21AXP22 tragedy

[ohohyodafarted]

Charles,

Rate of heating and cooling is the key to successful rebuild of all crt's with a metal shell. You have to ramp up and ramp down very slowly. At Hawkeye, the oven cycle for a metal tube is 6 hours long, (as opposed to 3 hours for an all glass tube) using a very long and slow ramp up and ramp down. Then the tubes sit in the oven overnight to cool to room temperature. I suspect that Dunbar would have been succesful with your tube if he had just left it in the oven overnight to cool down instead of taking it out of the oven and puting it on the cooling rack.

I read somewhere that there was a seperate cooling down oven that was used on metal tubes after they exited the old pump down production lines, in order to bring the tubes down to room temperature at a very slow rate.

Bob

[jeyurkon]

Could be something as simple as a thermocouple gone bad in his oven too.

John

[ohohyodafarted]

Nope, not a thermocouple. Scotty has two independent temperature sensors in the oven. One drives the controller and there is a second that just monitors the oven temp. Both were in agreement within about 5 degrees. So 600F was pretty much right on the mark.

[WA3WLJ]

RE : I'M THINKING 30 HOUR BAKE - OUT