[earlyfilm]

Eric, I have an example while not pertaining to running at lower voltage as you mentioned, might give a clue.

Back in about 1971, I was just married, had a new daughter, a newly purchased house and not much money. I had owned an all tube 1965 16 inch color Sears (rebranded Toshiba) since 1966 that had just developed the habit of cutting * out at random times and my wife was insisting on either fixing that set or preferably getting a larger one. I found a used Zenith with a booster on its almost dead CRT for practically nothing, at the same time as our local rebuilder was running a special on rebuilt color CRTs.

I got the old Zenith home, confirmed that the CRT was very VERY dead and it took about 20 minutes to get to viewable brightness with the booster and even then only bright enough to watch at night. Wrote down the CRT number and trotted over to the rebuilder, who promptly told me that he did not rebuild Zenith CRTs. Aaaarrrrrrgh! This means that I'm stuck with two bad sets!

OK, what next? I scrounged an old 6.3 volt transformer from my junk box and wired the CRT to be on 100% of the time, as that would eliminate the 20 minute wait and give me a little thinking time. Early the next day, when the set was turned on, I noticed the set was brighter than before and so I removed the booster, and it still was OK. We used this set operating the filament at its rated voltage and always on when the set was off for about 10 years! The filament pulled 6.3 volts at 3 amps, or about 19 watts. That was less than our security lights.

The CRT still put up a good picture to the very end, which happened when the horizontal output, damper and flyback cremated themselves in unison.

My theory is the constant CRT heat enabled the getter to do its job better.

The point of this is, if you use the set, keep it on long enough for the heat to warm up the getters to keep the CRT healthy.

James

* This is before cooling spray was available. The problem turned out to be a 5 cent intermittant resistor, but as the problem always fixed itself as soon as I touched a probe anywhere, almost no useful circuit tracing could be done and the voltages were within 10% when the set was operating and could not be measured while it was acting up. The trouble was finally pinpointed when I disconnected the AGC keying and used a battery to hold the AGC voltage constant.