UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > Hints, Tips and Solutions (Do NOT post requests for help here)

Notices

Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

Closed Thread
 
Thread Tools
Old 16th Aug 2005, 8:28 pm   #41
stephanie
Hexode
 
stephanie's Avatar
 
Join Date: Jul 2005
Location: New Bern, North Carolina, USA
Posts: 346
Talking Re: Vintage radio safety

Quote:
Originally Posted by Nickthedentist
Lucky I'd put a 3A fuse in the plug (it had the ubiquitous 13A original one when I plucked it off the skip
Wow. You mean the previous owners actually forgot to unscrew the 50 pence plug from the mains flex, before they tossed the TV set out?
__________________
Stephanie Weil
New Bern, North Carolina, USA
stephanie is offline  
Old 16th Aug 2005, 8:32 pm   #42
Nickthedentist
Dekatron
 
Nickthedentist's Avatar
 
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 15,632
Default Re: Vintage radio safety

Quote:
Originally Posted by stephanie
Wow. You mean the previous owners actually forgot to unscrew the 50 pence plug from the mains flex, before they tossed the TV set out?
You may well laugh, but there was an annoying gang of old men who used go to all the jumble sales in Wimbledon at the time I found the telly (late 1980s) buying up broken electrical gear, just to get cheap 13A plugs. If it didn't have a plug, they wouldn't touch it
Nickthedentist is offline  
Old 16th Aug 2005, 11:53 pm   #43
Biggles
Rest in Peace
 
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 2,234
Default Re: Vintage radio safety

Hi all, talking about the dangers encountered so far, has anyone seen that old article in the "1934 Short wave radio manual" about heating your home (or rather yourself) by using a high power RF transmitter in the cellar to induce heat into your body? Doesn't bear thinking about! Apologies if this is straying a bit off topic.

Biggles.
Biggles is offline  
Old 17th Aug 2005, 3:12 pm   #44
stephanie
Hexode
 
stephanie's Avatar
 
Join Date: Jul 2005
Location: New Bern, North Carolina, USA
Posts: 346
Wink Re: Vintage radio safety

Quote:
Originally Posted by Nickthedentist
You may well laugh, but there was an annoying gang of old men who used go to all the jumble sales in Wimbledon at the time I found the telly (late 1980s) buying up broken electrical gear, just to get cheap 13A plugs. If it didn't have a plug, they wouldn't touch it
OK. Going off topic for a second. That doesn't make sense.

I can understand skip-diving to cut the re-wireable plugs off discarded appliances. I might do that if I were on some sort of budget also.

But BUYING broken electrical gear just to get the plug? A 13-amp plug costs anywhere from a quid-and-change to two pounds for a good MK-brand type; to a few pence for those cheap-tat imported jobbies (at least what I've seen on the web).

Even a broken TV set would cost more than a few pence, no?
__________________
Stephanie Weil
New Bern, North Carolina, USA
stephanie is offline  
Old 17th Aug 2005, 4:04 pm   #45
evingar
Octode
 
evingar's Avatar
 
Join Date: Oct 2003
Location: Newbury, Berkshire, UK.
Posts: 1,757
Default Re: Vintage radio safety

Quote:
Originally Posted by stephanie
OK. Going off topic for a second. That doesn't make sense.

I can understand skip-diving to cut the re-wireable plugs off discarded appliances. I might do that if I were on some sort of budget also.

But BUYING broken electrical gear just to get the plug? A 13-amp plug costs anywhere from a quid-and-change to two pounds for a good MK-brand type; to a few pence for those cheap-tat imported jobbies (at least what I've seen on the web).

Even a broken TV set would cost more than a few pence, no?

Well my max for old busted TV's at jumble sales was always about a shilling; I received 2 bob a week pocket money (excluding kindly donation from furry old aunts etc, the money was never worth having to kiss the moustache though I must confess though, I have no idea of the price of mains plugs back in those days
__________________
Chris
evingar is offline  
Old 18th Aug 2005, 8:36 am   #46
ppppenguin
Banned
 
ppppenguin's Avatar
 
Join Date: Dec 2003
Location: North London, UK.
Posts: 6,168
Default Re: Vintage radio safety

I've just acquired a load of issues of "Which?" from the 1960s and 70s. In the January 1971 issue, the cover shows a noose made of cloth covered flex with the text:


In November 1970, 6 irons failed the British Standard safety tests
In December 1970 3 toasters failed
This month 3 tape recorders failed
At last they're doing something about it.

