Quote:
Originally Posted by Tubejunke
I am just curious as to how this aspect panned out for you. I am working on a similar vintage Zenith and your findings are almost identical to what I was finding in my set except I can't get 190mA. More like 200 or maybe 210 at 110V. My flyback seems hotter than I would like it to be after about 30 minutes of operation. I am waiting on a replacement socket for my HV rectifier which was burned up and the 1W resistor was open (blasted in two).
I had long been searching for the source of a very light HV hissing that was intermittent. It couldn't be seen down inside the insulating cup of course. I think that we should be able to achieve correct cathode current at full line potential. Like you, I used a variable source to control this, but I don't think it would be necessary to use that or alter the line voltage in a healthy set. Also, I found that just having the raster fill the screen is not guite all my set needs. The higher line voltages (above 110V) around 115V or up give a much crisper or clearly defined picture once video comes into play.
|
I have been attempting to align my IF so my set has been on for up to a couple hours at a time. I still have my Simpson 260 in series with the HO cathode and have been keeping an eye on it. So far it is holding at about 190-195 mA. I turned it off after it had been on for over an hour and felt the flyback. It was certainly warm but not burn you fingers hot. I will use an IR thermometer on it next time I have it on for a while and report the result. If it would help, I can also take some voltage readings. You may want to replace all of the capacitors in the HO section and verify that all of the resistors are within their tolerance. A leaky HO grid cap could elevate your current.
Dave