1949 RCA T-120 Picture tube conductive coating question

[ketron281989]

Hi guys, thanks for all your answers on the HV topic I posted today. I have recently been digging more into this T-120 just for a cleaning and tube testing procedure I do with all my sets once bought. I came 1 new issues that I have never had to deal with.

I have now noticed that the coating on the CRT which is a 12LP4A (test quite strong) is flaking off quite a bit just from me handling the CRT. I know when I go to clean it with a soft cloth, the coating will fall right off. Is there a way to "re-coat the CRT", will it work just as good? and how would I go about doing such a project when it comes to re-coating this CRT.

Thanks for your help guys, I think this set was in a garage for quite some time, perhaps the climate finally got to the coating, I have cleaned and examined three other sets I own and do not have this problem, maybe my luck has finally run out.

Jon

[Electronic M]

The coating is called aquadag and is some silver based material. Some have recoated their tubes with a product called aerodag (there was also another product who's name presently escapes me) with decent results. On tubes like yours where little of the material has flaked off I generally leave the tube be.

The process of recoating involves cleaning the old material off, masking EVERY where you don't want the spray coating to go, and then spraying it on. Note leave a large space (about 2-3") uncoated around the CRT anode button or arcing will ensue.

This coating is normally connected to ground, and it, the glass envelope of the CRT, and a similar coating on the inside form a capacitor which filters the HV supply.

[M3-SRT8]

Here's the stuff...

http://www.grainger.com/Grainger/SLI...ubricant-1WVK7

Works great. Make sure you mask off the anode area at least 4" diameter.

[bandersen]

Yes, it does work great. Here's a 10FP4 that was recoated with slip-plate by Hawkeye before they shutdown.