According to the editorial column, there was no law against selling unsafe products at that time and buyers were cautioned to look for the BEAB label.

So much for equipment being safer 30 or 40 years ago.

These old issues of Which? are an interesting vintage wireless resource too. Loads of reviews of radios, cassette recorders, TVs etc.
ppppenguin is offline  
Old 18th Aug 2005, 12:30 pm   #47
Stewart
Hexode
 
Stewart's Avatar
 
Join Date: Jul 2003
Location: N.E. Surrey, UK.
Posts: 361
Default Re: Vintage radio safety

Indeed I too have been reading through a newly aquired set of Which? magazines from this period - and they do make quite horrifying reading.

It seems no type or class of product was exempt from truely dreadful safety blunders - washing machines whose panels become live if they get wet, live case screws on record players, no flex grip on vacuum cleaners, electric blankets that can set themselves on fire, new cars with brake parts not fitted - the list goes on and on. It's not just cheapo fly by night companies that were responsible - some very well known and respected makes who should have known better come out pretty badly too! (take a bow Philips)

The idea that old equipment was safer just doesn't add up to me. Better built and longer lasting I can accept!

As ppppenguin says these old magazines are a great resource for vintage reviews - and bring the memories flooding back of old cars and equipment. Well worth looking out for at boot sales etc.
Stewart
Stewart is offline  
Old 7th Nov 2005, 7:59 pm   #48
zak
Banned
 
Join Date: Feb 2005
Location: Monmouthshire,on South Wales border
Posts: 85
Default Re: Vintage radio safety

Quote:
Originally Posted by Gordon
Just to lighten things and amuse you, the following illustrations appeared in 'Everything Within' - A Library of Information for the Home (now long out of copyright). We've come a long way since the old dc mains days.
Gordon.
This reminds me when we used to charge accumulators for a bookmaker (betting shop) to check polarity of the mains all you need is the bare ends of the flex and a glass of water,dunk the wire into the water and the one with the most bubbles is the negative (hydrogen).
zak is offline  
Old 30th Aug 2007, 12:21 am   #49
Chris55000
Octode
 
Join Date: Aug 2007
Location: Walsall Wood, Aldridge, Walsall, UK.
Posts: 1,712
Default Re: Vintage radio safety

Hi!

In my experience with vintage radios the worst horror, not so far mentioned on this thread, has to be "line cord".

This dreadful stuff consisted of a very fine, and very long nichrome element
as one of its leads, sold as "x ohms per foot", and makers of "midget" sets (Pilot was fond of this stuff) used it instead of droppers or barretters for the series heater circuits. The idea was simple in theory - you calculated length required by dividing the total series resistance needed by the "ohms per foot" specified to give the length in feet needed - trouble is our 200-250V supplies needed yards of the wretched stuff, and fires were not unknown because unwitting householders tried to shorten the "long wire from the set." The other lead was invariably vulcanised rubber, used for the neutral connection.

I would strongly advise anyone not to attempt to try and get a set working with this stuff under any circumstances! Inevitably there's no room in the cabinet for any type of dropping component, so the only safe way of *using*
a set of this type is either a specially-made or several transformers to give the heater-chain voltage, and you'd need 4-way mains-cable!

Apart from the fact that line cord invariably crumbled to dust with heat and age, you had to use special "three-way" line cord in order to get enough HT in UK sets which needed 170V at least as a rule, which meant only single-pole on/off switching was possible, another safety hazard.

The only safe way of dealing with a "line-cord" set is to restore it as a display item only.

Mains transformers:-

In my experience I has always found sets as far back as 1952 when minature valves started to be used to have perfectly safe transformers, assuming of course these were the "isolated type" with a HT half-wave or full wave winding, not just a heater transformer! As long as the mains switch and cable in still safe there should be no problem, but one all too common practice was to knot mains leads at the chassis entry point as proper clamps were very very rare in those days! The dangers of this were obvious - the lead would inevitably harden and crack at the knot resunting in a blue flash, bang and a black sooty inlet hole!

Transformers usually remain safe if they're not overheated due to electrolytic failures, leaky anode-to-grid couplers or shorts on dial lights! Once wax or other impregnation has stared to ooze from a mains transformer, *it is no longer safe* even if it is still running the set apparently normally.

Dropping resistors:- If the cement coating has started to flake off a heater dropper in the AC/DC type set exposing the elements, again the set should be considered no longer safe to test or attempt to use.

