the impression that glass was impermeable even to omnipresent
hydrogen. Or is there a path via where the base pins protrude?



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On 5/19/19 5:45 PM, Cursitor Doom wrote:
I was under the impression that glass was impermeable even to omnipresent
hydrogen. Or is there a path via where the base pins protrude?
Click to expand...

Hydrogen atoms are really really small.
Trying to keep hydrogen in or out is always problematic.


--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com
 
On 20/5/19 10:50 am, Fox's Mercantile wrote:
On 5/19/19 5:45 PM, Cursitor Doom wrote:
I was under the impression that glass was impermeable even to omnipresent
hydrogen. Or is there a path via where the base pins protrude?

Hydrogen atoms are really really small.
Trying to keep hydrogen in or out is always problematic.
Click to expand...

Also, a kilogram of hydrogen at a given pressure takes more space than
any other gas.
 
On Sunday, 19 May 2019 23:45:14 UTC+1, Cursitor Doom wrote:
On Sun, 19 May 2019 13:24:18 -0700, tabbypurr wrote:

You can eliminate all those with glass, vacuum & getter. Then you find
one day that the getter is oxidised & the bulb contains hydrogen.

I was under the impression that glass was impermeable even to omnipresent
hydrogen. Or is there a path via where the base pins protrude?
Click to expand...

Glasslinger did a mass spec analysis to discover that gassy valves contain hydrogen. I don't know whether that permeates through the glass (unlikely since most valves stay hard), leaks in through pin sealing defects or is the result of remaining water vapour reacting with the getter. Either way a getter that could capture it would be a good thing probably.

https://www.youtube.com/watch?v=16vOoF_XUB8


NT
 
In article <rvOdnSbLyqpFZHzBnZ2dnUU7-TmdnZ2d@giganews.com>,
jdangus@att.net says...
Hydrogen atoms are really really small.
Trying to keep hydrogen in or out is always problematic.
Click to expand...

In practice you get molecules on the two-fer principle which are much
bigger. Helium is bad too because then the atoms come at you singly...

Mike.
 
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