PVC wiring in old equipment

[Philips210]

Hello again.

Today, I decided to have a quick look at a Farnell L30A bench power supply that I acquired about ten years ago. It's not in the best condition having been probably stored in damp conditions. The plan was to open it up and give it a good check over. I intend to clean all the pots and switches. Also, I'll probably replace the electrolytic caps.

Now to my concern. What I noticed was a quite strong smell from the PVC wiring similar to those cheap Christmas tree lights from the 1970s. I don't really know if this smell from the PVC is considered normal. The problem is I have an extremely sensitive sense of smell so what I can detect as uncomfortable may not be discernable by the majority of the population. The thing is, not all PVC wiring seems to be the same as I often can't pick up any objectionable odour.
In this Farnell PSU, it is quite smelly even though the wiring looks to be in good condition. The PVC is quite shiny in appearance. I am considering replacing the wiring which will be quite a task.
I had a similar thing with the PVC mains lead on my Philips TVette which reeked.

Also, I have an immaculate Pye 14" CTV with the Philips KT3 MkII chassis and this also gives off a quite nasty smell from the wiring especially as it warms up. I can't seem to clear that problem which is annoying as the chassis looks like new and the set is spotless inside.
I wonder if airborne pollutants could be reacting with the PVC causing it to degrade and become more smelly.

Over the years I've bought many reels of different types of cable and the vast majority don't seem to be a problem. A bargain reel of screened cable from a car boot sale was so bad that I took it to the recycling centre to be rid of the smell. It was a well known maker but the reel was very old new stock. Perhaps it is an age related thing rather than through usage.


Has anyone else noticed this with PVC wiring in some types of equipment?

Regards,
Symon

[Techman]

Originally Posted by Philips210

objectionable odour.

You don't say what this 'odour' smells like, so I'm going to say it - BO!

If it is like a human BO type smell, then I would say that it's perhaps some of the other plastic items within the PSU. I've never noticed any particularly strong and unpleasant smell from PVC wiring, although the green liquid rot is well known, although thankfully not that common in some old house wiring installations. I've got a plastic bucket that I've had for years that started giving off the BO smell and I've also had it from an old washing up bowl and some very old square plastic storage containers when I was at work. These items were all fine for years and then just suddenly started making the store room smell of BO.

[Philips210]

Hello.

I would say the bad smell can be described as plasticy if that makes sense. I don't detect it smelling like BO.
The mains lead also has a similar smell to it. Either it is fairly normal for some types of PVC or it has undergone some kind of degradation. Either way, it's not very pleasant.

Regards,
Symon

[Techman]

Ah, so it's just a 'plastic' type of smell. It could be that I just don't notice it and would probably just call it a 'new' type smell that doesn't bother me too much. However, I remember when the pound shops first started up going back a few years, they always had a certain 'smell' to them, which I would perhaps describe as a 'not so pleasant' plastic gone off type smell. I don't know what changed, but the pound shops haven't had this smell for quite a few years now.

What was an annoying smell from PVC wiring was when I scrapped an old automatic washing machine and remove the wiring loom for all the useful gauges and colours of wire for future use in repairs etc. and it made the whole workshop stink of soap powder scent. I'm still using that wire and it now no longer has that smell, but it must have taken a couple of years or so before it eventually lost it altogether.

[Philips210]

Interesting. Perhaps the PVC can absorb certain airborne chemicals.

Talking of smelly plastics. I purchased a new Bush TV recently and the plastic case has an awful smell so have put it back in its box. I had put it in an out building to hopefully clear the smell but it is no different after three months. It's as if it has been made from low end recycled plastic.
My 2009 Bush TV is absolutely fine as is a slightly younger model that I purchased.

Regards,
Symon

[Lloyd 1985]

I’ve got a Hitachi black and white portable telly that smells like armpits… I thought it just needed cleaning, so stripped it down and gave it a bath, but the smell came back! I also noticed the casing is beginning to go crumbly on the surface.