Aerial sockets - Before ferrite rods were introduced in the late 50s, most receivers needed external aerials with a two-pin Aerial/earth socket panel, and unless the set is *known* to have a double-wound HT transformer - don't guess! - use a series capacitor of 4700p max of the 250V Class Y type in series with each terminal, and a 2M2 VR37 resistor across the AE/E terminals to prevent static build-up, and one 4M7 VR37 between the E terminal and chassis/HT-.

Finally I mentioned earlier "barretters" - these glorified light-bulb-like devices consisted of a long tungsten filament in a glass bulb filled with hydrogen gas, and they had a marked PTC characteristic which rendered a mains voltage-tapping panel unnecessary. The problem with 'em is that they were fragile, any bump or dropping the set invariably fractured the filament! More to the point, they're totally extinct today - again, a set using one probably wouldn't have room for anything else!

"Capacitor droppers" - *DON'T!!!* I don't believe there's any type of paper/polyester capacitor on the market that will withstand a 150mA-250mA sustained current flow to run heaters in an old radio.

Again, I would agree with other chap's postings that it isn't safe to use a PAT tester on an old radio - you *can't* use one on a "universal set" and the winding insulation (primary to core) of even isolated transformers may not withstand the test voltage.

HT battery replacement for All-Dry sets - the Kit Radio Company's product is really the only feasable and safe way to do it if you want to make the set truly "portable". Whilst you can try stringing 10 PP3s in series, those from car-boot sales may not last very long, even with only 10mA drain. *Don't* try and make one with Alkaline or NiCd or NiMH cells - the short circuit current from even the PP3 size is tremendous and accidental shorts from untidy workmanship could easily cause a dangerous explosion that could put your eyes at risk! It is safe to use one single "D" size alkaline cell in a proper holder
for filament/LT supplies.

Grub screws - many receivers used these for securing their knobs with a beeswax type of stuff to insulate them from the user. I think you can still get
beeswax, but don't try candle grease - it just makes a mess everywhere! Later sets used push-on knobs - this was a BS415 revision at some tiime in the 50s.

Chris Williams
Chris55000 is offline  
Old 30th Aug 2007, 6:40 am   #50
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,485
Default Re: Vintage radio safety

Crikey!

Speaking as someone who collects and restores all kinds of midget live chassis radios (i think I only own one radio with a mains transformer!), I would take you to task regarding your comments made.

There is nothing unsafe regarding the use of line cord as a dropper, providing common sense is used, checking for faulty insulation, and stiffness, usually if the cable has been bundled up tight then the cable will have suffered.

Most Midget radios using American type valves are quite happy running on 110v - indeed I know of many collectors, and professionals that do this as a matter of course, during restoration.

Capacitive droppers, I dont use them personally, but there are large numbers of people that do use them - failure usually takes out a heater chain. I cant really see a safety issue with this.

Barreters? - I can only assume that you have not seen one, otherwise you would not have made the sweeping statement about a lack of room to substitute one for something else - they are normally about the size of an octal rectifier - a simple matter to make a plug in dropper resistor to go in its place, and it will produce a similar amount of heat....

Series chains of batteries, Yes, the KRC unit is a good idea, and a more powerful generator of RF hash you couldnt wish for, but it is a way of running battery sets.

I would doubt anyone would be buying 10 NiMH cells to chain together - the cost would put most people off anyway, collectors have been doing this for years, and there are individuals that are doing this on a commercial basis, I have not heard of anyone setting fire to , or blowing up a battery set due to dodgy batteries.....

Perhaps this redresses the balance here a little - Common Sense - its been protecting mankind since the dawn of time!

Cheers
Sean
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline  
Old 30th Aug 2007, 7:17 am   #51
Mike Phelan
Dekatron
 
Mike Phelan's Avatar
 
Join Date: Nov 2003
Location: Near Leeds, West Yorkshire, UK
Posts: 4,436
Default Re: Vintage radio safety

More or less my thoughts, Sean.

