Reassemble.IT, Repair.IT – Eagnas Plus 8000 Electronic Tension Head

Last Saturday, I got a message that there was a Eagnas Plus 8000 Electronic Tension Head for me to look at. It was apparently new, but not working. I picked it up on Monday, after it had been returned by the customer.

This is a newer model of the Eagnas Plus 8000 that I had worked on previously – a white case instead of the older grey case. This one had been sold to a customer who said it wasn’t working, so the supplier sent a spare circuit board to the customer. Due to some problem with the assembly, it came back to the supplier – which is where I got involved.

The gripper assembly had been removed already – when I examined it, I noted that the microswitch wasn’t clicking when the white plastic actuating lever was pressed. I knew from previous experience that this would cause an error in the self test procedure that would stop the tension head from working.

I proceeded to remove the case and found that the internal circuit board had been removed from its supports, and cables had been removed from the board. Also I found that the drive chain for the carriage was disconnected. This tension head differs from the older one by using a different load cell, a much smaller one, which is connected in line with the drive chain. The older model used a much larger load cell (and probably more sensitive) which was indirectly coupled to the carriage.

Anyway, I had to reassemble everything before I could test it and work out what problem it had other than the suspect microswitch. This reassembly took some time, to remount the circuit board, and while attaching the cables, I found a couple of the contacts on one cable were a little loose – which was causing heating at the contact point. I removed the contacts and adjusted them so that there was better contact between the pins.

Next was to reconnect the chain. The bolt that had been used was a M4 bolt which was bent, and the end was stripped – looks like the nut had pulled loose. If that was the case, perhaps it had not been tightened properly in the factory. I replaced the bolt with a M4 bolt from my nuts and bolts collection, cut to the appropriate length and tightened up. The chain was then reattached which took some effort because it has a spring inside the joiner, but eventually it was done.

I then examined the microswitch which is mounted at an angle so that the plastic lever pushes the switch lever down, however – the switch lever was not bent to the correct angle, so when assembled, the switch was always activated. I bent the lever to an angle such that when assembled, the switch was not pressed. Then pushing down on the white plastic lever, I now heard the familiar click of a working microswitch.

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Switch assembly

Here you can see the white plastic lever – and next to it, the silver microswitch lever. Pressing the white lever pushes down on the silver lever.

I then connected the switch cable and plugged in the power cable, and was glad to see that the self test shows three ticks.

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Eagnas display panel

From experience, if the switch was pressed or not connected at power on, there will be a cross next to 3. Load-cell cable instead of a tick – which can be a red herring, since you need to know that the load-cell cable doesn’t just connect to the load cell, but also to the gripper microswitch. Most people don’t know this, and hence suspect that the circuit board might be the problem.

Once everything was back together, I set the tension to about 20 lbs, then put some string into the gripper with a digital luggage scale to pull and see if it stops pulling, which it did, but it wasn’t at 20 lbs, more like 14 lbs – which is probably ok. Why is this? Because the tension head is usually calibrated at the factory to suit tennis tensions at 50 or 55 lbs. If this tension head is going to used for badminton, then we would adjust the calibration to be more accurate at around 25 lbs. If the user has a digital luggage scale, they can also test it at various settings and end up with a calibration chart which shows what setting gives a particular tension.

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Eagnas Plus 8000 Electronic Tension Head

Here is a final photo of the assembled tension head before I put it back into its box – looks quite nice, doesn’t it.

[Note] Other work done on this was to fix up the slide covers, that had been wrinkled a bit and to realign the slide cover guides to be parallel to the carriage movement. Not doing this causes the slide covers to jam.

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Reassemble.IT – Meade 6x30mm Finder Scope – again!

After I posted the earlier article about this finder scope, I had a thought that perhaps I should check the focal point to make sure that the crosshair reticle is in the right place. The finder scope works as it is, so the lens arrangement is correct. It turns out that I was wrong yesterday – the order from left to right is as follows:  The end piece, then the crosshair reticle followed by the big spacer, then the lens arrangement as per yesterday.

