Installing the Acorn with Adtech CNC drives

[dmbgo]

You never know Marty, I'm always the optimist.

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I have now reached the conclusion, that there is a time for optimism, and a time for practicality.
I think I will replace my damaged servo motor and Controller. Whether or not I also replace the working servo with the same type of servo that I intend to purchase is the current question.
I replaced the damaged resistor on the current Z servo controller's main board and checked the opto couplers, which seemed Ok, at least on the input side. There was no change in the servo's inability to reverse however, leading me to make the decision stated above.
What type of servo/s should I buy? I think I have had enough of chinese servos, so something with an English manual and perhaps some support if required?

[dmbgo]

I'm wondering now if it's possible to use the motors I have with a different ac servo controller? Apart from the Adtech motors from the lathe, I also have a larger Adtech servo, and a GSK servo motor floating around.

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I think I'll start a new thread ab out servo controller recommendations. Thanks to everyone who has helped so far.


Dave

[tblough]

To minimize headaches, i recomnend sticking with drives and motors from the same manufacturer. Fanuc, Mitsubishi, Siemens, ABB, Yaskawa, Parker are all premium brands. Stick with American/German/Japanese and you shouldn't have any problems.

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Thanks Tom

[Muzzer]

It seems fairly likely that the burnt 220 ohm resistor was associated with the loss of function. It seems unusual that you found it had failed short - but given the minimal parts count on the input side of the opto, it's highly likely that the opto LED was in fact damaged. I suspect you are very close to a repair.

If you don't fancy waiting for a replacement, you may find there are other optos on the board that aren't used in your application. I (ahem) recently did something similar to the Yaskawa servo drive I bought for my 4th axis but was able to simply replace the resistor and mend the track to restore function. However, I saw there were several other optos on optional inputs and outputs that I didn't require in my system. I could have removed one of those and used it to replace a damaged one. My mistake was to misread the manual so that I connected up a 24V signal where it was expecting a 5V signal. For 24V operation, a series resistor is required.

[dmbgo]

It seems fairly likely that the burnt 220 ohm resistor was associated with the loss of function. It seems unusual that you found it had failed short - but given the minimal parts count on the input side of the opto, it's highly likely that the opto LED was in fact damaged. I suspect you are very close to a repair.

If you don't fancy waiting for a replacement, you may find there are other optos on the board that aren't used in your application. I (ahem) recently did something similar to the Yaskawa servo drive I bought for my 4th axis but was able to simply replace the resistor and mend the track to restore function. However, I saw there were several other optos on optional inputs and outputs that I didn't require in my system. I could have removed one of those and used it to replace a damaged one. My mistake was to misread the manual so that I connected up a 24V signal where it was expecting a 5V signal. For 24V operation, a series resistor is required.

The lack of a series resistor may well be the root cause of my issue as well.
To go into a bit more detail about my issue, I found the 220 ohm resistor (the burnt one) measured as a short circuit. I unsoldered it, then measured it on the bench - it was 220 ohms. I then put it back. I can only assume that the excess heat that the resistor was trying to dissapate had melted the solder underneath the resistor and caused the short.
I followed the circuit with the meter and found the opto that it led into. On the input side at least this opto measures the same as the other optos on the board - 1.9v one way around and 0.5v the other way around.
This led me to think that the optos were probably Ok, without desoldering any for a proper test.
Do you think I should proceed? You are right, in that I'm probably not too far from the cause of the issue, but I began to wonder whether the time Vs the outcome equation might be starting to look bad.

[Muzzer]

Sounds as if you have a replacement servo+motor on the way, so perhaps you could keep it as a spare for the other axis. Certainly, it seems to measure as an LED and reverse diode pair but it doesn't appear to work as one any more. Given the in-built isolation, the damage couldn't have propagated any further into the unit, so there aren't many compts that could be damaged.

From my own experience, I know that LEDs can significantly lose light output before they finally fail due to overtemperature (which is ultimately what kills LEDs). However, just what this failure event looked like inside your opto isn't clear. I'm guessing that it saw a sustained overcurrent rather than a massive overwhelming splat.

Depends on your appetite - you could give it one last shot if you have the stamina, or simply label the likely fault and put it on the shelf for a future time when you may require a spare.

[dmbgo]

Thanks for your insighful explanation of possible optocoupler faults Muzzer. Its likely that I'll never use the controller again, but does seem too good to throw away. My wife thinks I am a hoarder, keeping old pentium computer boards etc, in case something on them is handy (the parts usually aren't handy, but occasionally when they are, I chortle to the world about my foresight in keeping things).