I think this sums it up and is the real crux of the matter:
Quote:
Originally Posted by Sean
There is nothing unsafe regarding the use of line cord as a dropper, providing common sense is used, checking for faulty insulation, and stiffness, usually if the cable has been bundled up tight then the cable will have suffered.
As is this:
Quote:
Originally Posted by Chris
[ ... ] accidental shorts from untidy workmanship could easily cause a dangerous explosion [ ... ]
__________________
Mike.
Mike Phelan is offline  
Old 30th Aug 2007, 7:27 am   #52
Brased
Hexode
 
Join Date: Mar 2005
Location: London, UK.
Posts: 317
Default Re: Vintage radio safety

Quote:
Originally Posted by Chris55000 View Post
"Capacitor droppers" - *DON'T!!!* I don't believe there's any type of paper/polyester capacitor on the market that will withstand a 150mA-250mA sustained current flow to run heaters in an old radio.
A modern metallised film capacitor will be well within its ratings at 50Hz. Indeed many are designed to be stuck across 230V ac supplies for suppression or power factor correction purposes. Such components are available up to several μF.

Edward
Brased is online now  
Old 30th Aug 2007, 8:46 am   #53
Nickthedentist
Dekatron
 
Nickthedentist's Avatar
 
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 15,632
Default Re: Vintage radio safety

Some interesting points, Chirs.

Although I tend to agree with most of what Sean & Mike & Ed have said, I don't think you can ever be too careful with vintage radios, especially if they're used by other people who might not be so aware of the theoretical risks.

For example, somebody recently left one of my 1930s mains sets on for hours at a time while they went out, as a burglar deterrent, which I personally feel is a bit risky.

I can still remember a neighbour's house - a subtantial, detached 1930s mock tudor place set in large grounds near Wimbledon Common which literally burned to the ground about 15 years ago, apparently the result of an electrical fault. I walked past at teatime and it looked just like it always had done, but when I went by in the evening, it was all gone, just a pile of rubble and a horrible smell

Quote:
Originally Posted by Chris55000 View Post
Transformers usually remain safe if they're not overheated due to electrolytic failures, leaky anode-to-grid couplers or shorts on dial lights! Once wax or other impregnation has stared to ooze from a mains transformer, *it is no longer safe* even if it is still running the set apparently normally.
That's interesting. Could you explain? I have read in several places that " a little migration of wax" from mains transformers can be considered normal, and will happen even in the absence of a fault condition. I often fit those little Cliff wire-ended thermal fuses in series with the mains supply, which I assumed were a reasonable precaution against severe overheating and fire.

Quote:
Originally Posted by Chris55000 View Post
Dropping resistors:- If the cement coating has started to flake off a heater dropper in the AC/DC type set exposing the elements, again the set should be considered no longer safe to test or attempt to use
Again, why? Is there any way to repair?

Nick.
Nickthedentist is offline  
Old 30th Aug 2007, 9:23 am   #54
PJL
Dekatron
 
Join Date: Sep 2005
Location: Seaford, East Sussex, UK.
Posts: 5,007
Default Re: Vintage radio safety

Quote:
Originally Posted by Chris55000 View Post
"Capacitor droppers" - *DON'T!!!* I don't believe there's any type of paper/polyester capacitor on the market that will withstand a 150mA-250mA sustained current flow to run heaters in an old radio.
I completely agree with your statement on line cord droppers - neglecting the fire hazard they also contain asbestos and I wouldn't take one in the house.
I have used motor-run capacitors as replacements. These are self-healing film capacitors with life expectancy of 30,000 hours driving inductive loads. A heater chain is a piece of cake for these...
PJL is offline  
Old 30th Aug 2007, 9:44 am   #55
Sideband
Dekatron
 
Sideband's Avatar
 
Join Date: Oct 2003
Location: Croydon, Surrey, UK.
Posts: 6,223
Default Re: Vintage radio safety

Quote:
Originally Posted by Chris55000 View Post
Dropping resistors:- If the cement coating has started to flake off a heater dropper in the AC/DC type set exposing the elements, again the set should be considered no longer safe to test or attempt to use.

"Capacitor droppers" - *DON'T!!!* I don't believe there's any type of paper/polyester capacitor on the market that will withstand a 150mA-250mA sustained current flow to run heaters in an old radio.

HT battery replacement for All-Dry sets - the Kit Radio Company's product is really the only feasable and safe way to do it if you want to make the set truly "portable". Whilst you can try stringing 10 PP3s in series, those from car-boot sales may not last very long, even with only 10mA drain. *Don't* try and make one with Alkaline or NiCd or NiMH cells - the short circuit current from even the PP3 size is tremendous and accidental shorts from untidy workmanship could easily cause a dangerous explosion that could put your eyes at risk! It is safe to use one single "D" size alkaline cell in a proper holder for filament/LT supplies.
Well we all have our oppinions and if you don't want to use most of the vintage radio's you have well that's fine.

