Strange Orac problem

[PDodds]

Hi everyone.

I am new to the forum, and have joined on the advice of Graham from Denford.

I have a strange problem with my Orac which I would really appreciate some help with, as I am relatively new to them.

The machine has been working fine from me aquiring it 4 weeks ago.

Today however, when I powered it up, the relays seemed to be clicking more than normal, and the screen was flickering slightly.
I started the spindle in manual with no problems, and manually took one cut on my workpiece.
Then, the relays clicked again, the axes started to move themselves, and the spindle speed started to fluctuate erratically, at one point going exceptionally fast
There was then an unmistakeable electronic burning smell, and the screen went off completely.
I immediately switched the lathe off.
I tried switching it on again, and it powered up, but the screen still does not work. I can start the spindle, but it will not speed up, and none of the drives will move.
It is not past any of its limit switches.
I have checked all of the fuses that I can see at the back of the machine, and all are ok.
If I leave it powered on for a 15 seconds or so, one of the red LED's on the board to the left at the rear of the machine flashes erratically, and is accompanied by a relay clicking. I have attahed a picture to show which LED it is.

Any help would be very much appreciated. I am unfamiliar with the machines, but I am a competent mechanical/electrical engineer, so hopefully should be able to test anything suggested.

I am having a bad day, as I have had my Triac go down with an unknown error too.


Thanks
Paul

[Denford Admin]

I'd be looking for the cause of burning smell first.

ps please reduce the size of images before uploading - see this for some tips:
viewtopic.php?f=17&t=597

[PDodds]

I believe the smell to have been the back of the screen as there is visible scorching to it (and now it doesnt work).

I can start the spindle in manual, but not increase the speed. If I leave it for a few seconds, it suddenly ramps the speed up itself really fast, the slows down or stops, very errattic.
Neither of the slide axes will move in manual either.

Ps, I have reduced the pic size with the tool posted in your link - thankyou

[Denford Admin]

Where does the spindle command analogue come from on that machine ?
From what I've seen of an old starturn8 there is a seperate control board which I'm guessing takes a digital command signal from the CNC control and converts it to analogue command to the spindle drive. You may be able to fit a potentiometer to the spindle board and control the speed from there - at least then you know which bit is being erratic if it fixes the problem...

My guess is that the main control board is faulty as the drives aren't working either - check the voltages on test points (if there are any) and do the usual close inspection of relay contacts, solder joints, screw terminals, pin sockets etc etc

[PDodds]

Ok, I appear to have found the problem - I hope

I was fairly sure that the burning smell was coming from the CRT screen, so I pulled the connector plug on the circuit board which feeds the screen off, so that there was no power to it.

When I powered the machine back up, all axes now move, and the spindle is functioning correctly again.

I guess that either the screen/tube itself or the driver board had developed a fault, and was sending corrupt signals back to the main board????

Anyway, the machine now appears to be ok, other than I have no screen to see what is happening, so will try and source a new one.

Thanks for the help

Paul

[Denford Admin]

I think the blown screen was pulling the voltage down so that everything else was only half working.
There have been posts for CRT repairs and old CRT suppliers on here in the past if you look hard enough...

[angel-tech]

there is one on ebay atm.

[PDodds]

Hi,

I have seen the one on ebay, and will try to win it.

I think it is the board which supplies the screen which is at fault, as I removed the screen from it, then plugged the power back on to it and the problem was still there.

Is there any way to get the external monitor out to work without that board powered up?

Regards
Paul.

[angel-tech]

I have an Orac here to be converted so if all else fails i have one. I should have one from a previous conversion, but i can't guarantee it works.

[PDodds]

Thanks angel-tech, I really appreciate that

If I miss the one on ebay for whatever reason, I will give you a shout.

Ps, what is ionvolved in the conversion, presumably to Mach?

Is it a costly exersise?

Thanks again
Paul

[angel-tech]

The cost is negligeable, but it's not the easiest machine to convert, and yes, to Mach3