I am prompted to write this entry to the forum due to a dangerous power lead I recently found on a H.M.V. 68-55 radio.

After securing the ferrite antenna and restringing the dial/tuning mechanism, I noticed that the power plug had some green goo coming out of the plug inbetween the pins and the plastic.
I cut off the old plug and attempted to strip back the lead to attach the new mains plug.
The rubber insulation would not separate and all three wires had become as one. I now knew that I would have to replace the whole lead.

When I went to remove the other end, moving the wires caused the insulating rubber to crack and expose the bare wires.
Note. This lead is plastic covered rubber insulated wire, a replacement for the earlier Cotton covered rubber type.

Having seen the condition of the wires inside, I am amazed that there was not a short where the lead passed through the grommet at that back of the chassis. I have been cautious of earlier power leads, but will now inspect more carefully all leads. Not just the pre-plastic covered types.

P.S. The dial stringing on this model is diabolical. Even with the instructions. The previous repairer had given up on this one. I rate it right up there with the two string Tasma.

Wayne.

Mains cable with rubber insulation and (usually) grey PVC jacket is very common in gear from the 50s and 60s. I've seen a lot of it.

My AWA and my Kriesler TV both had that type of cable - first thing I replaced!

Wise to alert others to the risk Wayne.

Most of the TVs and radiogram I have from the 50s and early 60s are all like that. If I find one thats good I'm amazed. I replace all the leads ,I dont risk it . I'm not experienced enough to fix the unit if it was to damage it.
It might blow a transformer etc etc That old fuse system would be lucky to stop chassis damage I imagine.
Funny thing is yesterday the kids bumped a fruit bowl off the top of my 1957 fridge and it stopped working.
So I looked at what had happen and the fruit bowl had it hit the lead on its way down the back of the fridge and shorted it out ,Because of that same rotting and melting lead you described.
So lucky it happened as I forgot to replace the fridge lead.,,all done now though.

I generally replace leads on any radio I restore, regardless of age though in the past the main reason was aesthetics as much as safety, especially if the original appeared okay.

Any radio that came with a figure-8 flex was automatically replaced, no matter what as single-insulated cords are just wrong in my opinion. It is amazing that compact cassette players came with them right up until their demise. By the time the now familiar radio-compact disc players came into vogue the manufacturers had shifted to double-insulated flexes.

The first PVC flexes were a complex beast. They still contained three cores that were insulated with VIR rubber and to make the flex circular it was packed with hemp string. PVC coated cores followed and this is where the problem with the green ooze entered the fray. There are a lot of tales on the Internet about what the ooze is and what causes it. It is generally accepted that it is the result of a reaction between the poly-vinyl chloride that the insulation is made of and the copper conductors. The same happens to the TPS wiring in buildings and also to telephone wiring - all due to the same cause. At times someone will say it is due to rat poison mixed in with the insulation, however this is urban myth. There was never a poison as such mixed in with the plastic. It was a deterrent, simply to stop rats eating the insulation and it was only ever included in the outer sheath of TPS cable - not the insulation on the cores themselves or on flexible cords.

There is also a debate about whether the ooze is toxic or not. I am not sure myself but have always tried to err on the side of caution and wash off any that ended up on my fingers. Unfortunately in the electrical trade it isn't really possible not to confront the green ooze every now and then. I'm still alive after 25 years in the job so whatever I have done, it has been the right move. Soap and warm water.

Well , while we are on this topic perhaps you guys could answer this question for me.
I always replace all my main leads and its the first thing I do, But many TVs use a thin core lead ,Im guessing at 7mm? So I replace the all with the 3 core with a heavier lead and at a guess I would say its 9,5 or 10
Will this cause any issues???
I did it because some TVs really have a thin crappy mains lead.
Pete

The average size for an appliance like a telly or computer is 0.75mm², and this is ample for a radio. It'll carry about 4, maybe 5 amps with no trouble.