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When I assembled it this way, I could look through the eyepiece and see where the original crosshairs had been broken and curled up against the sides of the reticle.  Sure enough under a 10x jeweller’s loupe, I could just see the broken hairs.  Anyway, it doesn’t make any difference to the focusing of the finder scope as the lens arrangement dictates this, but it now means that when I do find something thin enough, I can fix the crosshair reticle.  So, now again, I have “reassembled.IT” properly this time.

Reassemble.IT – Meade 6×30 Finder Scope

Six months ago, I bought a second hand Meade LXD55 SN-6 telescope. The LXD55 is a computerized mount that is capable of slewing to any object in its database. The SN-6 is a 6-inch Schmidt-Newtonian telescope. I noticed at the time that the Meade 6x30mm finder scope was mounted backwards. The finder scope is a small telescope so usually the big end points to the sky and we look through the little end, however they were looking through the big end – strange.

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Yesterday, I was reminded about this finder scope, so decided to have a closer look. I looked through the finder scope and realized why they used it this way. When viewing through the eyepiece, everything was blurry – a case of not being in focus. To focus the finder scope we have to move the eyepiece section and front lens apart, i.e. move the eyepiece in and out of the tube. Or move the main lens in and out, but no matter what I did, it would not focus. After taking the eyepiece out, I worked out that the tube was about half an inch too short. How is this possible?

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A search through google mentions that some Meade finder scopes also had this problem, and the solution was that the supplier would replace it. This telescope was first released in 2002, so now it was way past its warranty. The only solution now is to work out what was wrong with it.

The eyepiece appeared strange, so I decided to take it apart, noting in which order the pieces came out.

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It was strange – the piece on the right end is obviously for the crosshair reticle, which should be in the middle.

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Both eyepiece lenses are half-convex and judging by the thickness, they should be arranged as a standard Kellner eyepiece.  A Kellner would have the two lenses separated by the small spacer with the thicker lens on the right, with the curved surfaces facing inwards.

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This lens arrangement would then be on the right.  In the middle would be another spacer, then the crosshair ring – which didn’t have crosshairs, and the final piece on the left.  Once I “reassembled.IT“, this is what the eyepiece looks like – quite different from the original which must have come apart and then the owner didn’t know how to put it back together.

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Once the finder scope was fully assembled, it was able to be focused on short distance by moving the eyepiece outwards, and to focus on long distance by screwing the eyepiece inwards. Another thing fixed.

P.S. The crosshair reticle, if it had one, would be at the focal point of the lens arrangement, which can be worked out by looking through to see at which point the image is sharp and focused.  I just need to find some very fine wire or hair and glue them to that piece. Alternatively, use a piece of clear plastic of the same diameter and scribe or draw a couple of fine lines on it.

Reassemble.IT – Black & Decker GL570 Line Trimmer

…continued from yesterday…

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I put the actuator into the vise on my milling machine, then milled the worn pin off it.

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Then I used a 2mm drill and drilled the initial hole for the pin to go into. I do this so that if the first hole is not centred, I can still adjust the position when I drill for the final size.

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I drilled the final 2.5mm hole into the actuator. The pin that I made is just over 2.5mm in diameter so it should press in and be reasonably firm.

I inserted the pin into the actuator, then milled to the appropriate height.  Here is a photo of the repaired actuator.

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Now some of you might not have a line trimmer, so I have a photo of it installed into the line trimmer head.

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I have to say that the this was an oustanding success.  I trimmed more than 10m of edge and the line did not break.  It would advance the line from time to time – I inspected the actuator afterwards, and I can see no real wear.  Not bad what a couple of thousand dollars worth of machinery can do!

The nylon material I used is from a kitchen cutting board – I bought one some time ago as a source of cheap nylon.  I put it in the lathe to turn it down to size, 2.5mm and 3.9mm, then the rest was on the milling machine today.

[Edit]  When turning soft materials like nylon and other plastics on a lathe, it is best to turn down the diameter in stages.  I wanted a final 3.9mm diameter so elected to first turn to a 5mm diameter first, then I turned a section to 2.5mm.  This is because plastics are not as rigid as metals, so will move away from the cutting bit, hence turn down to 2.5mm in small sections until the length of that section is correct, before turning the 3.9mm section.