Regards
Lloyd

[GrimJosef]

I don't have an extremely sensitive sense of smell, so I can't recall ever having been bothered by the smell of PVC insulation. It's plastic and it smells to me of, um, plastic. However I do know that it doesn't just contain PVC (poly-vinyl chloride).

PVC in its natural state isn't very flexible. It's the semi-rigid stuff that waste-water pipes are made from. Slightly confusingly we've now taken to calling it uPVC where the u stands for 'unplasticised'.

The sort of PVC that is used for wire insulation is flexible and that's because it also contains a plasticiser. There are a number of different plasticiser options. I wonder if you can detect the different smells of different plasticisers and that's why PVC sometimes smells objectionable to you and sometimes doesn't ? I'm aware that plasticisers can also alter over time. Certain early types of PVC were prone to losing their flexibility after long periods of running warm/hot. I've always assumed that was due to the plasticiser being lost, or undergoing some sort of chemical change. A particular example is the insulation on the 'hookup' wiring that Radford used in their STA15 and STA25 amplifiers. It's common to find that the last few millimetres of insulation leading up to a hot tag in a valve socket have, over the decades, become completely rigid.

Cheers,

GJ

[alanworland]

I've had a lead light fitted with a long length of PVC cable - I think it smells gorgeous! Over the years it's got dirty/grubby/oily and has been wiped down with petrol or paraffin soaked rags but the smell is still as pungent as the day it was fitted and shows no signs of deterioration.
Everytime I use it I get a (gorgeous) waft!

Alan

[Philips210]

Yes, certain models of TVs etc can have a fair old pong. When I used to do TV repairs you became familiar with various makes by the smell they gave off when on and in some cases when off.
I have an old JVC 3V16 VCR and that smells terrible. I believe it may be due to the PCBs, possibly what they were cleaned with after manufacture coupled with moisture ingress to the phenolic material. In my case, I notice these smells very easily. It's hard to explain but it can make everyday life unpleasant which adds to the anxiety. Perhaps I ought to try and get an appointment with an ear/nose/throat specialist and get tested for hyperosmia.

Regards,
Symon

[Philips210]

Originally Posted by GrimJosef

There are a number of different plasticiser options. I wonder if you can detect the different smells of different plasticisers and that's why PVC sometimes smells objectionable to you and sometimes doesn't ? I'm aware that plasticisers can also alter over time.
Cheers,

GJ

That's a good point GJ and would explain why most PVC insulation is fine. I can't say if it the PVC would have originally been like it or has undergone change over the years.

Regards,
Symon

[Philips210]

Originally Posted by alanworland

I've had a lead light fitted with a long length of PVC cable - I think it smells gorgeous! Over the years it's got dirty/grubby/oily and has been wiped down with petrol or paraffin soaked rags but the smell is still as pungent as the day it was fitted and shows no signs of deterioration.
Everytime I use it I get a (gorgeous) waft!

Alan

It's funny you say that Alan. I remember the smell of the Christmas tree lights wiring as a young child. To me, I liked it at the time but nowadays wouldn't want to smell it for too long. Phenolic substrates used to smell great but have found I don't like it now.

Regards,
Symon

[Philips210]

I just remembered back in about 1977 my parents bought me a radio kit from Radio Exchange (Bedford). I always remember the pungent smell from the PVC sleeving supplied with the kit. As GJ points out, I think it is due to the type of plasticiser.

Regards,
Symon

[The Philpott]

Changes to the sense of smell can be caused by covid vaccination, and also by contracting the virus. (I experienced both)

I know that PVC wiring insulation emits a smell after contact with bare hands- which is then attractive to rodents. This is why i always wear gloves when tackling wiring in outbuildings or lofts.

