I am still hoping to find someone familiar with this generation of Zenith chassis. Zenith used this chassis design for many years. I have been squawking about this old Zenith forever, so I am going to just take up where I left off in other posts in regards to repair attempts to try to keep from repeating everything. Anyway, today I used a megger to check the winding insulation integrity of the vertical output transformer in hope of restoring vertical sweep. I didn't find anything wrong with transformer, however, I did find that the vertical hold potentiometer gives erratic resistance readings. Perhaps that will be a lead in the vertical trouble.
NOW, I was wondering if anybody knows much about the video detector diode M2 . I was surprised to find a solid state diode on a 1958 schematic, but there is one there with a couple of inductor coils in the third video IF stage. One of the coils (L6-81mH peaking coil) that is directly connected to the diode is open. I have a volume adjustable hum for sound and I was just wondering what effect, if any, that this bad diode and open coil may have on anything other than obviously the video section. Could it produce the hum if say it was shorted? Also, would it show the same or similar readings as any other solid state diode like a 1N4004? Could I use the 1N4004 as a replacement? I am hoping in a big way that this might be at least a lead in getting somewhere with this old Space Command. This was a re-cap with no positive results and I have never been able to do voltage checks due to the lack of a test crt, so I am stuck with an ohm meter as my only weapon for now. These were supposedly great performers and ther is no reason why I shouldn't be able to get this thing going. I would love to have a large 24" screen, fifties REMOTE set for daily use!
12-16-2010, 12:07 AM
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