Quote:
Originally posted by dsk
Ok, here it is after all:
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That's one fine set, like all Zeniths. I would almost put it in a class with the K-731, which is also a high-fidelity set (though your C845 probably only has one speaker, whereas the K731 has a 5x7 oval speaker plus a small electrostatic tweeter).
Replace the dial cord and the tuning knob will work again as it did when the set was new. I don't know if you've tried to power this set up, but if not, please, do it slowly, with a Variac or at least a 100-watt bulb in series with the line cord. If the bulb glows dimly when you turn the set on, you can safely continue your testing. However, if the bulb lights brightly (or even burns out with a bright white flash) as soon as you power up the set, there is a short somewhere. This is also a tipoff to a problem in the power supply in AC/DC sets with pilot lights. I have a Zenith H511 in which the pilot light immediately burned out the first time I powered up the set after receiving it from an ebay seller a couple years ago. The problem, I think anyhow, was simply that the main power supply filter capacitor (a rather large 3-section polarized unit) was deformed from years of disuse (the radio looked as if it had reposed, unused, in its former owner's basement or garage for years or decades). I replaced the bulb and the set worked well.
A deformed filter capacitor will draw so much current through the pilot light (from the huge inrush current surge) as to burn out the latter in the blink of an eye; so, for that matter, will a shorted rectifier tube, as the pilot light in most AC/DC sets is wired directly across the tube (35W4 in most later-vintage ['50s-'60s] AC/DC receivers, but it can be a 35Z5 or even a 35Z4 in some very old sets). The 35Z4 is an obsolete rectifier tube found in older sets; I once read of a Sylvania radio with this type of rectifier, but have not seen or heard of any others recently.
The 35Z4 may be replaced by a 35Z5, but not directly. There is an under-chassis modification which must be performed to use a 35Z5 in place of a 'Z4, but offhand I don't recall what it entails.