widow maker ethics question

[Randall]

Seems the widow maker subject has come up a few times here recently. I have a customer bring me an very cool looking Zenith tube radio from the way back when. It has no PT, no fuse, and it works, but hums. He asked me to fix the hum because his wife likes it. There is no real estate for an iso transformer. At first I thought about installing a plug with either a 3 prong or a 2 prong with different sized blades so it can only be plugged in without the chassis being at 120v, but this assumes that every outlet will be wired correctly. If not, I have "faked" a plug that makes it so it can possibly only be plugged in wrong and be potentially lethal.

So, I know he likes this cool old radio, but my question is how many of you would try to do what this customer wants, and how many would not take the work, because you know someday, somehow, someone is going to get electrocuted to some extent, and can't live with that fact or the liability trail of being the last person to have worked on it?

I'm leaning towards telling him I can't help him with this one, and maybe just use it for decoration.

[Enzo]

Well, we don't like anything with a hot chassis, however, a table radio, unlike a guitar, is not played while holding metal connected to its chassis. The chassis is exposed via the screws on the bottom, and maybe something exposed in back. But the part they usually touch, like the knobs or case, is not conductive. That is why they got away with it all these decades. And 60 years ago, it was accepted that when you plugged something in and got shocks, you had to turn the plug over.

You can tell them that back then, people did in fact get electrocuted now and then, there was no such thing as a GFI on the bathroom outlets. Nothing was grounded.

You COULD tell him that this technology came from before safety was a concern, and you are ethically bound not to do anything that endangers them, like fix it.

But you could also offer to make them a "safety box". There is no real estate in there for an iso, but the iso doesn't have to be very large. You could mount one in a nice little enclosure with a power cord and an outlet. Now they plug the iso into the wall, and plug the radio into the safety box. Make up a classier sounding name for it if you want. The box can sit on the floor or behind the radio.

You know what a wall wart is, little DC adaptor. There are some slightly larger ones that have a two wire power word to the wall and a thin cable with a barrel connector for the equipment end. We call those floor warts or power bricks. You could probably make an iso box in one of those cases.

Then a few filter caps is likely all it needs. At worst a bunch of leaky film caps as well.

[tubeswell]

I got asked to convert an old transformerless phonograph into a guitar amp a couple of years ago by a friend at the time. And I refused. That dude hasn't spoken to me for a while. He always looks suspicious at me if ever I bump into him at the blues club jam nights these days. But I'm not going to be responsible for his death.

[Mick Bailey]

The reservation I have with an iso box is it could get separated and some future owner could plug the set into a regular wall outlet. For me, I'd let the odd job go if there was a possibility of something going wrong.

I see a few old portable record decks where the neutral mains connection is wired as a signal ground. No isolation transformer, and they have an unmarked figure-of-eight two-core mains cable. Now, if the wiring to the plug gets reversed the chassis and signal ground becomes live. 120v is one thing, but our mains is 240v, often more. The chances of severe consequences goes up many times at this voltage. Often there's just too much work to make those things safe, compared to the value in the equipment. When you start looking at them critically mains isolation is just one aspect - plywood standoffs, pot shafts at mains voltage, poor insulation........

[EFK]

I'd not touch it without being able to properly hardwire in an iso transformer. Look at it with the perspective of your personal liability if for no other reason.

[R.G.]

Tell him that you have too much respect for life and other people to participate in a dangerous situation. Then explain why.

Tell him that, like children, humans are discovering what is hazardous and how to sidestep the hazards as we grow and learn. We know a lot more about electrical safety now. Describe the unit as a box with a poisonous snake inside. It's fine - until the box accidentally gets opened or a little bit broken and someone reaches inside.

[Tom Phillips]

You could build a small iso transformer box and hard wire it into the line cord. Similar to the way GFI units are put at the end of a hair dryer cord or in line like an AC adapter for a computer. Just don't use any connectors between the radio and the AC plug.

Re: "There is no real estate for an iso transformer." That's surprising. Those old radios were not that tight inside. It doesn't need to be mounted directly on the chassis. You may want to consider mounting the iso and a fuse on a flying bracket connected to the chassis or the case.

Edit: Comment - Yea...projects like this can be a lot of extra work. When I decide to take on such a project it is a labor of love, a favor for a friend or the customer is good with the appropriate shop charge.

[olddawg]

What is the current draw? These series filament amps generally are low powered single ended amps. I find it hard to believe there is no room for a small isolation transformer somewhere, even if you epoxy it to the cabinet. And yeah a small project box hard wired to the cord or mounted on the back will work too. The down side to that is the primary will always be energized.

[Randall]

You guys will just have to trust me, there is no room for a transformer in the chassis, or any where else. It's a table radio. But I do like the iso in a box hardwired to the new grounded line cord. And so does my customer, who's wife really wants the retro cool looking radio to work. So there we have it. He said, if you can do it for under $200, do it. Done.

[J M Fahey]

IF no space in the original cabinet (don't just epoxy it, use some bolts and washers, even add a small metal plate as a sub chassis) you may mount the safety transformer in an oustside case, pick one, but do NOT use a regular mains plug between amp and iso tranny, choose any Industrial type connector you wish, male on the amp "mains" cable, matching female on ISO box so there is NO WAY the amp can be directly plugged into mains, even by mistake.
Something like the Cinch connectors:


Not the 2 pin ones, because they superficially look very much like old 110V flat blade plugs, and somebody might be tempted to replace them, but the 4 pin one (even if you just use 2 or 3) , they *look* complex and impressive to the un initiated and nobody will even think about replacing them with standard 2 or 3 pin mains plugs .

[Enzo]

And make sure the MALE goes on the chassis and the female on the power cord. NEVER put hot on male pins, they can touch anything nearby.

[Randall]

I'm not going to use connectors, I'm going to hard wire it. Sorry for the slight inconvenience so that you or anyone else does not get hurt. Done and done.

[Leo_Gnardo]

Good plan & I hope your crustomer & his wife will get many years of enjoyment listening to old radio shows on their old radio.

[rjb]

...many years of enjoyment listening to old radio shows on their old radio.

I used to have one of these guys with the Magic Eye.
Unloaded it for two reasons- it took up too much space, and I got sick of Fibber Mcgee and Molly.

[Randall]

Can someone help me figure out what rating iso transformer and line fuse I would need for this? It is marked 30 watts on the label, and curiously "Volts 117 AC/DC 60 cycle".