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In other related news, I recently acquired a Hickok 610A TV/FM Alignment Generator. This model seems to be among the better quality self-contained instruments of the time for this purpose. Recapping and calibration are in progress.
The upgraded Eico 368 seems likely to become my primary alignment instrument for pre-color IF systems, although the dial gear drives seem less precise than those of the Philco 7008. On the Philco unt, there is almost no mechanical backlash in the dial mechanism, while the Eico drives' backlash is quite noticeable. The lack of a 1/10-division vernier for its 0-100 linear scale on the marker dial was another minor inconvenience, although I have since created a decal having the correct markings printed to proper scale which is now affixed to the faceplate in the proper location.
Regarding the Eico 368 in general, the unit bears some signs that the manufacturer's Engineering and Accounting departments may have had some disagreements in which Accounting seems to have overruled Engineering The schematic, for example, shows the 6.3 VAC tube heater circuit having neither side grounded to chassis, while the kit assembly instructions and ultimately the construction of the unit itself not only had one side of the heater circuit directly connected to chassis ground, but actually employed the chassis as a conductor for heater current. Having also studied the manual for the Eico 369, it appears that Accounting and Engineering reached a compromise of sorts regarding heater wiring, since the heater circuit of the Eico 369 is shown wired in twisted-pair configuration with one side tied to ground. Isolating the heater circuit in my Eico 368 from the chassis, making its ground connection to a single point, and ultimately converting cathode and grid returns of some of the most sensitive circuits to star-ground configuration significantly reduced 60 Hz noise content of the Scope Vert output. Prior to the improved configuration, the Vert output consisted of the desired output riding on 60 Hz AC of 150mV p-p. After the breaking of internal ground loops, the amplitude of the 60 Hz noise on the Vert output is down 20dB at 15 mV p-p. The only way to improve further upon that figure would seem to be to reverse the assembly instructions of the kit step-by-step, replace all heater wiring with twisted pair, and change all ground connections to star configuration. If I were to eventually do that, I would probably also add a Hum Balance pot for good measure.
Since I'm partial to the "X" (actually, a mirrored "S" curve) display for FM Detector alignment, I'll be replacing R28 (10K-linear "Sweep Width" pot) with one having a "push-off/pull-on" switch and wiring the switch between pin 3 of V3 and R23. With the knob in the "out" position, blanking will function normally. Blanking will be disabled with the knob pushed "in" so that the "X" pattern can be displayed with proper scope settings.
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