Blew up my original 5C

[BennettPrescott]

I've got an original 5C indexer (with the 150 oz/in. motor) that I appear to have blown up. I was replacing the sealtite to the motor and got a pinout wrong, and ever since then the unit fails to do anything but blow 3a mains fuses. The motor checks out OK (and if it were the problem one would imagine I'd be blowing the 10a motor fuse) so it must be the drive unit. When I turn it on now it's OK, but whenever it closes the motor actuation relay there's a very loud hum (from load on the transformer, I assume) and then within a few seconds the mains fuse pops.

Does anyone have any experience repairing these units? I'd rather spend some time bungling around on my own than spend $750 at a repair shop or $5,000 for a new unit. It would be OK if it took a week to fix this, we just finished the last major batch of work it needed to do.

[gar]

051110-1215 EST USA

BennettPrescott:

If the indexer uses a DC brush type motor, then if you apply a small DC voltage, may be 12 v, the motor should probably rotate. The 12 v source should be current limited, may be 2 to 3 amps. A voltmeter and ammeter monitoring this would be useful.

Unless you are absolutely sure of the wire pair that feeds the armature do not run the experiment.

If the motor is a so called "DC brushless", then it is not easy for you to test it.

If DC brush type and it rotates, then you could experiment with various voltages.

If this indexer contains a brake, then the brake would have to be released to rotate.

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[BennettPrescott]

It's a stepper motor on the unit... an older two-phase Slo-Syn model from Superior Electric (now Danaher Motion). The motor tests out fine and I can get it to step, I had a Danaher tech walk me through testing it. I'm further convinced it's not the motor because the control unit is blowing its mains fuse, not its motor fuse.

Haas no longer has any sort of support (not even drawings) available for this 5C control unit, so I can't even test out parts and replace faulty ones (assuming I haven't lost an IC). Basic continuity testing reveals a few places where there could be a problem... there's more than one diode that tests good in both directions.

Anyone have one of these units? Anyone want to sell me one? Anyone have a spec sheet?

[gar]

051118-0916 EST USA

BennettPrescott:

What do you mean that a diode tests good in both directions.

Note a diode is a non-linear device. Ideally it would have infinite resistance when reversed biased, and zero resistance in the forward direction. Today practical diodes have near infinite resistance in the reverse direction, and moderately low but non-linear resistance in the forward direction.

A sample 1N4148 small signal diode has the following measurements in the forward direction:
010 ma 0.728 v 72.8 ohms
020 ma 0.771 v 38.6 ohms
050 ma 0.834 v 16.7 ohms
100 ma 0.893 v 8.93 ohms
150 ma 0.937 v 6.24 ohms
200 ma 0.974 v 4.87 ohms

Sample measurements on several diodes with a Simpson 270 and a Fluke 87III follow. Note the Rx100 scale on the Simpson was used because this has a 6 v source voltage thru an internal resistance. The fluke has two different positions "diode symbol" and resistance. The source voltage on the Fluke is low for the resistance position, and is more like the simpson on the diode position. All these read OL (out of range) or infinite in the reverse direction. Thus, only forward readings are shown.

1N4148 small signal diode.
0.605 Fluke diode
1.64 M Fluke resistance
700 ohms Simpson

MR752 6 amp diode.
0.488 Fluke diode
1.88 M Fluke resistance
500 ohms Simpson

1N6095 30 amp Schottky, low voltage drop.
0.150 Fluke diode
1.00 k Fluke resistance
100 ohms Simpson

If you use an ohmmeter range on a Simpson or Fluke and the reading is near 0 in both directions, then the diode is bad or you have a very low resistance parallel path.

You have various possibilities to repair or replace your driver. One possibility is to replace the power side of your driver with a Gecko module, or equivalent.

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[BennettPrescott]

Originally Posted by gar What do you mean that a diode tests good in both directions. You have various possibilities to repair or replace your driver. One possibility is to replace the power side of your driver with a Gecko module, or equivalent.

Sorry, I should have been clearer. The diode has continuity in both directions when measured with a cheapo analog meter... most of my work is high voltage (125-250v) electrical, so I don't have anything better than a basic digital Ideal multimeter, and I made these meaurements with an off-the-shelf ratshack meter.

Where is the power side of my driver? Do you have experience with these controls? I'm not much of an EE.

Thanks for taking the time, Gar!

[gar]

051118-1314 EST USA

BennettPrescott:

I do not know what an Ideal meter would read, but it is probably similar to a Fluke.

If you use a 1.5 battery with a 100 ohm 1/4 w or higher wattage resistor in series and connect this to the diode and measure the diode voltage and it is less than 0.05 volts in both directions, then the diode is bad or there is a low resistance path around the diode.

The power driver portion of the control should consist of 4 large transistors, probably mounted on heat sinks. These are the switches that directly drive the motor coils. There are probably diodes associated with these transistors.

Search this forum and the Internet in general for information on stepping motor drivers and study how they work.

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[BennettPrescott]

Those transistors are easy enough to find... I'm not sure that they'd be easy enough to replace, though. How would I find the control logic circuits that drive them?

[gar]

051120-2205 EST USA

BennettPrescott:

You need to find someone in your area familiar with stepping motor drivers, and electronics in general.

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