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Main => Monitor/Video Forum => Topic started by: SavannahLion on November 09, 2007, 11:32:33 pm

Title: Cracked tube?
Post by: SavannahLion on November 09, 2007, 11:32:33 pm

Even after carefully examining the tube, I have no idea if the tube actually works. (Wells Gardner K7191)

Since I currently have no working PCB to test with, is there any other way to at least get a basic idea if the tube in question has been gassed out or if it's something worth testing?

Title: Re: Cracked tube?
Post by: SirPeale on November 10, 2007, 07:13:10 am

Only if you have access to a rejuvinator.

Title: Re: Cracked tube?
Post by: SavannahLion on November 10, 2007, 11:29:51 am

So to even find out if a tube is worth salvaging, I'd have to have a working PCB or a rejuvenator. Great.  :banghead:

Oh well... maybe I can cannabilize the two non-working PCB's I do have and make one working board before I start ordering parts.

Title: Re: Cracked tube?
Post by: FrizzleFried on November 10, 2007, 01:07:53 pm

Fire it up and turn up the screen pot...see if it even lights up.

Title: Re: Cracked tube?
Post by: SavannahLion on November 10, 2007, 08:32:22 pm

Quote from: FrizzleFried on November 10, 2007, 01:07:53 pm

Fire it up and turn up the screen pot...see if it even lights up.

I did fire it up. The flyback popped. The other is missing a daughter board that I need to remove from the other. IOW, I need to rebuild at least one board somehow.

Title: Re: Cracked tube?
Post by: qrz on November 13, 2007, 11:13:04 pm

most vacuum tubes have a visible silver looking material called a "getter" inside the glass envelope.

this material will change (color) to a white powder when exposed to air . 

 also if vacuum is lost , the "heater" filament should burn out upon applying power and

there would likely be arcing inside the gun assy' when high voltage applied .

typical 2nd anode is around 30kv for a 25"+  crt

qrz