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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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2nd Jul 2022, 5:49 pm | #1 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Brittle Brass Syndrome.
Many of us have rather more than a passing familiarity with the way the stamped 'tuning-fork' contacts in McMurdo B7G/B9A valve-sockets fracture at the point where the two arms of the tuning-fork come together - because the brass has embrittled.
Today I came across another unexpected example of age-degradation in brass; a box of BICC-branded cable-securing straps [which must, admittedly, be at least 40 years old]. The brass was sufficiently embrittled that any attempt to bend the straps caused them to weaken and snap. Cheap brass really doesn't age well.
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2nd Jul 2022, 5:56 pm | #2 |
Nonode
Join Date: Jun 2008
Location: Coningsby, Lincolnshire, UK.
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Re: Brittle Brass Syndrome.
The CRT securing band in my Bush TV22 was just starting to go, it seemed to be where there had been some rubber bits on it, which had since perished and mostly fallen off, I soldered some old bits of used solder braid to it then covered the whole thing in heatshrink, seems ok so far!
Regards Lloyd |
2nd Jul 2022, 6:44 pm | #3 | |
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Re: Brittle Brass Syndrome.
Quote:
Some brasses last better than others, I think due to trace contents having a stabilising influence. David
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3rd Jul 2022, 12:09 pm | #4 |
Nonode
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Re: Brittle Brass Syndrome.
I was reading recently about conditions such as zinc pest, tin pest and bronze disease, which sound similar to this. It seems that impurities during in alloying process and storage conditions can cause problems in later years.
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6th Jul 2022, 1:42 am | #5 |
Dekatron
Join Date: Nov 2009
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Re: Brittle Brass Syndrome.
Without going into too much detail, years ago the water board, while installing a new main, accidentally reconnected an old redundant water pipe that ran across my garden. I woke up the next morning to a great big pond in the garden. When I found the 'new' stop tap that they'd fitted to this old pipe and turned it off, and after letting all the water drain away, I dug down to where the water had come from and was surprised to find two ends of a copper pipe with cleanly cut ends, just butted together. I couldn't work this out at first until I pulled both ends of the pipe up from the ground and cleaned the ends with some sandpaper, whereupon I could see that there was solder on both parts. What had happened was that there would have originally been a brass joiner that had been completely eaten away to the point that it was non-existent, with just the solder left on the two copper pipe ends. I ended up digging most of the pipe up and as I got to the top of the garden, I started to find some of the completely fossilised and brittle remains of brass joints still in place. Several years later I had a leak in the water pipe to the main house and when I dug it up I found that it was another example of a brass joint that had turned to a biscuit type material in the ground, and just crumbled as soon as I touched it.
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6th Jul 2022, 9:10 am | #6 |
Heptode
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Re: Brittle Brass Syndrome.
Philips used three brass bolts to attach the magnets of their AD5201A - AD5201S - AD1255W "Bombardon" woofers (with styrofoam cones). There are multiple accounts of these bolts breaking in time, often destroying the voice coil in the process.
To prevent this from happening to my two AD5201A's, I supported/fixated the magnets in the enclosures I built for them.
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6th Jul 2022, 2:58 pm | #7 |
Dekatron
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Re: Brittle Brass Syndrome.
-Those cable straps seem to be particularly prone to breaking up, but the colour looks odd- as if it was plated with something else, and there's interaction between the base metal and the plating. If it was in a cardboard box i imagine it's been a reservoir for dampness (perhaps residual bleaching agent persists in the cardboard?)
Looking into deterioration of metals is a never ending rabbit hole, but very interesting. Not even gold is immune. As Richard says in Post No.4, impurities are often the enemy, notably lead and mercury insofar as 'pest' is concerned. Dave |
6th Jul 2022, 4:42 pm | #8 |
Nonode
Join Date: Jan 2009
Location: Bristol, UK.
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Re: Brittle Brass Syndrome.
Also, brass 'work hardens' like crazy, to the point where where it will easily crack. If you ever try to put brass sheets through a rolling mill to reduce the thickness you will likely need to anneal it during / after the process.
This is almost entirely due to defects in the crystals 'moving about' under deformation until they get 'jammed together' at which point you notice that its a heck of a lot harder to deform! dc |
6th Jul 2022, 6:28 pm | #9 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
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Re: Brittle Brass Syndrome.
Brass seems to be a 'metal' with issues, in the same sense as some of the old Zinc-alloys [Mazak/Monkey-metal].
