Originally Posted by
H.O
Hi guys, and welcome back Kreutz!
After experiencing the exact same as Jozsi did, where the motor was stiff in one direction and sluggish in the other I replaced U9 since that fixed Jozsi's drive up. However, mine is still behaving strange.
Background:
Replaced C28 with 4.7uF/25V tantalum cap.
Replaced R54 with jumper wire
Placed 1N4148 between R54 and GND, cathode facing GND
Replaced R21 with 4.7k resistor.
Ref1 voltage measures to 2.96V, Vref set to 80mV, VrefOC measures to 180mV.
1) 60V powersupply, everything seems normal, motor feels and sounds the same in both direction - slow limit LED does not come on, no matter what though.
2) 90V powersupply, motor stiff in one direction sluggish in the other, slow limit LED never comes on. Vpp across sense resistor seems to match VrefOC when turning the shaft one directiona and Vref when the turning the shaft in the other direction - VERY noicy though.
3) 120V powersupply, motor stiff in one direction sluggish in the other, slow limit LED never comes on. Measurements as with 90V supply.
4) Backing off the powersupply voltage to around 60V and it's back to "normal" again. That is peak-current all the time.
I've desoldered and checked the Schotky diode and I've replaced U9 a second time but the results are exactly the same.
All ideas appreciated!
/Henrik.