Pictures by https://github.com/Floppie209/Amiga2000-remake
⚓ Buffer Fix
“Better video picture”
⚓ Remove RP900 and RP901
CPU is in the middle, the two resistor pack have been bent to break them, effectively removing them.
⚓ U603 & U604, solder pullup
pin 1 network to pin 10 IC
pin 1-9 (or 2-9) network at pin 1-9 (or 2-9) IC
makes them closer to IC than CPU.
⚓ res pullup RP903 & RP908 (3.3kohm)
replace (with ?) 1kohm or connect pin 36 of U800 to +5V via 1kohm
only needed if the 74ALS245 right next to it is branded from Signetics.
BUT in two board with no Signetics it was in place… and RP903 and 908 were 1kohm.
⚓ solder resistor betweenm pins 11 and 20 of U605
no idea, not present on my rev 6.2 or another one
⚓ Various Fixes
⚓ Remove left connector from R215 and solder to left side of C215
“Solves Molly problem”
It connects R215 to +5V_USER instead of EMI200 which goes to +5V.
⚓ Solder 68 ohms and 270 pF series to the far right of the 4 vias below CN303, ground the other end of the circuit
“Eliminates switching guru”
Tied E from CPU to GND through C and R.
⚓ Install voltage monitor (PST518B, Mitsumi) instead of D802. Pin 1 at cathode D802, pin 2 at ground, pin 3 at anode D802
The pin 3 is under the body, on the same level as the others pins of the components on left and right
“Eliminates turbo cards shutdown problem”
⚓ Remove capacitor C909
Problem solved : unknown
It seems that this .1uF is used to avoid triggering a reset on short pulses (noise…), but some generated by the CPU gets eaten by it.
Might be useful to remove if getting issues I guess.
Between U300 and U301, was STILL present on my 6.2 and another one, probably not a fix applied finally.