CRT Boosters and CRT Booster/Isolaters

Back when sets had CRT's, especially up into the 70's, CRT replacement was not cheap. To replace a CRT with a new one could run from about $50.00-400.00+ in 70's money, depending if it was B&W or Color.

 As emission of the CRT dropped  in B&W CRT's the picture could become "silvery" or really washed out. In color, the color could be really weak in one gun or it wouldn't track with the other guns.

Enter the CRT Booster for B&W TV
 Basically it was a small transformer with a 6.3V primary and a secondary that  (In some cases was adjustable) up to appx. 8-10V.
 Some were auto-transformers and some were isolated secondary windings.
 Boosting the filament voltage would increase the emission, thereby bringing back the picture to a watchable level in most cases.

 In theory, this would shorten the life of the CRT, but what did you have to lose? $2.95 for a booster, or $50+ for a CRT, plus the labor to install it.

They made boosters in many types. For B&W & Color in series and parallel filament configurations. (Last I remembered, there were 28 different types made by just one company alone!). Many had to be tailored for a specific CRT's requirements.

They also made isolation transformer and isolation boosters for CRT's with Heater to Cathode shorts. Sometimes you didn't need the boost, bust the isolation. Some had a switch built in for 'series or parallel" filament.

Some were pretty large for the early color CRT's and some of the latter I bought were literally potted in the end cap of PVC pipe. 
(I used a lot of these on the imported CRT's.)

Now you ask, could you boost a booster?
 Yes, you could.
 I myself have seen as many as 3 plugged together in series, but one shop back East had reported they found 11 - YES ELEVEN! in series.
 (That set owner sure drug every particle of emission they could out of that poor old set!  ).