Repair.IT – Eagnas Plus 8000 Electronic Tension Head

A follow-up to my recent “Review.IT” article is in order. This is the one where the load-cell had a wire pulled off of it. After some inspection of the load cell – that is, after removing the silicone compound that covers much of the strain gauges, I could see that everything else was intact. If I wanted to do the repair, all I had to do is to connect the yellow wire and then put a blob of silicone sealant on it.

Sounds easy, doesn’t it – except that the pads are very small and the wire is very thin. I put it onto a holder that allows the load cell to be held by clips, then positioned a magnifying glass over the load cell. In this way, I could clearly see the pad that I was soldering to, and of course the yellow wire. This was done in due course – then the other three load-cell wires were connected. All joins were then covered in heat- shrink.

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Load cell connected finally!

The other tension head came in as expected – so using this one, I was able to determine the load-cell connections. On inspection, the white goes to green, black to red, yellow to yellow (which was still connected) and red to black. The photo above shows the heat-shrink in place, but not yet shrunk.

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New Eagnas Plus 8000 internals

Here is the load cell and connector mounted back into the tension head with the chain re-attached.

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load cell attached with chain

Here is a close-up of the mounted load cell – I had to replace both of the screws that hold it to the chain and the carriage because the old ones had been stripped – I think because the original screws were not strong enough – hopefully, these ones will last longer.

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The New Eagnas Plus 8000

Now a final photo of the completed unit attached to my test bench ready to have its calibration checked and adjusted if needed.

By the way, notice how the blue gripper assembly doesn’t yet have the gripper installed? The reason for this is that I had to modify the assembly because the fastening screws were bent, by going through a 6.4 degree bend – that is the slope of the assembly relative to the horizontal. The holes drilled and counterbored in the assembly were perpendicular to the assembly, but were not lined up with the vertical holes in the mounting.

I put the gripper assembly into my mill and adjusted it to have a 6.5 degree slope, then used a 10mm end-mill to do the counterbore. This was followed by a 6.5mm drill to ensure that there was a vertical hole going through the assembly at the right angle. After doing this, the mounting screws can now be tightened up properly without having to bend in the middle.

The next tension head to look at is the one that came in, apparently had been smoking – and the transformer looks like it has been cooked, with the varnish having boiled out of it.

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Repair.IT – Eagnas Flex 737e or 767e electronic tension head

This blog does get around, especially for those who are searching for “Eagnas repair”. Back in July, a comment came through from a reader asking if I knew what value potentiometers were in the tension head and whether they were available. I replied saying that the value is written on the trimpot and they were generally available.

Later I emailed the reader as I realized that he is from Australia as I have repaired units like these for other people. Eventually he got back into contact and would drop the tension head to me when he was passing through Sydney sometime in the future. This did happen on the 4th of this month, he had already purchased some trimpots that should be suitable.

The original trimpots had been roughly treated in the past, not by this reader but by a previous owner. It was a relatively easy manner to desolder the trimpots, then install the replacement trimpots after bending the leads appropriately to fit the circuit board. Coincidentally, both trimpots were marked P102 which is a 1K-ohm and these happened to be the ones that he purchased.

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New and old trimpots

As you can see, the original trimpots look a little worse for wear. The newly installed ones look perfect. The next step was to reassemble the unit, mainly put the cover back on, then feed the six wires out the front panel to a double pole two position switch with center off. This was a problem since my previous wiring for the switch had slightly different colours – so off with the cover, then trace the wiring to determine which way the switch should be wired.

Eventually, I worked it out. One pair of wires, the red and the black are the motor wires. Then another pair – blue and yellow are the +24V, so are power. The remaining two wires were brown and red. Fortunately, the reader had put cable ties on each group of three wires, because these are to different poles on the switch. The switch works as a reversing switch, applying power to the motor in one direction – to tension, and then to reverse the motor direction to release the tension.

One group of wires is brown, red and yellow – so the red is the motor goes in the middle then brown on the II position, and yellow in the I position on the switch. The remaining group of blue, black and red – again black is the motor so goes in the middle, then this time blue must be the opposite side to the yellow, so goes in the II position, then red finally in the I position.

The final test is to power on, and check that when I click the switch to the I position, that the gripper turns clockwise. Nothing happened – ok, what is going on. I got the cover off, then looked at the small circuit board behind the motor – I had to remove a couple of connectors from that board, and I noticed one connector wasn’t lined up, i.e. wasn’t plugged in properly. My fault – when I pushed it back in, I though the pins had engaged but they hadn’t. It was a tight fit, so this time, carefully I manoevered the connector until the pins had gone in, then pushed it home. A visual inspection showed both connectors were lined up – great.

