CRT restoration help

[Zsuttle]

So, I have a few CRT’s I’ve collected over a few years and I’ve been wondering what’s the proper sequence to bring them back into working condition. Like after checking emissions, if emissions test bad, should I run the filament voltage high for a while? I’ve heard that on a completely dead tube, running the filament (6.3v) at 8v for a few hours will sometimes help emissions and then one minute at 9v. AKA can someone sum up what to do if a tube tests different ways?


If the tube reads completely dead, what’s the first step?
If I get some emissions, what’s next?
If none, then what?
I have a B&K 467, when should I use the restore and rejuvenate features?

[Electronic M]

On CRTs that have gone unused a long time my typical procedure on my B&K 466 is to do the typical check emission procedure at 6.3V and if it starts bad I let it sit on the tester in 6.3V emission check mode like that for as much as an hour. If still stone dead or very weak I'll bump the heater to 7 or 8 volts (depends on how strong of a nudge I feel it needs) and let it sit as much as another hour. If after that there is barely any emission reading above 0 I'll get a wooden dowel and start wacking the neck (hard, but not enough so to break it), as I wack it I try the rejuve settings one by one till I get improvement or failure.

If it stays stone dead 0 emission that usually is open cathode I deal with that by reflowing the solder on the base pins if it has a base like that, then recheck and do the reweld procedure in the tester's manual.

On my 466 I've found that the good bad scale is more geared toward color CRTs that need higher emission for a given brightness. Upper bad and "?" monochrome CRTs often are bright enough to use in normal room light if the chassis driving them is good and was engineered to give the tube plenty of HV...I prefer strong tubes, but in some cases taking "probably usable" is the best/only option. I'll often avoid doing a rejuv on an upper bad monochrome CRT (unless I know it is too dim to use) as I feel the possible improvement is not worth the risk of burning it out on a rejuve.

[maxhifi]

Tom, this advice is very timely, you saved me from frying the CRT on the Marconi I'm working on. I think a sticky could be in order.

[kramden66]

Don't forget if you can get good emissions from a brighter you can go with that also , correct me if I'm wrong but you get more time from a brightner and there's no risk of instantly killing the CRT.
I have the b&k 465 and when I have a CRT that's not comming up I will try like stated letting it sit at 6.3 for an hour or as stated 8 volts for an hour , ifthst fails and its really weak i try the remove shorts first , correct me if that's not a good thing o do , I really kind of gave up on rejuve because they didn't last long , one was about a month to two months , one was a week .
On the 465 I found this to be common , a 10BP4 even if it's halfway in the bad will show a picture that's good , a 12LP4 has to be in the higher area of bad up to ? If it will show a good picture , 16GP4 at the edge of bad close to ? To show a good image , predicta tubes 21 and 17 around the upper part of bad maybe even halfway up into bad.