I wired the drive separately (the 3 phase power supply) and removed the belt that link the motor to the gearbox (the machine's gearbox is empty, I'm waiting for oil to fill it). Isolation seems good (I don't have a megger), collector and brushes are in nice shape on the motor and the tacho. I measured 2,1 ohms for the armature, 214 ohms for the field, around 300 ohms for the tacho. Here are the data of the drive and spindle motor: Then entered an M03 S200 in the controller, the spindle started to move, everything was normal but when I asked for S1000, nothing would happen, I guessed the drive needed some tuning. I didn't look very deep into it because I had a spare drive on a shelf (the exact same model, I got it from a scraped machine some times ago), I set the potentiometers with the same values as the drive I was removing, wired everything. I started to repair it 2 weeks ago, the Heidenhain controller works fine, axis move, but when I've tried to have the spindle runing, the spindle drive made a terrible noise and the motor turned very very slowly, I guess there's something wrong with the thyristors or their firing logic. The machine is an Hermle UWF851 (Deckel type of the 80's), with a TNC155 controller, it wasn't working when I bought it last year, the seller told me that the spindle motor 'probably didn't get a signal'. I'm having a problem with the Siemens spindle drive of a machine I'm trying to repair, and I'm really running out of ideas, thank you for taking the time to have a look at it. It's been a while since I've been on the forum, sorry about that.

Deskcnc controller board