Power up again – after connecting the switch, and fantastic – the I position moves the gripper clockwise, and switching to the II position, the gripper moves anti-clockwise then stops when it reaches its home position. Normally this will have released the tension on the string, but if it hasn’t, the red button can be pressed which will turn the gripper anti-clockwise another time.

Once reassembled, it was time to check the calibration. These trimpots are used to adjust the gain in the various amplifiers on the circuit board. I mounted it onto my test bench then started with low tensions and working up to the high tensions – and once I was sure that things were working – I set it to 55 lbs and did a tension test.

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55 lbs on the tension head

It is working, so with a few small adjustments, I did a chart from checking tensions from 20 lbs to 60 lbs. This was then made into a calibration chart that could be used to work out what setting is needed to get a particular required tension. Generally though, this kind of tension head is not very accurate and the tension can vary by a pound or two, even from one string pull to another.

Of course, all of this did not happen on the same day, but it is an idea of the sort of effort that is needed. By the way, this kind of tension head is best calibrated on the stringing machine that it is to be used on. The reason for this is that if the string is not horizontal which is where I have calibrated it for, then the resulting tension can be low or high.

I.e. if the string is sloping downwards towards the tension head – the tension being pulled is slightly low, but if the string slopes upwards towards the tension head – then the actual tension will be higher. The reason for this is that as the gripper turns and pulls the string tighter – the gripper assembly which is pivoted on a L shaped bracket, will lift causing a microswitch to be activated. The microswitch is located near the front left corner – a clever use of gravity actually. Now, if this tension head was used on the moon, what tension would be get if we tried to tension for 55 lbs?

P.S. The small black knob on the right below the LED display, turning this knob moves the wiper of another potentiometer but also compresses or releases a spring. The spring acts against the bracket causing resistance to the pivoting. In this way, turning the knob anti-clockwise will compress the spring, and give a higher display – so the result is a higher tension. The calibration trimpots are used to set the display reading to be close to the actual resulting tension.

So, on the moon with one-sixth of the earth’s gravity, the resulting tension would obviously be lower. The weight of the gripper mechanism and the motor and gearbox would probably be 15 lbs on Earth, so the tension we would get on the moon would probably be 12.5 lbs less – does that sound right?

Rekey.IT – Granny Flat locks keyed alike

I am not a locksmith, but I am an engineer. Often engineers are required to fix things that are not always broken – anyway, I digress.

On Wednesday, a locksmith came to install a Lockwood 3582SC narrow mortice lock into our new aluminium gate. The gatepost is a standard 50x50mm aluminium extrusion, and as it was an outwards opening gate, the choice of locks was very limited. The gate was also part of a new fence that was installed at the front of our brand new granny flat, and this gate was the only exit from the granny flat onto the street.

If we were not concerned about safety, we could have used any of the inexpensive gate locks, where the pin would have to be on the fixed post, and the latch is on the gate. We didn’t like this idea as the thought of a pin sticking out at any height would be an accident waiting to happen – i.e. child running past knocking into the pin, or if it was higher, an adult poking his eye out.

So we went with a much more expensive lock that fits inside the gate itself, with keyed cylinders inside and outside, and a blocker plate to stop people from trying to jimmy the lock – not that it could happen, but why allow people to think that it could be done.

Yesterday, we had been thinking about the locks on the granny flat. We have a key for the gate, then a key for the security screen door, then a key for the front sliding door then another key for the back door. This makes it four keys excluding the window keys. How convenient would it be just to have one key. Also thinking about what would happen in an emergency – you want to exit quickly, and fumbling about to find the right key can be problematic especially when panic starts to set in.

We decided to make changes, so that no key was necessary to exit the granny flat. At the same time, we should get the locks rekeyed so that only one key is needed to get in and to lock up when leaving. The back door deadbolt was replaced to be a single cylinder instead of the current double cylinder.

Did you know that getting a lock cylinder rekeyed costs around $38.50 each, so a lock with two cylinders would cost double that. In actual fact, most locksmiths will sell you a lock, and key it to your existing key free of charge, so instead of rekeying, you could buy a new lock for your key – especially since I wanted to change things around.

Anyway, I was going to do the rekeying – the locksmiths would do that, however for the gate, I was just going to replace the inside cylinder with a turnsnib – a knob that takes the place of the key turning. Ok, it isn’t as secure as a key, but in an emergency, getting out quickly is safer than being secure.

