“Slash used #36 to record AFD, not #39… The mod on #36 have been made by Frank Levi and it was based on the #39 1959T Super Tremolo Mod made by Tim Caswell.
#36 is a Standard 1959 Superlead with an extra pre-amp gain stage. An additional (fourth) preamp tube was mounted in a hole drilled next to the original (three) pre-amp tubes.
#39 have a switch to turn the mod on and off, #36 don’t have that switch, the Mod is always “on”.
According to a post on the LP Forum, the usual Frank Levi Mod is :
Input jack to first stage – 34k resistance (the two stock 68k’s in parallel), or a 33k will do.
First stage cathode – 3.3k bypassed with 330mfd.
Out from first stage, through .022 into a 1 meg pot. Bypass the pot with a .001 cap. Out from pot through 470k bypassed with a 570p cap, on to second stage.
Second stage cathode – 2.7k bypassed by .68mfd (you’ll notice this is the stock 1st stage values – you can save some time/trouble by just switching the wires on the first two stages).
Out from 2nd stage, through .022, into 1 meg pot (use one of the now extraneous input jack holes). Bypass pot with a .005. Out from pot through a 470k bypassed with a 500p, on to third stage.
Third stage cathode – 3.3k bypassed by a 330mfd.
Change tone circuit cap from 500p to 250p.
Everything else – leave as stock.”