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Old 01-18-2018, 11:27 AM
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old_tv_nut old_tv_nut is offline
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Join Date: Jul 2004
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This brings to mind the fact that the early color CRTs needed resistors in the HV feed to prevent strong arcs from damaging the guns. Redesign of the CRT's internal discharge path fixed this, but later sets sometimes used limiting resistors to prevent arc damage to other components besides the CRT. If a set has such limiting resistors designed in, it should be able to withstand short circuit discharge when the set is off.

In my earliest job at Motorola, I did arc testing on a new chassis, which was done with the set running for maximum safety factor. The discharge path in a particular chassis can be very circuitous (no pun intended). One Motorola solid state B&W had a problem with CRT arcs killing the sound section. The arc was going into the B+ supply via [Edit: the CRT grid 1 vertical blanking coupling capacitor to:] the vertical sweep transformer, and then through the audio output transistor (no damage along the way) to the audio driver transistor, which it would kill. The initial fix was to use a beefier audio driver, and eventually a choke coil in the driver circuit to squelch the initial transient.
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Last edited by old_tv_nut; 01-18-2018 at 09:08 PM.
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