Electronic problem on MAHO 600 / TNC 135

A friend of mine has a MAHO MH 600 P fitted with an Heidenhain TNC 135 control.

When he puts the machine under power, the hydraulic pump is the sole thing to work. There's no more input through the keyboard except for the emergency stop. Nothing else work, neither spindle nor feed.

The screen shows weird signs and says "program memory defect"

He tells me that the problem first occured with a move on the z axis, that wouldn't stop. The the machine ran the table with the rapids in every directions before my friend hit the emergency stop.

And since then, nothing but the fore mentionned message.

I ask you the question in his name just because he doesn't feel comfortable with english when it comes to machinery...

Any input, things to check ?

Machine is a 1983 MAHO MH 600P

I've never had the H135 control, but has he checked the obvious already...loss of parameters ? If the machine has sat for some time without use the backup battery could have got weak enough to loose parameters.

The Z axis running amock could happen if the machine still had most parameters but had not lost all of them just yet.

Could also be something more serious of course...EPROM gone bad, all sorts of things.

Do you have easy access to that backup battery on Heidenhain controls (generally speaking), or is it a proprietary or hidden battery or something like that ?

Excuse me if my questions seem dumb, but I've never opened a control (not even a DRO), so be gentle with the poor guy !

The manual for your friends machine is here:

http://filebase.heidenhain.de/doku/oma_controls/CD1/tnc/131_135/gb/21427522.pdf.

I'm guessing that "program memory defective" means exactly that. So it may be that the SRAM (memory that requires the battery backup) is bad. To fix this I would:
1) call Heidenhain to get the exact meaning for this error. (if it is RAM related continue below)
2) reseat every socketed chip I could find.
3) If that doesn't fix the problem you would need to be able to identify the RAM's and replace them (may require desoldering/soldering)

If you need help identfying the RAM or finding a replacement part let me know.

Thanks to ya all.

I've translated your suggestions and transmitted to my friend. We'll see...

Speaking of electric / electronic problems, I've been told recently that using a DRO counter without all the axis beeing plugged could lead to failures : true or not ?
I'm a bit concerned about it, since I currently use a three axis Heidenhain DRO n a machine that only has two scales (I can't seem to get around and finally INSTALL that z axis... )

[ 09-29-2006, 09:18 AM: Message edited by: T. NGUYEN BINH ]

T:
What model DRO? Think that is an industrial myth. I have a Heidenhain Positip 750 and it has 4 imputs for scales but i have only 3 and can't see any trouble with it in 3 years of operation. You have to be careful not to touch the pins for the scale i am told as it could cause trouble with the electronics in the reader head electronics with static ....Think on a Heidenhain box you might be able to enter the peramiters and turn off that axis if you wish. But the easiest solution might be to just plug in the scale. It does not have to be installed to be plugged in and that would elimninate any possibility of trouble. Just place the scale behind the machine until you get it installed.
Cheers Ross

The DRO is an ND750, and the guy who told me that talked about the counter inputs needing to be sorta "loaded"...

I've been using the ND for about 2 yrs without the slightest problem (well, on an ahem... irregular basis, I admit), but I thought I'd ask anyway...