I ordered the appropriate locks and cylinders for what I wanted to change and got the turnsnib to put onto the gate lock. It is a simple matter of having the gate open, then removing two screws to get the cover plate off, pull out the retaining pin for the inside cylinder, remove it and insert the turnsnib, then put the retaining pin back on and install the cover plate again.

Sounds simple when you write it like that. In practice it wasn’t. I could remove the cover plate screws but couldn’t get the cover plate off until I loosened the two screws holding the lock in place. Then the retaining pin would come out until I loosened the handle furniture. Ok, got the pin out eventually, then removed the cylinder and put in the turnsnib cylinder – almost done.

Then I couldn’t get the retaining pin inserted – I could get it partly but I didn’t want to force it. Better get some advice, since I had to take the new deadbolt back anyway, because my key wouldn’t turn it. I put everything back on, but then couldn’t get the handle furniture back on.

The advice from the locksmith was that I may need to hammer the retaining pin into place, since it can be tight – ok. After much playing around with the lock, I eventually had to remove everything from the gate. Remove the blocker plate, remove both handles, remove both cylinders, then remove the lock from the gate. Did I mention that the locksmith spent an hour and a half installing this in the first place, and charged me $200+ to do it and here I had the whole thing taken out!

With the lock out, I put both cylinders in, the keyed cylinder was easy, but the retaining pin for the turnsnib would go in with difficulty except it would jam when it had to go in another 3-4mm – this is the part where the hammer is needed. I put the lock back in, then tried putting the cylinders in – this is where I found that the cutouts for the cylinders were the problem – the cutouts were out of alignment so the turnsnib cylinder would jam up against the side of the gate.

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Out comes the lock, then in with a metal file and filed it until I could have the cylinders in without jamming. Next to check why the handles would not go in properly – again, the holes where the screws go to secure the handles were out of alignment, this time by a few mm. Out with the lock again, then in with a round file to open up the holes. I had to do this to both sides, until finally, the lock and handles could go in without difficulty – fantastic.

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The photo shows the lock in place without the cover plate, and both handles installed. Install the keyed cylinder on the right of the lock – done. Install the turnsnib to the left of the lock, with a few taps of the hammer, the retaining pin went in with difficulty. Then put the cover plate on – it wouldn’t go on flush, but a bit of a tap with the hammer, then tighten the screw – do it again, tighten a little more. The cover plate now is ok to use, so job finally done.

That is, after two hours of effort – knowing what I know now, I might even have been able to install the lock from scratch in that time – if I had an angle grinder to cut the slot for the lock, and the right size hole saws. Actually, I still had to install the blocker plate, but that was easy – only two long screws.

P.S. If I had been able to get the gate post before the gate was assembled, I could have put it on my milling machine and cut all the slots and holes properly for the lock before the gate was assembled – maybe on the next gate.

Regarding the deadbolt, after they fixed up the keying, I installed that easily. The euro cylinder for the security screen door – I had to go to Bunnings to get a M5 countersunk screw, since the original euro cylinder had a 3/16″ screw which doesn’t fit the new cylinder. Did you know that Bunnings only has stainless steel M5 countersunk screws, but plenty of imperial sizes in plain zinc coated.

Oh, the sliding front door lock – is still coming in, maybe in a week – supposedly a standard fitting, easy to do – we’ll see.

Repair.IT – Apple MacBook Pro A1278

Early last month, 3rd November, actually – an old friend of mine who used to have a computer shop up in Gosford contacted me about an Apple MacBook. At the time I recall that it was about someone spilling something onto the keyboard and asked if I would have a look at it. I said that he should bring the power adapter with it when he comes.

Nothing more happened about this until two days ago – 3rd December, when he called again and said that he has gotten his hands on the MacBook and would bring it to me in the afternoon.

When it came in, I could see that it was a MacBook Pro model A1278. I placed it on charge and would happy to see that it was charging, so left it to fully charge. When finally charging was completed, I opened the screen and it resumed from sleep and was faced with a logon requiring a password. The keyboard seemed to be working, so I tried the trackpad – the mouse cursor jumped all over the screen – this must be the problem.

I did a quick search on Google and found numerous posts about trackpad problems with this model of MacBook Pro and also found suppliers for replacement trackpads. Most people were replacing the trackpad to fix the problem. I opened the bottom of the case – which required removing ten screws, three of them being longer than the others. I usually place the screws in an order representing the physical location of the holes where they came out of.