I've got here a 1960s Redifon antenna-matcher which was designed/built for a Military contract; the notched 'detent' things for the coil- and capacitor-tap switches were rather massive cast items, sadly implemented in monkey-metal which - by the time I acquired said unit - had deteriorated to the structural integrity of a crumbly Stilton,...
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6th Jul 2022, 9:03 pm | #10 |
Nonode
Join Date: Dec 2012
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Re: Brittle Brass Syndrome.
Regarding the copper water pipe and non-existent brass coupler, my understanding is that in soft water areas (as where I am) and for all buried pipework, only "non de-zincifiable" fittings should be used, by which I understand they mean bronze, though which type of bronze I do not know.
Les. |
6th Jul 2022, 9:23 pm | #11 |
Heptode
Join Date: Sep 2009
Location: Kinver, Staffordshire, UK.
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Re: Brittle Brass Syndrome.
I`ve seen lots of brass valve screening cans split down the sides and the GT style octal valves like 6SN7GT with a split brass shroud around the base.
I`ve been told that this can be caused by the brass item being near a gas appliance for a long time , don't know if this is true ? |
6th Jul 2022, 9:46 pm | #12 |
Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
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Re: Brittle Brass Syndrome.
I believe that splitting can be a result of residual stresses set up when the item was stamped or pressed out. Prevalent in thin brass.
Dave |
8th Jul 2022, 12:21 pm | #13 | |
Dekatron
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Re: Brittle Brass Syndrome.
Quote:
It can't be water or gas since both types of fittings are made from the stuff, surely? Must be damp air or something liberated by rexine or bakelite or similar
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8th Jul 2022, 12:39 pm | #14 |
Dekatron
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Re: Brittle Brass Syndrome.
I had a tape recorder a while back where all the valve holders were rotten and would have needed total replacement. A rotten pinch roller made the machine not worth repairing, but I haven't scrapped it 'yet'!
I also had a radiogram with brass beehive trimmers where the brass had started to deform and split causing one to short out. It seems that this is now regarded as a 'stock fault' with this model. |
8th Jul 2022, 12:49 pm | #15 |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 13,454
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Re: Brittle Brass Syndrome.
Had the same as what's in the link below in one of mine (1st and 2nd photo's):
https://www.antiqueradios.com/forums...lit=meter+case Lawrence. |
8th Jul 2022, 1:07 pm | #16 | |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
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Re: Brittle Brass Syndrome.
Quote:
It was also full of black dust. |
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8th Jul 2022, 2:38 pm | #17 | |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
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Re: Brittle Brass Syndrome.
Quote:
As for the brass, I remember there was a floor that had been over-concreted at some time, but was sinking and sounded hollow. When it was dug up by the building contractor doing the work, it was found that a load of scrap from the original gas works had been used as in-fill under the concrete that had obviously replaced an original rotten wooden floor many decades earlier. There were some massive gas meters that had probably been used to meter the outgoing gas supplies from the site, they'd all gone rotten and had collapsed causing the floor to cave in. I found this so interesting that I salvaged a couple of the movements from these meters - even the glass was still there on one or two. I could be wrong, but I think I may still have the brass remains of a couple of these meter workings somewhere, so if I can find them I'll check them out for brass corrosion and probably post a picture. Last edited by Techman; 8th Jul 2022 at 2:47 pm. |
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8th Jul 2022, 2:47 pm | #18 |
Hexode
Join Date: May 2009
Location: Newcastle, Australia
Posts: 316
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Re: Brittle Brass Syndrome.
Currently working on a CT-212 signal generator.
Brittle brass lugs on the component tag strips. Grrrrrrr. It needs some thought to work around dozens of them. No signs of dampness or excessive heat. Fully sealed case typical of Larkspur equipment. No unusual smells upon opening the case. Just the normal from closed up Larkspur stuff. I have not had any troubles with other Larkspur stuff so the brittle brass problem is not endemic with said radio stuff. Just one of those little tribulations. One of our infamous Australians once said "life wasn't meant to be easy". Cheers all. Robert. |
8th Jul 2022, 10:25 pm | #19 | |
Dekatron
Join Date: Jan 2012
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Re: Brittle Brass Syndrome.
Quote:
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8th Jul 2022, 10:37 pm | #20 |
Nonode
Join Date: Sep 2017
Location: Stockport, Cheshire, UK.
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Re: Brittle Brass Syndrome.
Considering all the noxious by-products produced when making coal gas, it's not surprising some metals would be affected.
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