Compiled a listing of Zenith vertical RC networks

[wa2ise]

Found a bunch of Sam's, and went thru them to see what I could find out on those 3 legged RC network modules they liked to use in the vertical circuits.

Zenith RC circuit network modules:

PHP Code:

Zenith part    R, C discription
87-4        68K, 0.0024uF distributed over the resistor body
87-5        90K, 0.0024uF distributed over the resistor body
87-1... R= 57-64K... C=.006-.0065
87-10... R=70-83K... C=.0022

87-8
               in---+-68K--+--68K--+--out
                    |      |       |
                  680p    680p   680p
                    |      |       |
                   gnd----gnd-----gnd

87-7            in--+-82K--+--82K--+--out
                    |      |       |
                  680p    680p   680p
                    |      |       |
                   gnd----gnd-----gnd

87-4            in--+-33K--+--33K--+--out
                    |      |       |
                  680p    680p   680p
                    |      |       |
                   gnd----gnd-----gnd

87-5            in--+-47K--+--47K--+--out
                    |      |       |
                  680p    680p   680p
                    |      |       |
                   gnd----gnd-----gnd 


Also found the Sam's for the RCA CTC4 color TV

[jeyurkon]

Thanks for sharing.

[bandersen]

Interesting. Anyone know how they distributed the capacitor across a resistor ? Maybe a metal film surrounding the resistor ?

[wa2ise]

Originally Posted by bandersen

Interesting. Anyone know how they distributed the capacitor across a resistor ? Maybe a metal film surrounding the resistor ?

Most likely the resistor element is "printed" on one side of a ceramic disc, and the capacitor part deposited on the other side of the disc. That what the Zenith RC module physically looks like without cracking it open...

But it looks like the 2 resistor 3 cap circuit was also described as as a working substitute for the Zenith RC module. Looks like they divide the resistor by 2 and the cap by 3 to get the substitute parts values. Doing 4 and 5 probably gets you closer yet, but 2 and 3 is good enough.

[cwmoser]

Why did Zenith choose a "hybrid component"? Was there an Electronic need for this or was it simply cost saving? Has anyone substituted discrete components as a replacement - how well did it function?

[PaulOF]

The Sams' folder for the zenith 24h20 chassis shows the lower network in the sketch as an alternative to the upper one.
scheme2.JPG
Used it in my porthole and it seems to work fine. The diode needs to be germanium.
Paul