Repair.IT – Eagnas stringing machine tension head with LED display

Just over a week ago, I was asked to look at a couple of Eagnas electric stringing machine tension heads.  These are similar to the Hawk 126e with LED display.  One tension head was pulling much too high in tension, the other just broke my string because it didn’t stop pulling, and almost pulled my electronic calibrator apart – I remember seeing the display go up to 95 before the string snapped.  I was only testing it at 20lbs.  Note to myself, next time – use badminton string so it should snap a lot earlier without going to such high tensions.

Ok, this machine that didn’t stop pulling – I took it apart – it wasn’t easy.  I eventually worked out that it is best to remove the 240/120V selection switch first – there are two screws under the label.  Then coax the front switch out through the front panel, and remove the six plugged in wires – after noting down which wire goes where.  Also remove the push button switch out the front but leave it loose.  After removing the four bolts that hold the cover in place, it was now possible to lift the cover and essentially manouver it off. Then reconnect the front switch to the correct wires.

After doing all of this, I then found out why the machine would not stop.  When the motor runs and pulls hard enough, a long lever should push onto a microswitch that will then stop the motor.  The part that was supposed to press onto the switch lever didn’t because the lever had bent away from it.  I bent the switch lever back so that it would activate.  Then I wanted to stop it happening again – so I made a little piece of wood, that would fit under the switch mounting that would stop the switch lever from moving sideways.  It will still move sideways, but not enough that it won’t be pressed when the right tension is reached.

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Next step was to check the tension that it pulls at.  To adjust the tension, I need to adjust these small trimmer potentiometers, the ones in blue.

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I mounted the tension head onto my test bench and proceeded to adjust and set the tension at 55lbs.  This machine would be used for tennis.  If it was for badminton, I would adjust it for 25lbs.  Once this was done, I put it all back together and then did a final calibration check.  This is by setting the tension at 20lbs then pulling and recording the tension that was reached, then increasing by 5lbs, etc until I get to 65lbs.  I can’t go any higher with my test bench because the tension calibrator support was starting to bend.  I will add another piece of steel to stiffen it for future testing.  Finally a photo of my test bench with it tensioning at 50lbs and a slight cluttered working area – lots of xbox controllers.

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[Note]  By measuring the tension at various points, we can plot this onto a chart so that we can determine what setting we need to get a particular tension.  This is what calibration usually refers to.

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5 thoughts on “Repair.IT – Eagnas stringing machine tension head with LED display

  1. wes says:

    Please help with fixing an Eagnas Hawk Tension head. Problem : Have to adjust tension and recalibrate after turning machine off and on.

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    • Wes, if it is a similar model, it should not be necessary to recalibrate if the machine is turned off and on. Sometimes the potentiometers that are accessible at the front may not be making contact properly so that might be the reason. To fix the contacts, it is necessary to move the contacts clockwise and anticlockwise a few times, but try to position it back to where it was. I.e. using a Philips screwdriver, turn one way – a quarter turn each time, until it gets to the end, then turn it back the same number of quarter turns. Then from that point, continue the other direction, then come back. Do this on both adjustments a few times, and it should be ok after that. If you have a digital tension meter, I usually use that to check the calibration. These machines will not be linear, i.e. if you adjust it to be correct at 55 lbs, then it will be much lower at 30 lbs, and could be higher at 65 lbs. It is just the way it is.

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  2. ian says:

    I have a tension head (eagnas?) which uses the same components and want to replace the potentiometers . One is not working but both have damaged adjusters due to rough treatment. Are they readily available and what would be their rating etc.
    Thanks Ian

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