What have I done!

[Clive S]

I have a Heiz High Z 1000T which I use daily and it has proved as solid as a rock for the last 6 years. I was getting fed up replacing the Kress spindle every year so I have started to convert over to a water cooled VFD. Wanted to add a no voltage contacts for switching the VFD (DCM+FOR) so I thought the neatest way would be to add a 12v relay with volt-free contacts inside the controller and piggy back the 12v relay that switches the existing 240VAC supply to the Kress, which would then be left redundant but still there if I needed it. Simples, I thought & now the trouble has started

I have now removed my additional relay to try and get the machine to work again, though I think something else must have been upset. Is was the PSU board that I had removed and took lots of photos to ensure that the leads were reconnected correctly. What is happening now is when the controller is connected to the steppers and powered up, everything seems normal and the steppers are holding. When I connect the 25pin PP cable to the PC port and powered up, the steppers all make a horrible noise and are creeping slightly. It does this only when connected to the port of the PC (any PC in fact as I tested it with my backup PC) but it is fine when the 25pin cable is just connected at the controller end. Does anyone have any ideas please as this is now way beyond me.



The rough rectifier mod at the top of the photo was made years ago, after the solder kept melting on the diodes of the rectifier OP, but that has been faultless since.

Many thanks in advance,

Gavin

Ok then where are the lots of photos? Can you be more specific in what is wrong? Do you have a schematic?

[artmin]

I have found the controller schematics here: http://www.cnc-router-store.com/wp-c...trolhy_eng.pdf

The voltages all seem good at the 5V 12V +37V outputs, though the 37V is reading 33.5V

What I have discovered is if I shake the PC end of the PP cable in the air, some of the axis move. When plugged into the computer (off & on) the motors are squealing and the controller relays for the spindle & coolant are buzzing, sometimes. When I remove the jumper wire from the controller back to the relays on the power board they stop okay so seem to be getting a pulsing signal from the computer end. When the PP cable is disconnected from the computer the motors are fine.

I delved into the PC and I couldn't find the PP card in the device manager and pulling it out & replacing it with a boot in between, it's not recognising it. So I plugged into the onboard PP and changed the port address and the motors at least appeared to be responding to the jog controls, though not moving (pitch can in the sound). The sleep function appears to be working too.

I swapped over to my spare pc which only has an onboard PP and I could get the axes to move roughly in the right direction, but with lots of noise & judder. They motors still squeal when stationary whether or not the PC is powered up.

I have just ordered a new 25pin card & cable as a starting point. Does this sound like an issue with the PC now or do you still think that it could be controller related. I have checked for anything that could short out the control boards and all look clear. I gave it a light blast with the airline too.

[Robin Hewitt]

I usually get completely the wrong end of the stick but let's have a go.

If you fitted a relay and everything went wrong even after that relay was removed...

This would suggest the relay had no protection diode and what ever you were using to drive the relay also drove the thing that no longer works.

You probably know about protection diodes but just in case. Current flows through the relay coil. A semiconductor device attempts to break the electrical circuit. The coil inductance requires that the current continues to flow, the volts go through the roof, the break down voltage of the semiconductor is exceeded and the magic smoke escapes. A protection diode across the relay coil allows the current to flow back through the coil until it dissipates.

[artmin]

Thanks Robin, never heard of protection diodes but there is a diode beside each relay on the power board:



I had taken leads from the coil pins of the existing relay on the underside of the power board to supply my additional relay. Maybe this extra load could overload the circuit, but the relays are still working okay using the manual override switches on the front panel. I didn't notice or smell any smoke at any point. Saying that I was flapping around at this point. Can't see any burn't components anywhere.

[artmin]

Quick question. Does the 25pin port from the PC supply the 5V signals towards the controller only, or does the controller also have to send 5V signals back to the PC. I know that limit switches at least have to send a signal back in some form.

[cropwell]

The PP pins send and receive 5v signals depending on the pin. What worries me about this controller is that it has no opto isolation and so your computer is vulnerable. You should be glad that you have a PP card as it is easier to replace than a motherboard. Everything points to a spike going back to the PP. The pinout diagram shows the capabilities of each pin. How they are used depends on the controller. If it were my controller, I would replace the driver board with a BoB and three drivers, but it is a lot of work to cure what could be a simple fault.

[artmin]

Thanks for that, I am hoping that it is just the PP card. Hopefully I will receive a new one by Tuesday. I remember when I could have popped over to PC world and picked one off the shelf but times seem to have changed.

Replacing with a bob and drivers is my backup plan if all else fails. It is exactly as you put it so well: A lot of work over possibly over a simple fault. If I did end up going that way, with 2 steppers on the X axis, could I get away with 3 drivers or would I need 4?

Cheers,

Gavin

[magicniner]

+1 on the voltage spike possibility

The PP pins send and receive 5v signals depending on the pin.

Or 3.3V for most modern cards and laptops.....

I remember when I could have popped over to PC world and picked one off the shelf but times seem to have changed.

Maplin still stock some but I'm not sure what bus types for and what voltage data levels.

- Nick