Hmmm ok thanks Brad.
Timbers I know but electronics I'm still lost in the long grass.
Thanks Pete

You'd want the power cord to be able to pass enough current to trip the house wiring circuit breaker, if a short inside the radio or TV ever happens. In the USA, 18 AWG is the minimum size to be plugged into 15 and 20 amp house circuits, which are wired with AWG 14 and 12 respectively. Otherwise you could run an electric clock (about 7 watts) on 24 AWG wire, but that size wire (thinner than the 18 gauge) would not pass enough current to trip the breaker, but it would turn into a fire starting electric heater...

I've seen power cords with that green goo. Cords that date back to the 50's and early 60's. Don't know what that goo is, but odds are that it causes cancer... Seen other plastic power cords that got stiff and would break apart if you try bending them.

Wa2ise
Thats what I thought was going on in the old TVs particularly in the 3 in 1 combo units . I thought that the wire was too thin and was getting hot and melting because it couldn't handle the load and this is why I just started replace all my mains with a heavier gauge.

You're lucky over there in the states as there is a Abundance of old stuff!! TVs, radios , parts, old collectables etc, etc ,
I have family in the USA they use to run Taronga Zoo here in Sydney and now they live a place called Birmingham.
One day I will go vistit the states, I have been to many countries around the world but never the states.
Pete

Pete, I suppose you'd find the USA fairly similar to Australia, as I did finding Australia similar to the USA back when I took a holiday in 1986. Oh, things like driving on the other side of the road, and Americans not having accents (we don't have culture either) .

Our tour guide said that Aussie kids call this place the "American Embassy":

Don't bring a digitally tuned AM MW radio, our stations are spaced every 10kHz, not 9kHz. And our AM MW band goes up to 1700kHz.

Haha,
Not much culture here in oz apart from Yorgurt!
The place has change since 1986.You would not recognise it now and boy did it get expensive!
All the best Pete

Seen other plastic power cords that got stiff and would break apart if you try bending them.

I have two Hammond organs, one from the 1950s the other from 1960s, which had exactly that issue. Both original power cables snapped like twigs.

The most common nickname here for McDonalds is Maccas followed by The Golden Arches but there's a few derogatory names too, such as Rotten Ronnie's.

One of the first things to check when assessing a radio etc. is all of the wiring. I am constantly replacing mains cables. One reason is to earth the metal chassis, the other is always their condition & I have had a couple where it is amazing, and I marvel at how someone unplugged it & lived, or it had not started a fire.

They do not escape the place with out I run them through the Tag & Test routine. I did get a 20 metre caravan cable recently to test and found no continuity in the earth wire (scary): Not much help in a crisis. Obviously that did not get back into service.

Note with 245 VAC here and 120 VAC, or so there (USA), we are moving much less current for the same wattage.

Marc

Many privately owned caravan parks require campers to test/tag their van lead before arrival at the park and the park staff do check to see if a valid tag is applied and there's been stories about refusal of entry and surrender of booking fees for those with non-compliant leads. I am assuming that this also applies to tent campers who occupy powered sites.

When I go camping there is no regime in place to audit this though as the places I stay are usually run by the NSW National Parks and Wildlife Service, whose camping grounds are mostly run with the honesty box system for payment of camping fees and have no staff apart from those who clean the ablution blocks and take away the rubbish.

In my time in camping grounds, public or private, I have seen a lot of van leads and other flexible cords connected to the mains and to generators which clearly aren't safe to use. Such leads include the yellow/orange leads that Bunnings sell which have been illegally fitted with a 15 amp socket. These leads are either 0.75mm² or 1mm² and simply will not handle a 15 amp load in anything but blizzard conditions. The minimum required size is 2.5mm² and any lead fitted with a 15 amp socket must also be fitted with a 15 amp plug top.

These cheap leads also come originally fitted with plug tops that contain crimped connections inside and these fail with monotonous regularity. Being used to power a caravan with lights, GPOs, a bar heater or air conditioner and even an electric stovette, some people are just asking for trouble. If you are camping in a tent and only have a camp fridge and some lighting to run, these leads would be adequate.