Safe use of an old valve radio

[joolsmy]

Apologies if I'm posting this question in the wrong forum. I have an old valve radio that has been rewired internally so is basically sound. The problem is it has no provision for a protective earth, the internal chassis is wired to neutral (was live before rewiring!) and it is far from double insulated. The control knobs are on brass rods which obviously protrude from the wooden case, so pose a risk (they are mostly concealed by the bakelite knobs but you could slide a nail file behind them and contact the rods). The grub screws in the bakelite knobs are recessed and have been covered with a non-conducting wax-like substance but a determined poke with a sewing needle would probably break through to contact them.

Given all the above plus the ventilation holes in the back cover, would a permanently wired RCD plug provide sufficient protection?

 

[Specialist]

Good to see there are a few valve radio enthusiasts around. I have over 40 of them myself. OP could probably use a mains isolation transformer.

There's really no reason, they're perfectly safe to use If properly restored & used correctly. The problems start when people turn them straight on at full voltage after 30 - 40 years lying idle, Don't have them correctly restored, use them with the chassis Live or start playing about inside them / poking a screwdriver in to adjust things without knowing what they're doing.
Over the years I've restored & repaired many vintage radios & other electronic equipment for people and never heard of anyone getting shocked or electrocuted by a vintage radio.

 

[sparkdog]

Yes, not really a cause for concern. Must have been millions of AC/DC tellys and radios out there at one time. Used to be routine to check the mains polarity with one's trusty neon screwdriver on every callout.

 

[dmxtothemax]

QUOTE - [OP could probably use a mains isolation transformer.]
this was going to be my suggestion
But someone beat me !

 

[Specialist]

Yes, not really a cause for concern. Must have been millions of AC/DC tellys and radios out there at one time. Used to be routine to check the mains polarity with one's trusty neon screwdriver on every callout.

Gawd let's not start the neon screwdriver debate again, you'll get us lynched . Totally agree with you though, Neon out & touch chassis before fingers in & touching chassis used to be drummed into you. Saved a lot of experiences .
Still got a couple of the old Black testoscope screwdrivers & use the same routine to this day before delving into.

 

[davesparks]

What concerns me in threads like this is that people seem to think that an RCD will prevent an electric shock, it does not.
An RCD reduces the duration of an electric shock if you receive one, this reduces the amount of current which flows through your body to a level which won't be deadly to the average perfectly healthy adult.
You will still get a shock from an RCD protected circuit, and from experience I can tell you that the time it takes to trip feels like forever and it hurts like hell.

 

[joolsmy]

What concerns me in threads like this is that people seem to think that an RCD will prevent an electric shock, it does not.
An RCD reduces the duration of an electric shock if you receive one, this reduces the amount of current which flows through your body to a level which won't be deadly to the average perfectly healthy adult.
You will still get a shock from an RCD protected circuit, and from experience I can tell you that the time it takes to trip feels like forever and it hurts like hell.

Fear not, there's lots I don't know but I do know how an RCD works. I would be interested in any advice offered on mains isolation transformers though e.g. how best to use one with my iffy valve radio. I should add I think I understand how an isolating transformer makes the appliance safer, it's more a question of what's available and the best way to implement it. Ta.

 

[Specialist]

Fear not, there's lots I don't know but I do know how an RCD works. I would be interested in any advice offered on mains isolation transformers though e.g. how best to use one with my iffy valve radio. I should add I think I understand how an isolating transformer makes the appliance safer, it's more a question of what's available and the best way to implement it. Ta.

Please tell me what makes you think you need one ?. Why do you think the radio is unsafe as it is ?.

 

[freddo]

I have several isolation transformers here, but they only get used on ac/dc stuff if they're being connected to earthed test equipment. If it has been modified with a capacitive dropper it is likely to have been fully serviced and is ok to use. I use mine all the time and don't worry at all.

 

[Specialist]

Hi freddo: Quick question for you buddy, Just out of interest. What radios do you prefer Woodies or Bakelite.
I'll work on anything but my preference for collecting is Bakelite.

 

[freddo]

A bit of both really, but if I had to choose it would be a nice 1930s wood console, I have several nice Murphy consoles here, their electronic and cabinet designers were really ahead of their time.

 

[Specialist]

Murphy consoles are nice, a lot don't like Murphy but I think they were mostly well made & had good sound quality.
I'm pretty partial to Bush as well, only 2 radios I kept when we moved was a DAC10 & A 90A.

 

[joolsmy]

Please tell me what makes you think you need one ?. Why do you think the radio is unsafe as it is ?.

Mostly the reasons I stated initially. If I compare its construction to a modern class 2 appliance it falls short in a number of areas and could not be retailed legally if it were a new item. I have to assume that all the regulations governing a new item are there for good reasons. Some forum members mentioned mains isolating transformers, I'm not in a position to dismiss their opinions off-hand. I feel I owe it to the other members of my household to explore all possibilities. This probably does sound over-cautious to a lot of readers, but bear in mind my lack of knowledge and experience.

 

[Specialist]

I fully accept your lack of knowledge & experience, you cannot compare a Vintage radio to a modern double insulated appliance. You have to accept that Vintage equipment was made to a whole different set of standards.
I don't understand what you find so Dangerous about them. As long as the chassis is securely bonded to Neutral, You fit the correct fuse for the item preferably 2 amp max, the back is securely fitted & in good condition and the case is not badly damaged allowing finger access. Use it and enjoy it, like a lot of the rest of us do on a regular basis.

 

[joolsmy]

I fully accept your lack of knowledge & experience, you cannot compare a Vintage radio to a modern double insulated appliance. You have to accept that Vintage equipment was made to a whole different set of standards.
I don't understand what you find so Dangerous about them. As long as the chassis is securely bonded to Neutral, You fit the correct fuse for the item preferably 2 amp max, the back is securely fitted & in good condition and the case is not badly damaged allowing finger access. Use it and enjoy it, like a lot of the rest of us do on a regular basis.

I do use the radio and I don't think of it as dangerous, I just wanted to ensure I was using it in the safest way possible. As it happens it's fitted with a 3 amp fuse so I'll take your advice regarding a 2 amp fuse. Thanks.

 

[telectrix]

3A is fine. don't forget that the plug fuse is there to protect the flex, not the radio. that will likely have internal fuse/s.