a real challange?

[Kevin Kuehn]

Originally Posted by Yamamaya42

Looking closer at the data for the 6AT6, it seems that it IS being used for something in the set.

The tube is... a “Duplex-Diode High-Mu Triode”
The diode part is being used for something, but not sure what, or how, it goes down to the contrast control, and to the tuner ( not shown on sams schematic, but I can see the wire in photo page 6 0074-3 )

not really sure what this does however

Good eye, I missed that. Those two diode plates share a common cathode with the triode section. It appears to me they are using the forward bias of those diodes as a voltage reference for the Picture(Contrast)control. That variable voltage is feed to the grids of rf and if tubes, which in turn varies the gain of those stages. Unless I'm missing something I don't believe the set has any automatic gain control, only that manual picture adjustment.

[Kevin Kuehn]

They do show the same thing in Sams 74-3. It's just a little harder to follow because Sams doesn't label the b+ and b- supplies very well.

[Yamamaya42]

Originally Posted by Kevin Kuehn

They do show the same thing in Sams 74-3. It's just a little harder to follow because Sams doesn't label the b+ and b- supplies very well.

Main difference I see, ( prob does not matter, but is confusing :/ )
on SAMS 0074-3 tuner section, rf amp area v1, r11,r10, c9, point where the 3 meet goes to r12
(1k) then gnd.

on other schematic (895 ) same area,
r13 r3 ( r11,r10 above ) , c5 ( c9 above ) this is hooked up the same as shown in the SAMS,
however after that it's different, r12 (same as above ) the 1k resistor does NOT tie to gnd, but to a green shielded wire, back to that contrast / picture control circuit.


Which is what is weird, cause before you sent your scans, I was looking and looking, wondering WTH that green wire was, cause I could see it on my set, I could also see it in the underside photos in 0074-3, but could not work out what it was doing going to the tuner, till now.

But who ever said SAMS were 100% accurate? :p