Hi guys. I have an outdated conventional mill at my shop. The servo drive board doesn't seem to work and I have no idea how these things work. There is no spare part or manual for the machine. It is a Maho MH600 and the company doesn't provide anymore spare parts for this antique.
Anyway:
Motor DC-Shunt Type:
190vdc shunt and field. 6 wire output. 2 wires tach, 2 wires field, 2 wires armature. 4,7amps and 0,33amps respectively for its traversing table. The motor thankfully only moves in 1 direction. It reverse and does its limits mechanically.
Problem:
On the boards output pins there are AB JK. When measuring JK I measure 200VDC. Pin AB has zero volts. I guess this is why the mill table won't move. I am not sure if JK is armature or field voltage? Maybe someone could answer this for me. AB is 2.5 ohms, JK is 800~900 ohms (i'll recheck this)
The board:
Pins AB and JK run to the board. Pins AB goes to two SCRs, and 2 big rectifier diodes. The capacitors were fried. I tried replacing them with their exact values. However the MP 0.1uF cap was replaced by a mylar 0.1uF rated at 250VAC (don't know if the type of cap is critical in this case). After replacing all components there was still no output voltage on Pin AB.
To be frank I have no idea or reference how this board should work. There should be a DC voltage on pins AB but it is only connected to two SCR and two diodes. How is it suppose to rectify AC to DC in this case? There are a couple of IC 8pin op-amps that I guess compares the reference to the tach and then will trigger the gate of SCR to vary the DC output? Am I mistaken? If so then why isn't the SCR triggering? Could someone provide a circuit example how this should work? Perhaps understanding the board better will give me more insight.
Special note:
There was a small box shapped capacitor with 6 pins which I desoldered which is connected somewhat to the Gate of the SCR (parallel). I desoldered it because I read 0 ohms/ 0 voltage drop between its pin and thought it isn't suppose to be shorted.
The part name for this cap is:
ZKB 407/043
-02-PF 213
Question: Does this mean 3x 250pF? I have no idea how to interpret this. I also cannot find this cap in local supply shops. Is this cap really necessary for the board to work?
The way I see it:
Maybe there are some products out there that can satisfy these criteria?
It needs the ffg specs:
- 190VDC shunt motor at least 6 amps. compatibility
- tach input
- Pot input for speed control
-220AC input
Any bright ideas where I could get such a driver board?
Some pics of the machine and circuit board
http://s747.photobucket.com/albums/xx117/olftdm/maho 600/
I need the following help if you can:
-Provide me any references how an SCR could work in a servo drive setup.
-Provide me more insight what these pins could mean.
-A turnkey solution. Perhaps a product that could fit into this category or as a retrofit
Crazy thoughts:
Maybe I should just plug 100VDC in pins AB (Bypassed) and see what happens? Maybe AB is the armature and JK the one that varries voltage?
Best Regards
Franz
Anyway:
Motor DC-Shunt Type:
190vdc shunt and field. 6 wire output. 2 wires tach, 2 wires field, 2 wires armature. 4,7amps and 0,33amps respectively for its traversing table. The motor thankfully only moves in 1 direction. It reverse and does its limits mechanically.
Problem:
On the boards output pins there are AB JK. When measuring JK I measure 200VDC. Pin AB has zero volts. I guess this is why the mill table won't move. I am not sure if JK is armature or field voltage? Maybe someone could answer this for me. AB is 2.5 ohms, JK is 800~900 ohms (i'll recheck this)
The board:
Pins AB and JK run to the board. Pins AB goes to two SCRs, and 2 big rectifier diodes. The capacitors were fried. I tried replacing them with their exact values. However the MP 0.1uF cap was replaced by a mylar 0.1uF rated at 250VAC (don't know if the type of cap is critical in this case). After replacing all components there was still no output voltage on Pin AB.
To be frank I have no idea or reference how this board should work. There should be a DC voltage on pins AB but it is only connected to two SCR and two diodes. How is it suppose to rectify AC to DC in this case? There are a couple of IC 8pin op-amps that I guess compares the reference to the tach and then will trigger the gate of SCR to vary the DC output? Am I mistaken? If so then why isn't the SCR triggering? Could someone provide a circuit example how this should work? Perhaps understanding the board better will give me more insight.
Special note:
There was a small box shapped capacitor with 6 pins which I desoldered which is connected somewhat to the Gate of the SCR (parallel). I desoldered it because I read 0 ohms/ 0 voltage drop between its pin and thought it isn't suppose to be shorted.
The part name for this cap is:
ZKB 407/043
-02-PF 213
Question: Does this mean 3x 250pF? I have no idea how to interpret this. I also cannot find this cap in local supply shops. Is this cap really necessary for the board to work?
The way I see it:
Maybe there are some products out there that can satisfy these criteria?
It needs the ffg specs:
- 190VDC shunt motor at least 6 amps. compatibility
- tach input
- Pot input for speed control
-220AC input
Any bright ideas where I could get such a driver board?
Some pics of the machine and circuit board
http://s747.photobucket.com/albums/xx117/olftdm/maho 600/
I need the following help if you can:
-Provide me any references how an SCR could work in a servo drive setup.
-Provide me more insight what these pins could mean.
-A turnkey solution. Perhaps a product that could fit into this category or as a retrofit
Crazy thoughts:
Maybe I should just plug 100VDC in pins AB (Bypassed) and see what happens? Maybe AB is the armature and JK the one that varries voltage?
Best Regards
Franz