Questions about a CRT Brightener

[Chris K]

Good day fellow vintage TV lovers!

I have a TV with a 12LP4 that could use a little help. I bought a NOS brightener made by the Vidaire company. Probably from the mid 1950s. I have a few questions for the experts since I know little other than they boost the filament voltage about a volt.

1. Since this is a 75 year old item, is there anything I need to do to prepare it for use i.e. install it on the TV and bring the unit up slowly on a dim bulb or my Sencore isolation transformer Variac?

2. It has a "Series/Parallel" switch on it. I know about series install but what happens with a parallel install?

3. It's heavier than I expected. What's in this thing?

4. What modification can I do to the TV to achieve the same result as installing a brightener? Is there a way to put a potentiometer in this modification if I find I only want 0.5V boost or if I want to risk a bit more than the brightener would do?

Thanks everyone!

[N2IXK]

1. Since this is a 75 year old item, is there anything I need to do to prepare it for use i.e. install it on the TV and bring the unit up slowly on a dim bulb or my Sencore isolation transformer Variac?

Should be good to go right out of the box, as long as all the wiring looks good.

2. It has a "Series/Parallel" switch on it. I know about series install but what happens with a parallel install?

You set the switch according to whether the set has series or parallel wired filaments. If most of the tubes in the set have type numbers beginning with "6" and you have a big power transformer in the set, then you have a parallel setup. If there are a bunch of different numbers on the tubes, and no power transformer, it is likely a series filament set.

3. It's heavier than I expected. What's in this thing?

A small iron-core step-up transformer.

4. What modification can I do to the TV to achieve the same result as installing a brightener? Is there a way to put a potentiometer in this modification if I find I only want 0.5V boost or if I want to risk a bit more than the brightener would do?

You could maybe add a series resistor to cut down the amount of boost given. No easy to add additional boost other than adding a second brightener, which isn't recommended.

[Electronic M]

A second brightener usually reduces the voltage. The additional load the second one makes loads down the first.

[zeno]

A few more : Gently pry the socket off. If you just yank it odds
are it will tear the socket out of the CRT.
Brightener will boost to @ 8 VAC.
After the sets been run a few days try removing it. They do wake up CRT's
sometimes.
Rejuvenation only other choice. Can be risky.
BTW after @ 1980 a different type brightener was made & they dont
interchange !Those sets used 15,750 Cycles, the old ones 60 CPS.

Zeno

[Chris K]

Thanks guys. Actually I didn’t mean adding a second brightener. I meant in lieu of putting one on would there be a way to modify the chassis to make the filament voltage to the CRT variable so I could set it a little higher or up to the edge of disaster if I chose to do so. Unfortunately I’ve never had an original to the chassis or replacement 12LP4 that’s been close to strong. In my Dumont Chatham Doghouse I obtained a strong 12QP4 and swapped out the original 12LP4 with that.

[Electronic M]

If it's a Dumont RA-103 doghouse then it's parallel heater.

On a parallel heater set you can run the CRT heater through a voltage doubler circuit (couple of 220uF 25V caps and a pair of 1N400x diodes) which will make around 12.6VDC from 6.3VAC (CRT heater shouldn't care if it's being fed DC) then you can use a LM317 or LM337 (and a pair of resistors to set its output voltage) to regulate that anywhere from 1.37V up to 12.6V...You can even use a pot to adjust the level on the fly.