Collins 26U schematic questions

[gary o]

http://www.collinsradio.org/html/manuals.html

26U is near bottom of the page also 26J is similar limiter

Im currently soldering the front end of the Collins 26U together RE my other post....here

http://www.groupdiy.com/index.php?topic=26900

Im wondering about the resistors around the cathodes of 6386 I wpold have thought R4 & 5 would have been same values ?
Are they coz of R7 & or R6 ?
Also why such precise value 90.9 Ohms .... R6 ?? not seen this in similar limiters
Also R8 & R9....... 5110 ? on schematic ...parts list in manual says 1 Meg ?

The 26J limiter( same as 356E-1 Im told) I read is same but without interstage tran

Has different values resitors around front end ?

Sorry for questions but tryin to understand....sadly Im not too hot on some basic electronics, spose that doesnt help but thanks for reading

 

[PRR]

> I wpold have thought R4 & 5 would have been same values ?

R4 196 goes to ground.

R5 90.9 reaches ground through 121||1K. Which is 107.939. 90.9+107.939= 198.8 ohms which is equal to 196 ohms (almost).

> why such precise value 90.9 Ohms

1% resistors were often marked with odd values to make it harder to accidentally put a 10% resistor in.

> R8 & R9....... 5110 ? on schematic ...parts list in manual says 1 Meg ?

5K makes sense. Then R10 1K pot gives +/-10% adjustment for tube balance. 1Meg does not make sense. I think you caught a typo.

> The 26J limiter... same but without interstage tran

Lacks booster between VCA stage power stage, lacks time constant controls, lacks regulated VCA power.

26J is smaller/cheaper for utility work. 26U is the monster you use at transmitter or disk-cutter.

 

[emrr]

M used to mean K; been covered before.

26J sold as automatic gain control / compressor. l
Low ratio. 26U sold as limiter; high ratio. Same deal as StaLevel driving SA-39.

 

[gary o]

Hi PRR & doug thanks for great info resistors PRR near cathode make sense now thanks doug R8/( 5110) in parts list in manual says they are 1000 000 ohms ...seems like typo ...

I love reading about vari mu units ...thanks once again