[wireb]

Just got done reversing the latest batch of Ebay TB6600 cards.
This one is marked BL-TB6600-V1.2 D412
Note in the photos the one without the heatsink I moved all the tall components to the back side so I can mount it to a larger heatsink assembly.
Attachment 330182
Attachment 330184
Attachment 330186

And the reversed schematic
Attachment 330188

The sort of good:
They used a 74HC123 retriggerable monostable multivibrator with a time constant of ~0.45s.
- When a pulse comes in (led on) it triggers the timer and drives the fet off and stays off till timer expires.
- When the pulse is done (led off) the driver steps and as long as the pulse is shorter than the timer it is still in full current mode.
- Every off to on transition of the led causes the timer to extend the timeout. Other than dropping power there is no way to get a runt timeout.
- This does not drive the TQ pin but rather puts a 10k resistor in parallel with the variable resistor. With the current setup this results in ~45% hold current at full range and ~55% at mid range. (may be an issue with small steppers with low current limits. But if that is the case pick a smaller driver.)
- Also this function can be disabled by turning SW4 off. Then the driver will run in full current mode all the time.

The Unknown:
Rosc is a 27k resistor. Data sheet recommends a 51k. Not sure what this would affect or if 27k is too low. (can anyone comment on this?)
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.)

The Bad:
1.) no thermal grease (seems like the norm. Also had one board with a missing screw that was broken off and another with the 470uF cap with one leg ripped out)
2.) Vref can exceed 1.95V (to fix replace R11 with a 31.6k resistor)
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 3.1A (to fix add a 0.47 ohm 1% 1W resistor in parallel with both banks of sense resistors will allow full 4.5A output)
5.) MO output overloaded (to fix remove the RUN led and replace with a 30.1k resistor)
6.) 5V reg overloaded (to partially fix remove the power led and add a 0.1uF cap from pin 24 to ground near pin 24)

I think that is everything on this board. Have one more board of a different design I need to trace out. Hopefully will have it's results yet this week.