Federal AM-864 / CA-1589 Mod List

[slor]

I am about to dig into a stack of three CA-1589s and I've been collating through the recommended mods and fixes. In the interest of sharing what I've read (and getting needed insights from Those More Knowledgable), here are what seem to be the most    common mods. Please feel free to pipe in with correction, corroboration, etc.

    -Add a 30dB “U” or "H" pad before 600 Ohm input

    -Disconnect jumpers for LO 600 Ohm input

    -Place a 680 Ohm resistor across output terminals

    -Add variable attack and release controls. "Attack" replaces R1/R-21 (AM-864/CA-1589) with a +/- 50K linear pot in series with  a +/- 22K resistor. "Release" adds a +/- 2M linear pot in series with a +/- 200k resistor, both in parallel with C1/C-5 (AM-864/CA-    1589). 
 
    -Change the coupling caps between the 12AX7 and 12AU7 to 0.0022 versus stock 0.001

    -Add 1 mfd of filtering at the B+ branch point that supplies the 12AX7 and the 6AU6's

    -Replace input 500K linear pots with a dual 50K log

    -Add anode balance: 100k or 250k 1W linear taper pot between R3 and R4/R7 and R8 (AM-864/CA-1589)

Again, I'd love to hear from anyone with real-world experience with these units. Thanks in advance!

 

[mjrippe]

To avoid confusion, make two threads - one for the AM-864 and one for the CA-1589.  They are quite different circuits in many ways.

 

[emrr]

Or use existing threads that already have the info.  We're all too lazy to know or care where we already talked about things years ago.