Dave

[emeritus]

PVC does slowly give off a chlorine compound vapour that is harmless in an unsealed environment that allows it to escape. However, in hermetically-sealed enclosures, the concentration can become strong enough to attack certain other plastics. This is why PTFE insulated wire is used for sealed military /avionics equipment. At Plessey we were given an example of the consequences of failing to follow this practice. When a hermetically-sealed module had been repaired, the technician had used ordinary PVC wire instead of the specified PTFE, and when it was subsequently returned as faulty a second time, it was found that the fumes from the PVC insulation had dissolved the polystyrene capacitors.

[Restoration73]

At high temperatures (e.g. during soldering) PTFE also gives off harmful fumes.
Ensure a well ventilated area. You have been warned !

[QQVO6/40]

Greetings all.

Emeritus is spot on with his post.
Please take note anyone working on Clansman and Larkspur radio equipment or anything with hermetic sealing.
It does not take long for the PVC wiring in these locations to wreak it's havoc.
Out in the open where it can breathe in my experience is fine.
Locked in a box that is not open to fresh air: NAH Forget it.

Sorry for labouring the point but I have seen really good bits of gear destroyed by this simple mistake.

I'll get ma hat ma coat on the way out the door.

Cheers all.
Robert, VK2BNM.

[Nickthedentist]

No sign of the green gunge which often afflicts early (1960s?) PVC house wiring?

[Lucien Nunes]

'Green goo' which is sometimes found in electrical installation cables forms when the exuded phthalate plasticiser comes into contact with bare copper. Equipment wire usually has tinned copper conductors, which I would expect to prevent the green color forming. I believe the main problem that causes the plasticiser loss was the use of an anti-oxidant to raise the temperature rating of the cable, with unexpected side effects. In the electrical installation context, the problem of PVC vs. polystyrene is well known from the insulation damage that has occurred through contact with PS thermal insulation.

Plasticiser oozing out in liquid form is quite drastic, as it represents a high percentage loss of mass and concentration in the PVC compund, likely to have an immediate impact on the remaining material. OTOH, with the nose being a very sensitive organ, even a tiny fraction of the mass lost as vapour over years or decades can result in an easily detectable odour. I have a 50-year old PVC toy from when I was a baby, which has always had the same stable, mild, recognisable smell of plasticiser but shows no loss of suppleness, smoothness or strength.

As with rubber insulation where there are many variables governing the stability and ultimate degradation pathway of the material, it's probably hard to predict exactly how a particular specimen of plasticised PVC will fare in conservation 50 or 100 years hence, although someone with a good nose and polymer science knowledge to back it up could probably take a good guess. Thermal conditions and exposure to contaminants including volatiles from other components in the same assembly, clearly can play a part as well as the original composition of the specimen.

Off-gassing of polymers is a known problem in the museum world, where knock-on damage can occur even without the completely sealed environment of the high-spec electronics enclosures described above. For example, the London Transport Museum have a complex task managing the off-gassing of upholstery foam used in seats, which would have to be permanently damaged to remove the offending foam but which pose a risk of damage to other materials.

I'll take the opportunity to mention some interesting specimens of PVC wiring that I come across that I believe to be pre-WW2. I did previously ask about peoples' experience of very early PVC insulation but found little conclusive evidence of its use in electronics in 1937-8. However, the wiring looms of Compton Melotone electrostatic tone generators from these years appear to be PVC-insulated and are typically in excellent condition today. Along with many early examples of high-quality PVC equipment wire, the PVC tends to be quite firm, resistant to soldering heat and generally well-behaved. I wonder whether there was a general change in plasticiser in cheaper material when it became commoditised, and stability was sacrificed for economy.

[Tim]

Ahh, one of my favourite smells( along with fresh tarmac/creosote and new mown grass) is that lovely PVC smell you get from a new beach ball.

[knobtwiddler]

My Nak and Sony cassette decks were made for the domestic Japanese market (100v) and both have differing but distinctive smells, that only make themselves known once warmed up. I've never really thought about the origin of it in terms of components, but it is pungent and not unpleasant.

Edit - because they emit the smell when warm, the little thought i have given it made me think it was connected with PCB material and flux, but I may be wrong