Zenith and degauss (and also HV regulation)

[nasadowsk]

After vacuuming the floor in here while waiting for my shirts to dry (Yay single male life!), i was wondering:

When did Zenith get auto degauss? I know RCA had it with CTC 16x. Did any Zenith roundies have it?

And also, when did Zenith start using pulse regulators in lieu of the ever-popular 6BK4? And naturally, did any of their roundies use it?

Bonus thought- does anyone know the logic behind the wacky power rectifiers used in their first color chassis?

[old_coot88]

If by 'wacky power rectifiers' you're referrin' to the dual 3DG4s (3DG4 is sort of a 'hunkified' 5U4 with different basing), Zenith probably considered them more robust and reliable than Si diodes of the time. That'd be my guess.

[Jeffhs]

Originally Posted by old_coot88

If by 'wacky power rectifiers' you're referrin' to the dual 3DG4s (3DG4 is sort of a 'hunkified' 5U4 with different basing), Zenith probably considered them more robust and reliable than Si diodes of the time. That'd be my guess.

Some Zenith TVs of the late '50s-'60s used one 3DG4 as a low-voltage rectifier, but I've never seen a Zenith with two of these tubes in parallel. I once owned a 23" Zenith b&w console which used only one 3DG4 in the LV power supply. The only reason Zenith would have designed a TV to use two of these tubes, IMHO, would be if the TV were a 3-way console, with a record changer, AM-FM stereo radio, and a very powerful audio system (as most of the combo Zeniths probably had). I cannot see the sense or reasoning in using two rectifier tubes for just the television chassis.

BTW, aside from the Zenith TV I had, I've never seen any other TV (Zenith or any other make) which used the 3DG4 as a LV rectifier. As I said, I think the reason Zenith designed some of its TVs with two LV rectifiers may have been to handle the additional current requirements of sets with powerful audio stages, such as their 3-way TV-phono-radio consoles. The use of two 3DG4s in the LV supply of any kind of TV other than a 3-way console, IMHO, would be overkill; after all, why on earth would a TV, and just the television (no record changer or radio) draw so much power as to require two LV rectifier tubes?

[Electronic M]

Originally Posted by nasadowsk

After vacuuming the floor in here while waiting for my shirts to dry (Yay single male life!), i was wondering:

When did Zenith get auto degauss? I know RCA had it with CTC 16x. Did any Zenith roundies have it?

And also, when did Zenith start using pulse regulators in lieu of the ever-popular 6BK4? And naturally, did any of their roundies use it?

Bonus thought- does anyone know the logic behind the wacky power rectifiers used in their first color chassis?

I know Zenith had the auto degaussing in M line and N line roundys...My old L line didn't have it, but I forget if the schematic showed it as optional.

Zenith stopped roundys at N line and those still used 6BK4s for regulation...I think the N line rectangular sets used the old 6BK4 shunt reg too. The pulse regulator was rectangular only AFAIK.
The oldest pulse regulator Zenith I have is a Y line (1968).

Zenith's first color set the 29JC20 did use 2 3DG4s...IIRC the power consumption is around 500W and I remember when one of the rectifiers got gassy and started arcing over internally, pulling it and watching the other shortly start doing the same from being overloaded...
I eventually found 2 healthy ones in my bins and that made it happy again.