Retrofitting a 1986 Maho MH400E

Hello,

After power on the TNC has to display "Stromunterbrechung".
we have to test a few things:

on your user control cabinet there is an cover on the down side, after you opened this, you have an view at the back of the
TNC.



-check the Input Voltage to the TNC, and if it is fitting to the switch position, (!never turn the switch, with machine powered up !)


if this is ok, first disconnect all the black connectors to prevent from an extern failure, power up again and look if something in the displays has changed. if yes go to the point "Checking Machine connections", if not:

disconnect the centronics connector to the Monitor, disconnect the three round axis scale connectors.


power up again. Something changed?

If not you have to deattach the haidenhain from the machine and open it.
check for loosen connetors, check if the eprom chips are fitting right in there sockets (maybe transport failure). Inside the TNC there is on Circuit Board for Power Supply, its an old school discrete circuit with transformer to get +- 15Volts and 2x 5Volts. An electronic guy who is not born in the tablet and smartphone area can check and repair this. if the PSU is ok, there will be some other error inside the TNC, i have a few schematics from the boards, but not all. But this can become much time effort, even some of the ICs are not available anymore.

If somethings changed, and you get the Display "Stromunterbrechung". Step by step reconnect the axis scale connectors and the monitor connector to find the one which causes the failure. Then we can go further.


Checking machine connections

first check on every connector which has pins for 24V and 0V if there are present and not open circuit.


After this, Step by Step reconnect the connectors, to find the one which causes the fault, then we can check the wire from the connector.


My guess is, that the intern power supply from the TNC has gone faulty, maybe due to wrong inpult Voltages. What are the Mains Voltages in your country?

regards

3 phase 400 V ?/ 50 Hz in New Zealand. The Maho 700 c was working then stopped. A circuit board from the TNC 135 was sent to Germany and I understand the Eproms were replaced. The Maho ran again for a while and then stopped. It has been out of action for a few months. From what I have read, the age of the screen could be another future problem.
Thanks db1981.

If you ever have issues with your display, buy an "xvga box" on ebay and plug a normal monitor of any kind into it. The adapter box will convert almost any kind of ancient industrial video signal into "standard" vga (of course it's no longer the standard, but there's a port for a VGA cable on the vast majority of desktop monitors). You can then dump the original display. Since I went through that, I would strongly advise against buying a replacement that's sold as a replacement, they are ridiculously overpriced compared to the adapter box. Also, whatever newer display you end up using (e.g. from an older PC, or just a cheap unit from a sale somewhere) can then be left for the retrofit. That's what I did on my machine - I had the same screen for the Philips 432 control and LinuxCNC.

The risk with an ancient CRT monitor is that it has a trafo unit that amplifies voltage for the purposes of shooting the ray. It operates at very high voltage (mine was 30 thousand) and can fault by just burning up. It might be impossible to find a replacement part and it's usually too late to fix once the problem occurs.

This control is so old, it is probably only CGA video. The cool thing is that old classic space invaders machines are also CGA, so there is a market for replacing their monitors when they die.

That XVGA Box is nice, but the cheaper solution (exspecially as you may still ditch the TNC even once it works again) is a "CGA convertor" from Ebay for about $25.

The first part of a LinuxCNC conversion does not start on the machine. You'd start by getting a PC (I used an old ITX PC which has very good latency), and downloading/ burning a live image of LinuxCNC. Get that installed and running on the PC.

You would also need a set of MESA cards. I used 5i25/7i77 for the main motion control and encoder feedback. Given that you have little space in the control cabinet, and the TNC was in the user control module, you might be better off with the Ethernet MESA cards, as you could separate between the PC in the user control module and the 7i76E in the electrical cabinet more easily .

I have no idea of the Siemens PLC interface? Does it communicate with the TNC through a serial bus? Maybe there is a MESA card which can interface with it in that protocol. Worst case, you'd ditch the Siemens, add a Mesa7i84, and control the 24VDC relays directly.

You can also get the Mesa hardware installed and confidured, before you lay a finger on the MAHO.

The S5 does gearswitch, Hydraulic pressure, Lube, Spindle relais and managing of
the parallel manual / TNC control.
Interface are only a few binary in/out and an 4 Bit Gray/BCD code for the gearstage.
All the S5 internals will completly moved to linuxcnc.

I did use ethercat as hardware interface and placed a few I/Os at the position from the S5.
The I/Os from the control Panel, Analog Outs, Encoder Cards and the EXEs for the linear scales are placed in the second cabinet. The second cabinet has been for 4th axis, Spindle Inverter and other extras. Thats the location where Chris has storaged his books at the moment. (his google photos link)
An mini pc i have placed in the control panel.

Question --- Is the 24 V d.c. supply that was measured to be 29 Volt on the C700 MAHO, some what too high in voltage? 24 times 10% =2.4 volt which would be 26.4 volt D.C. or at plus 15% would be 27.6 Volt D.C.
Guess my real question is what is the measured D.C. voltage you guys are seeing on your machines?

For a Phillips display replacement ---- Look for a Neovo F415 ( 15 inch ) LCD . Might try the Aust E-Bay . the F415 works on the lower sweep rate . Don't remember how low of a sweep rate it will work at but Neovo had it noted on their web site. I picked up one for $32.in the U.S.A. Do understand the F415 model hasn't been made for some time . A Neovo --Xvga box ---CGA converter will all work but to me it is a question of what is readily available at a rational price. Kind of like Manuka Honey prices/stocking in New Zealand or from New Zealand but in New York city..

Chris

---

If you don't have a manual for the Indramat servo drive you might ask Mark if he help you get one. To me the documentation is extremely useful even if you keep the machine as is or convert to Linux CNC.

the 29Volt is a bit to high, but not the cause of the problem.
The Machine was built for 380/220V.

I believe Brad measured them without e-stop switched on, so this is the Voltage without any load.

I remind that the big transformer in the back has other windings for higher main voltages, so they can switch them.

Did you press CE button after stromunterbrechung?
sorry, type too quick, read too slow (:
If you need some parts for tnc I could probably find some... I am from middle EU.

Hi All,

I have already had the TNC to my electronics serviceman, He has replaced capacitors and found the 5V Rail was down to 4.75V, he has fitted an external 5V supply to the internal 5V Rail.
The TNC would not complete the startup sequence while it was being bench tested without the Maho Connected to it.

Brad

Hi Brad,

this sounds like bad eproms to me, but chris wrote that the eproms are already exchanged....

Did you have an look on the service manual from the tnc.
In this you will find test routines for the single boards, and description of the leds.