GFI for safety

[K6JEK]

I'm working on a 1940 Zenith (see thread 1930 Zenith) which I know will end up in a room with two wire, no safety ground AC service, not my room, the room of my friend who owns it.

Meanwhile the thing scares me.  In addition to the usual problems, bad electrolytics, bad paper caps, and bad tubes, it has bad insulation on the wires.  The cloth insulated wires are fine but the rubber insulation on others has gotten brittle and cracked and flaked off in many cases.  I've been slipping heat shrink tubing or spaghetti over these bad guys. In some cases I replaced the wires altogether.  But what about the ones I miss or the insulation inside the power transformer?

It will be leaving my hands with a three wire cord and a fuse.  What else should I do?  I believe it is actually legit in the NEC to install an ungrounded three prong GFI as long as it's labeled as such, i.e, nothing hooked to the ground pin.  I'm not recommending that but are there small GFI's I could install in the case to get the same effect, one more level of protection?

[KB2WIG]

Offer to install the gfi in friends room not the radio.... the code (but maybee not the local jurisdiction) lets you do what you wanted to do.

 Your correct; paste a
                                    " No Equipment Ground "
                          
                                                                      sticker on the outlet.

Just so you know, if you get across the line and neutral in the protected outlet , you still can get zaped.

THEN        What i usta do was to make sure the friend tightened a few wires so as to share liability.
NOW         Personally, I will not do any type of home wiring for friends as I don't have enough money             for insurance. Any problems, guess who they come to see.


klc

[Jim, W5JO]

If you are that worried about the safety aspect of this project, then don't do it.

In today's world even the smart people can find a way to hurt themselves, don't give them the method or ammunition.  When it comes to money, greed rules and stupid lawyers abound.

[Ed/KB1HYS]

late 30's early 40's Zeniths used a rubber insulated wire that by now has turned into a crumbling dust coating.  The only real option is to rewire the set replacing all the rubber coated wires with new wire. This is a lot of work, especially removing the band switch, but it's really the only way to get the set safe from shorts on the crappy wire.  The cloth covered wires seem to stand up very well, as long as they are protected from chaffing and critters etc.

Good luck.

[SM6OID]

Hej !

Well, I would say that it is a must to have a proper ground. All of my boatanchors do have three wire cords, the outlets do have ground and I have a 30 mA ground fault breaker installed in the electrical central to protect all the outlets.

We have 230 V in all of the wall outlets, so the risk is somewhat higher than for you guys with 120 V. However, getting a 120 V shock is not nice either, and can lead to a permanent condition...

Conclusion and advice; it is a big responsibility to repair/overhaul a old radio, possibly things can go wrong even if you did the right thing or did what "the customer asked for". IF then things go wrong you may end up in a nasty situation. IF I knew that the radio will be connected to an outlet without ground I would refuse to do the job with the radio. I also would like to comment the use of ground fault breakers, remember that the usually protect the equipment very well, and usually it reduces the risk for personal injury a lot, but it is not 100% safe.   

[flintstone mop]

Hej !

Well, I would say that it is a must to have a proper ground. All of my boatanchors do have three wire cords, the outlets do have ground and I have a 30 mA ground fault breaker installed in the electrical central to protect all the outlets.

We have 230 V in all of the wall outlets, so the risk is somewhat higher than for you guys with 120 V. However, getting a 120 V shock is not nice either, and can lead to a permanent condition...

Conclusion and advice; it is a big responsibility to repair/overhaul a old radio, possibly things can go wrong even if you did the right thing or did what "the customer asked for". IF then things go wrong you may end up in a nasty situation. IF I knew that the radio will be connected to an outlet without ground I would refuse to do the job with the radio. I also would like to comment the use of ground fault breakers, remember that the usually protect the equipment very well, and usually it reduces the risk for personal injury a lot, but it is not 100% safe.   

YA tell mke about two prong 220. We were in the Philippines and I was scared everytime I would plug something in!!! There was always a spark sound when I plugged anything into those sockets.

FRED

[K6JEK]

Thanks for all the suggestions.  I think I'll go with all of the above. I'll continue re-wiring. Get my friend Craig, the owner of the radio, involved so it's not just me making the calls. Get him to install a GFI on that outlet (I'll hand it to him). Put on the three wire cord and fuse as I planned.

If only it were more of a radio!  This is the first old Zenith console I've worked on.  I'm struck by how much wood, how little radio even for the era and by what I'd call haphazard construction.  My SX-28 is a fabulous beast.  This Zenith is a fabulous piece of furniture.

End editorial.

[k4kyv]

The safest approach would be a small isolation transformer.  It would be inconspicuous inside that roomy old wooden cabinet with the little table-top radio chassis and big speaker. I assume you can still buy them.  I  have often seen used ones at hamfests.

They built over-hyped crappy stuff in the 30's just as they do to-day. A common trick was to add superfluous tubes because of a perception by the public that the more tubes the better the set.  For example, they might use a 6F5 1st audio stage and a second 6F5 with the grid tied to the plate to make a diode detector, rather than using a single 6Q7 triode with built-in diodes for detector and AVC. Sometimes a series-strung set would have an extra tube or two that served as nothing more than a filament ballast. The other tube elements would be grounded or left with no connection, and blank tabs on the socket would be used as tie points to make it look like the tube was actually part of the circuitry.

[Ed/KB1HYS]

I do have to admit, the Zenith 10S566 that I've had was pretty shabby in the construction department, and the schematics don't necessarily tell the tale either.  It seems that as long as it worked coming off the line it was ok.  I'm leaving the circuit as built when I repair it, regardless of what the schematic says, it did work the way it was built.  I do have to wonder if someone tried to repair it sometime along the way...

You can also get stand alone GFI's that go "inline".  Putting one of those inside the wood chassis, hardwired into the line cord wouldn't be too bad an option.

[w1vtp]

The safest approach would be a small isolation transformer.  <snip>

Don

Yer right

Al