1977 Zenith Chromacolor II 25HC45

[radiotvnut]

I tested the jug and it took the blue a little while to come up, but it eventually woke up (the set probably has not been turned on in 30+ years). As far as delta-gun tubes from that era, Zenith tubes held up the best.

[Electronic M]

Originally Posted by radiotvnut

I tested the jug and it took the blue a little while to come up, but it eventually woke up (the set probably has not been turned on in 30+ years). As far as delta-gun tubes from that era, Zenith tubes held up the best.

Yeah I just had a CC CRT surprise me at how tenacious it is. A year ago I got a 25" Zenith 4-tube hybrid in the Avanti cabinet from a local radio/TV hobbyist who from some point in the 70s (he got it used) until the prior year (when he got a flatscreen) had been using it as his main TV...The set had been in continuous use since new. I figured he might have replaced the CRT as it still worked decently. Getting picky I recently noticed (when I finally got it from storage to home) that it's slightly dim for a very bright room and focus is a bit soft. Focus was at one end of the range, and I've seen focus dividers on these drift so I added 5 megs in series with one end of the pot to shim it. That fixed that but focus wanted to be less than perfect (still fairly acceptable, but not knock your socks off good like I would expect) at normal brightness. Then I decided to do a grayscale and found that after adjusting the screens right it looked too green and there was no green bias pot and red and blue were at max...So I turned the green screen down for acceptable balance. Sensing something was off I decided to test the CRT...

To make a long story short: the CRT was testing at %10-15 on my B&K 466 where most other color tubes that touch the bottom of the good range (which is %50) look worse and dimmer.
To put it further into perspective the scale on the B&K is calibrated for color tubes where %85 of the guns output is blocked by the shadow mask... Monochrome tubes that don't have that limitation will typically act like a weak color tube when they get below %30....That Chromacolor tube was putting out a good picture at half to 1/3 of what an aluminized monochrome tube needs to look OK. Unbelievable!

Zenith Chromacolor CRTs are good to the last drop.

[zeno]

Interesting thing is D - E ( & maybe C ) line SS flat chassii and
E & maybe F line CC2 AND 12, 16" Zenith Taiwan B&W hybrids were
instant on. IMHO it shows instant on is not a bad thing when used
on a SS set. It should NEVER be used on an all tube PCB built set,
especially with compactrons ! I would always defeat it on those
sets. Its as easy as snipping one end of a diode in most sets. We used to
do it for a few bucks when a set came in if the customer wanted.
Turned out to be an obscene profit center !

73 Zeno
LFOD !