I recently acquired a Haoyu TB6600 drive and thought some might find the following write-up of interest.

Looks can be deceiving but this little drive does get a number of things right.

For a start the board is well assembled, only its hand soldered connectors and opto isolators are covered in messy flux residue.

Unlike the TB6560 boards, this implementation gets the opto isolation right...well almost.
The step and dir pins use fast 6N137 opto isolators with a slow PC817 on the enable pin.
The error is that the drive defaults to always enabled at power-up. A current must pass through
the enable opto isolator to shut the drive off. I'd rather the reverse situation apply.
There are two spare inverters on the board and one could be used to correct the phase of the enable signal.

The motor step occurs at the very instance when current is made to stop flowing in the step opto isiolator.

The tab of the TB6600 is isolated from 0V allowing the chip/heatsink to be bolted directly onto the case chassis or
more TB6600 attached to the same heatsink without fear of motor currents flowing in the chassis.

The connectors are the weakest link IMO. I'd much rather a simple screw terminal than incur the extra contact surfaces.
The weakest is the 2 pin power connection. I would not wiggle the 4 pin motor connection when operating, for that is
sure to destroy the drive.

There are very short and direct PCB traces from the drive to the A+/A- and B+/B- motor phases made possible
by the engineers at Toshiba adopting an easier to route device pinout.

The sense resistors do not look to be the low inductive current sensing type but there are 3 of them per phase.
What ever the value, the total inductance it is at least a third that of any one resistor.

I very much doubt if the bulk capacitance on board is the low esr type. This could be a point
of failure when the electrolytic dries out, but is easily rectified by replacing.

There's no decoupling caps close to the +Vm pins of the TB6600 but it only took a few minutes to get some fitted.

When mounting the heatsink, one of the holes is blocked by the connector.

The PCB mounting holes are symmetrical and the board can be rotated 180 deg to make air flow/wiring easier.

The switching frequency was measured to be 40kHz.

In the absence of step pulses the phase current is reduced.

I kept motor wiring neat and tidy, and took full advantage of the opto isolation to keep motor currents isolated from the chassis and
opto drive signals. There was 7ft of 16AWG/4 between the drive and motor and 10ft of CAT5 cable from the
drive to the BOB, the drive was set for half stepping, the motor was in-situ on the mill and operating at 2.5A, +Vm was 27V.
There was no missing steps nor any motor hissing or squeals. The motor had plenty of torque.

Given the choice I much rather this drive over ANY TB6560 design.