[wireb]

Second card in this batch.
Marked MIB JY6600SW
Note I removed the heatsink before taking photos.
Attachment 330290
Attachment 330292
Attachment 330294

The sort of good:
Dual 6N137s on both step and dir.
Vref circuit correctly limits voltage to 0.3V to 1.95V ish.
Rosc in the valid rang (51k)

The unknown:
Enable is active (driver running) with no input. (could fix by rewiring the opto output but don't care about in my application as EPO takes out the motor supply.)
Power reduction circuit drives the TQ pin so output will always be either 100% or 30% with no disable switch. Could be modified to disable (tie TQ pin high) or change the ref point (for 50% reduced power use a 7.32k and another 2n7002 Nfet. see previous card design for rough hookup design)

The Bad:
1.) Heat sink glued on with an elastomer (may be heat sink compound may just be kitchen and bath) but was done tipped so large filled gap along one side.
2.) No filter cap on Vref (to fix add 0.1uF to line)
3.) AL output overloaded (to fix remove the AL led and replace with a 30.1k resistor)
4.) With Vref fixed max output is only 4.3A (to fix replace the 0.56 ohm resistors with 0.47 ohm 1% 1W resistors this will allow full 4.5A output)
5.) MO output floating (to fix add a 30.1k resistor from pin to +5V)
6.) 5V reg overloaded (to partially fix remove the power led, work led, lift U7 pin 3 and ground it, and add a 0.1uF cap from pin 24 to ground near pin 24)
7.) No filter cap on clock line (to fix add 100pF cap to line)
8.) Floating leftover gates in the 74VHCT14 (to fix tie the inputs of the unused gates to ground)
9.) Reset pin tied to power. (to fix lift pin and add a 12k resistor to +5V and a 0.1uF cap to ground)
10.) Missing filter caps on input power rail (to fix add two 0.1uF caps near the power pins of the TB6600)
11.) Missing input power protection diode (in theory not needed but be extra careful not to hook up backwards)
12.) Time constant of the reduce power circuit very short at 0.05s (to fix replace C1 with a 6.8uF cap and replace R19 with a 100k resistor to get a 0.68s TC)