I'll just add my own views based on 40 years experience. Firstly flaking droppers. My Pilot Little Maestro has virtually no ceramic left on the dropper. It's been like that for as long as I remember and I've had the set since 1968. It is still working fine.

Capacitor droppers. No problem with them. Thorn used one in one of their TV's back in the 70's. I've not used one yet to replace a dropper simply because I haven't needed to. No hesitation to do so if necessary provided the circuitry of the radio would allow it. As an aside, my central heating contoller uses a capacitor dropper into a regulator and it has run for nearly 15 years.

HT battery replacements using alkaline batteries. No problem...used them for years. My Roberts R55 has had a 'replacement' battery made up with alkalines for over 15 years. Never a problem. I would never use one of those inverter type things due to the amount of rubbish radiated into the set.

It's like everything else. None of these old radio's can meet modern safety requirements. Used with care however there is no danger.


Rich.


It's like everything else
__________________
On Spike Milligan's headstone......I told you I was ill...
Sideband is online now  
Old 30th Aug 2007, 9:49 am   #56
Nickthedentist
Dekatron
 
Nickthedentist's Avatar
 
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 15,632
Default Re: Vintage radio safety

Quote:
Originally Posted by Richard_Newman View Post
As an aside, my central heating contoller uses a capacitor dropper into a regulator and it has run for nearly 15 years.
So do PIR sensors, dusk-dawn switches, digital timeswitches etc. But I suppose their current consumption is miniscule.
Nickthedentist is offline  
Old 30th Aug 2007, 10:10 am   #57
Paul_RK
Dekatron
 
Paul_RK's Avatar
 
Join Date: Nov 2003
Location: Fakenham, Norfolk, UK.
Posts: 3,194
Default Re: Vintage radio safety

Many men, many standards I've nothing against line-cord droppers myself, I just wouldn't leave one connected if I were going to be gone from the room for long, and wouldn't personally use one as a footwarmer. There are quite a few models that seem hardly ever encountered without some wax around the mains transformer - I think of Pye especially as having tended to use transformers appearing to have less than conservative ratings - and I can't think of that as much of a cause for concern either. And it was usual in the 1930s for the massive ceramic droppers used in AC/DC sets to be manufactured with no coating whatsoever...

Paul
Paul_RK is online now  
Old 30th Aug 2007, 10:53 am   #58
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 21,892
Default Re: Vintage radio safety

Quote:
Originally Posted by Paul_RK View Post
There are quite a few models that seem hardly ever encountered without some wax around the mains transformer - I think of Pye especially as having tended to use transformers appearing to have less than conservative ratings - and I can't think of that as much of a cause for concern either.
The wax in transformers is there to stabilise the windings and stop them vibrating, not to provide insulation.

Paul
paulsherwin is offline  
Old 30th Aug 2007, 11:05 am   #59
ppppenguin
Banned
 
ppppenguin's Avatar
 
Join Date: Dec 2003
Location: North London, UK.
Posts: 6,168
Default Re: Vintage radio safety

Where's Ed Dinning when we need him! As the real transformer expert in the forum I think his opinion woul dbe most valuable.

I feel that Chris Williams has taken a rather hair shirt approach to safety. I'll always argue on the side of safety and I certainly don't like line cord droppers but as Nick, Sean and others have said, you often can't bring vintage sets up to modern safety standards and a certain amount of judgement and common sense are needed.

PJL's and Brased's comments about capacitors provide good evidence that capacitative droppers are safe. These caps are designed to be connected across the mains and are described as such by reputable manufacturers who wouldn't be happy if their products went bang too often.
ppppenguin is offline  
Old 30th Aug 2007, 11:39 am   #60
wave solder
Hexode
 
wave solder's Avatar
 
Join Date: Feb 2007
Location: Chesterfield, Derbyshire, UK.
Posts: 333
Default Re: Vintage radio safety

Quote:
"Capacitor droppers" - *DON'T!!!* I don't believe there's any type of paper/polyester capacitor on the market that will withstand a 150mA-250mA sustained current flow to run heaters in an old radio.
Hello,

I am in the Electric Motor trade, and the motor run capacitors that we use are often passing several amps (quite a few in the case of a 2.2Kw motor) continuously and are absolutely perfect for using as capacitative droppers in Radio's and the like. (and it is very rare when one fails and when one does they are designed to go open circuit)
wave solder is offline  
Closed Thread

Thread Tools



All times are GMT. The time now is 7:43 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.