It followed me home... Philco roundie

[yagosaga]

Originally Posted by RetroHacker

Well, I got the schematics and did some voltage checks. These are all measured from chassis ground:

Screens:
Pin 3 (Red) - 435v
Pin 7 (Green) - 433v
Pin 11 (Blue) - 435v

Grids:
Pin 2 (Red) - 72v
Pin 6 (Green) - 87v
Pin 12 (Blue) - 80v

Plates:
Pin 4 (Red) - 182v
Pin 5 (Green) - 191v
Pin 13 (Blue) - 181v

So... I'm getting voltage into the tube. All three filaments light. Why no green?

I believe that you measured positive voltages, yes?

These voltages are OK. It seems that the green gun is weak. Try the following: turn the screen voltages for red and blue as low as possible with the screen controls. So you probably will get something around +300v. Increase the green screen voltage up to 700 or 800 volts. The screen should be green now. Does it?

If it is so, I will explain you the next step.

- Eckhard

[RetroHacker]

No, I can't get green no matter what I do. I tried adjusting the screen contols. And I can't really even get a full clean bright color of red or blue either. But, I do have one new bit of test gear, accquired just today. The B&K Precision 470 Picture Tube Tester.

I finally own a picture tube tester! A couple of the adapters are missing, but, the round color tube socket is here, and that's the one I need.

So, I read the manual for the tester, and hooked it up. I found that I was totally unable to set the G2 cutoff for green at all. Red and blue went OK. Then, I checked emissions. Red is in the BAD, green doesn't even register, and blue is in the ?? between GOOD and BAD, but just barely. Well, that explains it. This tube is completely shot.

So, this project is on hold, until I can find a picture tube.

-Ian

[Bill R]

You might try raiaing the heater voltage a bit and let the tube sit at the higher voltage for a while. That might get the emission back up, especially if the tube has been unused for some time.

Bill R

[radiotvnut]

If raising the filament voltage does not work, you can try rejuvenating it with the 470. Actually, the 470 has a "clean and balance" and a "rejuvenate" setting. You might could try the "clean and balance" function first. I've had much better luck with the rejuvenate function on the 470 than on the older 465 tester. At any rate, you have nothing to lose. The tube is not doing you any good in it's current state and rejuvenating it might give you enough life to find a decent tube.

[yagosaga]

Please do not overheat or rejuvenate the crt at first. I had a crt which was absoltely weak on green when testing the set:

http://bs.cyty.com/menschen/e-etzold...firstLight.jpg

After running the set for some hours, the crt was self-rejuvenated only by operating the set:

http://bs.cyty.com/menschen/e-etzold...irstLight2.jpg

Some picture tubes are weak when they were not operated for years or decades.

If this procedure does not work, you can rejuvenate the crt.
I had another crt, which was absolutely dead on red and very weak on blue and green. After rejuvenating, the crt was so strong as a new one:

http://bs.cyty.com/menschen/e-etzold...inBetrieb2.JPG
http://bs.cyty.com/menschen/e-etzold...r_Sept2007.JPG
http://bs.cyty.com/menschen/e-etzold..._Sept2007a.JPG

and this strong guns now lasted for years.

- Eckhard

[andy]

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