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Even with a "fully" enclosed set in a wooden or Bakelite case, wooden or Bakelite knobs, dial pointers behind a glass or plastic window, there will often be two or more chassis mounting screws with exposed heads on the underside of the case and there are, of course, the antenna terminals on a TV and most FM receivers. GFCI protection is beneficial when any vintage appliance is operated within close proximity to any grounded metal object (vents or radiators of central heating systems for example).
Any TV, radio, phono, etc. employing the "AA5 radio" power supply topology, even if the "B-" bus is isolated from chassis metal via RC networks (the GE "Locomotive" televisions: 800's; 10T1's; the wooden-case 16T1; and others used a "voltage doubler" variant of this topology) can develop a leakage path to its chassis as the new parts we install during recapping begin to age.
A shock from simultaneous contact with a grounded heating vent and chassis (mounting or antenna terminal) screw with some moderately-leaky components inside the set (perhaps 20 years after being recapped) represents little more than an unpleasant surprise to a healthy adult, but what of the 80-year-old with an undiagnosed heart condition? As a professional provider of restoration services, I encounter many clients having little or no familiarity with the technical details of the sets' inner workings. The motivation of these individuals in having a set restored may be nostalgia, perhaps the set is a family heirloom and stirs up fond memories of watching TV at Grandma's house as a child. When a client is willing to spend $900 to restore a Dumont RA-104 TV/AM/FM/Phono combo once owned by great-grandparents, complete with mechanical rebuild of the phono, correcting poorly-done repairs from 40 or more years ago, replacement of a bad yoke or flyback, fusing of the B+ line, NOS exact-replacement delay relay, along with the standard recapping, I find myself inclined to expect the set to remain a family heirloom for another generation or more. I also hope to maximize safety toward considering that there may be grandchildren visiting their homes 20 years from now.
Speaking of children, even a harmless, mild shock can result in emotional trauma to, perhaps, a three-year-old. My fascination with technology began, ironically, with a household accident at age 3 in which a defective appliance plug exploded in my hand. A teenage cousin was studying for a career as a Science/Technology teacher at that time, and transformed a small child’s fear into intellectual curiosity tempered by a healthy respect for an awesome force.
When recapping a set for a client, I also make it a matter of policy that the clients' sole responsibilities should another repair be needed within a year after recapping will be those of transporting the set here for service and cost of materials. Labor for any in-warranty repairs is always free unless the chassis has been removed from the cabinet by unauthorized persons or other tampering, misuse, or accidental damage has occurred. An instructional presentation of the set or text instructions for care and handling are also provided, and these include recommendations for upgrading the receptacle to be used for powering the set to a GFCI unit, use of a quality home-theater surge protection device, making of antenna and other signal source connections before plugging in the set's power cord, never using the cabinet as a stand for any item containing any liquid or placing hanging pots containing house plants near the set's cabinet, etc. A hanging planter above one of my grandparents' 1966 Zenith color sets proved disastrous to the 21FJP22 during watering of the plants while the set was operating and the CRT neck was at full operating temperature (splash, crack, whoosh, POW!). In those days, rebuilt 21FJP22 were advertised for only $100 installed ($20 or $25 extra without a rebuildable "bottle" to exchange), and all house plants were immediately moved far from all of the three sets for which they had paid $500 each. Only a few drops of cold water striking the hot glass was sufficient to crack the tube, spoil its vacuum, and cause a spectacular display of arcing inside the set.
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