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Put screws in some sort of order

I used my smallest Phillips-head screwdriver to remove these screws. Once the bottom cover was off, I could see that it was a bit dusty inside.

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Dusty insides of MacBook Pro

I also saw what appeared to be a grain of rice next to where the trackpad cable connector was located.

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Rice, anyone?

I removed the grain of rice, then unplugged the trackpad connector and plugged it back in. Then put the cover back on and turned on the MacBook.

The trackpad problem was still there, so I decided to clean the trackpad. I use a soft cloth that I wet first, then wrung dry – so that it is damp. I wiped the trackpad with left and right motions until I covered all of it, then wiped along the edges. After doing this, I turned on again, and the trackpad was responding again – ok, not perfect, left and right motions seemed to be sort of working, but up and down was not. Tried drawing a circle – the result was nothing like it.

I decided to clean the trackpad again, this time with up and down motions, then finally with circle motions along the entire trackpad surface – I used a slightly damper cloth this time. This time, I could now move the mouse cursor all over the screen and make little and bigger circles – I made a little video of it, just to give you an idea.

After this, I opened the case again, and gave the insides a good going over with the vacuum cleaner, then closing up again – turned it on for a final check. To my surprise, the trackpad problem was back again! The trackpad itself can’t be dirty now, so it must be the connector. Using a vacuum cleaner can cause connectors to shift slightly especially those that are pressed down.

I opened up the case again, then removed the trackpad connector – used a fine bristle brush and brushed both the connector and the mating piece, connected back on again – then closed up the case. After turning on, the trackpad was working, and I was able to move the mouse cursor in circles again.

Over the next day or two, I will continue to turn it on and check that the trackpad is working. If it fails again, then it is likely that the trackpad will need replacement – cost would be something like $40 from a number of ebay sellers, as it could be a bad contact on the trackpad connector. I did examine the connector and mating piece through a 10x jewellers loupe and all the contacts looked intact.

Rewind.IT, Reread.IT – Ozito LTR-301 500W Line Trimmer spool

Back in April this year, when my trusty Black & Decker line trimmer was finally retired due to a variety of failures, I bought an Ozito LTR-301 500W Line Trimmer. The Ozito was used successfully on numerous occasions until today, when the line ran out – of course, it does when you have only just started.

If you are like me, you will save a bit of money by using bulk line. As it happens, I had some 1.4mm line left over from an older cordless line trimmer whose battery had failed, and this line had been used successfully on the Black & Decker and now looks like it will be used for the Ozito.

I removed the spool cover and took the spool out – and also consulted the instruction manual for my line trimmer, a step that many people often leave out (for better or for worse).

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Looking at the red arrow, it would appear that the line is wound in the anti-clockwise direction – which I found a little strange, for a number of reasons. Usually, upon inserting the line, we bend it backwards – like a U-turn, then proceed winding, however this is contrary to the instructions (as I read it at the time).  There is an arrow on the spool, which implies that the line should be wound clockwise.

In addition, the instructions said to use 1m of line – when the specifications say that the line is 1.5mm x 4.5m – so I thought I would cut 2m of line first and try it out.  The first time I wound the line, it came out of the hole when I was winding, so the next time I managed to wind it, then did the same for the other half of the spool.

I installed the spool into the holder and put the cover back on.  The power cord was plugged in and on switching on, the line started unravelling.  Ok, I took the spool out again, and then rewound the spool in the opposite direction, clockwise as indicated by the arrow – success, now the line trimmer was working and I proceeded to cut the grass edges.

Anyway, looking back at the instructions, I now read – “wind … in the direction of the arrows on the spool cover.”  Now I realize my original mistake – my mind saw the words “direction of the arrows” and my eyes were drawn to the red arrow that is in the picture, not realizing that this might just be a generic illustration that is used for many line trimmers.  In addition, the spool doesn’t quite look like this – something I did notice at the time that should have rung a bell.

If I had, like most people – just started winding the line on, without resorting to the instructions, I would have gotten it right the first time.  Or like some people just buy the replacement spool and line – part number AACLT-005 from Bunnings for $9.90 – which incidentally has 10m of 1.6mm line.

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Anyway, I think that when the line runs out, I will wind two lengths of 4.5m line.

P.S. When I started the line trimmer with the line wound in the wrong direction, it started unravelling and kicked up a lot of dust and grit which sprayed up straight into my face.  Fortunately, whenever I am using power tools, I am in the habit of wearing safety glasses that protected my eyes, many times – do you wear them?