[UkPaul]

Dear Members,

I'm hoping some of you might have a few pointers for a serious-ish problem I've run up against on my 1998 EZ-trak DX2. (2 axis version).

History as follows. Turned on yesterday, homed axes no problem, then while in jog mode and scrolling the y-axis, the axis 'coasted' to a stop about midway through travel. Screen showed 'axis drive fault' or similar. The table was not under load, or hitting anything. After resetting the error it then shows 'axes off' or similar, repeatedly.

Turning the machine off and on (with the back cabinet open) I see the following when switching on:

BMDC card initially red (as main screen counts down BMDC) then goes to flashing green. Axis drive boards both showing red and green light continuosly. When I clear the 'axes off' error on the main screen the red LEDs on the drive boards blink off VERY briefly, before coming on again, and the error 'axes off' redisplayed.

If I am gently turning the axis handles while resetting the error, a small 'kick' is felt from the axis motor, before the handle goes back to a free turning state (same behaviour on both axes). This leads me to believe that the cabling to the axes is ok. The co-ordinate readout on the main screen also counts fine when the handles are turned by hand (even before homing) leading me to believe the encoders are working fine too.

THEN, when leaving the machine overnight, and then switching back on, the machine appears to boot up fine, and both axis drive cards show single green LED, great! However, when I press '+' to home the axes, the screen just shows 'alarm' hit key to clear. Axis drive boards then revert to their mostly red-on behaviour.

I have checked as many fuses as I can find (fuses on the axis boards and also fuses in the cabinet, all fine).

I have checked as best I can for loose cabling etc. If the axis boards are showing LEDs, does this mean they are receiving main drive power, or are the LEDs powered from the data connection to the BMDC board?

My questions would be:

- If my y-axis card is fried, why do both axes have the 'red-led' error. Does the machine lock out both axes if one axis fails? I will replace the card or transistors optos if necessary, and would be comfortable with this, but I don't want to start replacing things at random with blind hope.

- Is there any way I can test the axes individually electrically, or by swapping cards? Or is there any diagnostic or DOS mode where I can try to move or test the axes individually?

I'm willing to put the time and effort in to fix it. I really need to try and fix it within a week.

Any help very much appreciated.

Many thanks - Paul

[machintek]

If this is not a CIB (control in a box machine), you should have a AUXBOB board on the bottom of the cabinet. It has only one green connector. Pull it and it removes 12VDC from the drives and enables them. One drive will have the RED LED ON. This is the axis that has the fault. Swap the drives (turn machine off first) and see if the fault follows the drive board (fault is the board) or stays with the same slot (fault can be motor or cable).

George

[UkPaul]

Great! Thanks a lot for the reply, very useful. I am going to try that in a few hours time when I get home tonight.

If I am able to identify that I have a faulty drive board, what are my options for repair? I am based in the Uk, and the high expense and time of a refurbished 'swap-out' board from the US is not really viable.

I'm thinking of having a go at repairing the board myself. I am comfortable with electronics, but wondering what are likely failures. I am thinking output transistors, and also I have heard it mentioned that the optos can go?

Thanks - Paul

[UkPaul]

Update, making progress!

I unplugged the green connector from the AUXBOB as you suggested - thanks George. Indeed one of the red lights extinguished! I then swapped the axis cards, and the fault followed the axis card, rather than the axis. So, probably a faulty axis card. Then I removed the card entirely, and looked at output transistors. 2x IRFP250N and 4x IRFP9240 Mosfets. Best of all, these are still easily available from electronics catalogue. A full set + postage cost me around $60 and I should get these in the next day or two. I am taking quite a big gamble that the fault is actually the MOSFETS, but it is worth a shot. None of the MOSFETs are structurally damaged (and I've heard they often fail catastrophically), so that isn't great.

My axis boards are 'Motion Science Inc' 9230031-QC Rev C.

Does anyone have any experience of such boards failing, and do I have a reasonable chance of a fix by changing the MOSFETs. Any other typical failure modes?

Anyway, getting there hopefully!

Thanks : ) - Paul

[UkPaul]

Another update, not making such good progress anymore...

I have checked all the existing MOSFETs on the board, and they all appear to be intact and working. I have carefully tested them with a multimeter and coin cell to turn them on and off, and they all appear to work. Have also checked a fair few of the diodes and resistors, all seem ok.

There are two optos on the board a 'H11A1' and a '4N32'. Both 6 pin devices. Does anyone know what function these perform, and how/why they fail? I don't know if mine are good or failed.

My board is a 'Motion Science' bridgeport part number '3154-2529'

also here.

BptParts.com: Bridgeport Machine & CNC Machine Replacement Parts

Big $$$ and international delivery time, taxes, so very much trying to avoid that option...

Does anyone know much about repairing or troubleshooting these boards?

Oh well, starting to run out of options, but tips gratefully received.

thanks - Paul