Anyone have a schematic for early 60's Zenith with peak picture control?

[kramden66]

Was wondering , i'd like to see a schematic for one of those zenith sets that had peak picture , it was found on the 23" consoles early to late 60's sets had them the 19" table sets didn't

thanks
mike

[David Roper]

Is that for switching DC restoration in or out?

[dieseljeep]

Originally Posted by kramden66

Was wondering , i'd like to see a schematic for one of those zenith sets that had peak picture , it was found on the 23" consoles early to late 60's sets had them the 19" table sets didn't

thanks
mike

Their higher end B/W portables had it as well. Also known as a "Sharpness" control.

[old_tv_nut]

Originally Posted by David Roper

Is that for switching DC restoration in or out?

I don't think any set ever had a switch to turn DC restoration on and off. Designs had a certain amount of DC restoration (or lack of it), and that was that.

[David Roper]

Do you want to put money on it?

[old_tv_nut]

Originally Posted by David Roper

Do you want to put money on it?

Nope - what is the example (if it exists, I'm guessing it's a monitor rather than a consumer set)?

[kramden66]

wow all this because all I asked was if anyone had a schematic , probably from a sams for an early to mid 60's zenith 23" set with peak picture which is aka sharpness

B y the way anyone have one ?

mike

[Kamakiri]

My 23" Zenith is an F2737E, from 1961 (23ZP4 picture tube). It doesn't have a "peak picture" control that I can see, but it does have a "quad coil" adjustment. To this day I have no idea what that does.

I don't have the schematic for it, but at least now you've got a model number.

[earlyfilm]

Originally Posted by Kamakiri

. . . . it does have a "quad coil" adjustment. To this day I have no idea what that does.

The quadrature coil is Zenith's name for a resonant coil, that is tuned slightly offset from the FM carrier, and is used to detect the FM sound modulation instead of the more common ratio detector.

Jas.

[old_coot88]

Minor quibble, but the quad adjustment is peaked on the center frequency, not offset as in slope detection.
As the tube ages, sometimes you have to re-peak the quad coil and "buzz" pot for best sound.
Excellent tutorial on gated-beam detectors here..
http://www.tpub.com/neets/book12/51e.htm

Since the tube (usually 6BN6) plate is supplied from B Boost, the detected audio is high level and drives the output stage directly. Completely eliminates need for a 1st audio stage.

[Tubejunke]

Somewhere at home I have schematics for a few varieties of the same chassis that Zenith used for what looks to be a fair amount of years. Mine was a 58 or 59, but I found the same chassis going well up into the 60s with only minor changes. Seems like that 6BN6 was a keeper for Zenith engineers.

[earlyfilm]

Originally Posted by old_coot88

Minor quibble, but the quad adjustment is peaked on the center frequency, not offset as in slope detection.

You are absolutely correct!

I was remembering the adjustment procedure on these babies and not how they worked.

Most times after changing the detector tube, these needed to be tweaked for least distortion at best volume after the set warmed up. This means if you were replacing this tube in the field, you had to a wait a while before you could finish, especially in damp weather.

This was a given on these circuits, but I can only remember having to align a ratio detector (you don't just tweak those), when some component other than the tube failed.
Jas.