Electronic gear box for Pfauter 320

Hello
I am (was) repairing a Pfauter 320, coq wheel milling machine. It is from 1979, and the question is whether to continue.
The Electronic gear box between the spindle and the table is probably broken, at least I have 2 analog PCBs (no 47) which acts in 2 ways: The original board drops to -15V for motor speed (on a 10V signal), and when running is jumps from +15 to -15 causing the old servo drive to burn. My guess is that it caused the problem in the first case. The replacement board gives 0 speed when working. This causes the gear box to give a "synchronise not ok" error, what a surprise. When start the motor (servo) by a small signal, the gearbox reacts and we can see that it tries to adjust. By a small switch from our signal to its own cause the motor to stop - zero speed. We tought that it might not start by some reason.
All this gives a number of questions, so we migth replace the gear box. It only gets some signals from 3 inc encoders (spindle, table and the Y axis for tilted wheels), gives -10 to +10V out - but has a large number of thumb wheels for control. Replacing will be "fun" because of the 188 wires from thumb wheels.
We dont know all what is going on in there.... so.... replacing it can be a long run.
There are a number of questions: 1) does it work with the new Mentor 2 servo drive? Is the new servo the problem? [replaced Heldt&Rossi] 2) encoders give signals, and seem ok, but....? 3) 11 PCBs from 1979, lots of logic and analog stuff mixed, lots of things I do not understand. It is full of surprises 4) old (E)proms, for decoding such as 5610 and 82s23/123 (they are the same)
Next, we have no idea what else there might be of problem, not to mention the future.
Can I replace the gear box? Or repair it? Or should I just hang myself for getting involved in this project?
WBR Sonnich
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jodleren wrote:

I don't know the machine or what the controller is intended to do. Are there documents for the machine? There's a lot that's hidden. The type numbers or the EPROMs is not as important as what is in them.
If there is a spec of what the gearbox is supposed to accomplish and the inputs it receives from encoders, it might be easiest to replace it with more modern hardware.
Jerry
--
Engineering is the art of making what you want from things you can get.

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On Mon, 16 Nov 2009 08:20:26 -0800, jodleren wrote:

This is the kind of question that may have a far better answer from someone who has experience with the equipment. There's at least one CNC newsgroup out there -- I have no idea how good it is but I do know there's a lot of politics and a little bit of useful information that leaks from alt.machines.cnc into rec.crafts.metalworking.
Try there (maybe the metalworking group, too), you'll have a better chance at getting the attention of someone who's been there and done that.
All you have to do is wade through a bunch of extremist postings from all areas of the political playing field, including some you never thought existed.
--
www.wescottdesign.com

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You'd be wise to consider the risks in doing this sort of thing. I've attempted it myself in the past, and you can easily find yourself at a genuine dead end. All you need is an additional failure to occur, either random, due to the fact that things are being disturbed, or by someone slipping or dropping a tool inadvertently. Basically, the only chance of success is if nothing else significant goes wrong, and for equipment that old that's far from certain.
Also, if you do succeed, how long before you get another failure? For this level of equipment, you almost always need some sort of external support in the form of spares, or information.
I would think hard before doing it as a business decision unless the payback from success was extreme, and alternatives close to prohibitive.
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Hello
I read all of the answers, and it only confirm my question(s). Lots of unknown stuff, not to mention the risks of replacing it and when the next problem(s) will occur... I think I will let this one go, becuase it sesms to be just too risky.
Replacing something unknown might also be a dead end. And then something else will break down.
WBR Sonnich
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