Repair.IT – Wise 2086 Professional Electronic Tension Head

Occasionally, in the electronic repair world – we may be unable to obtain replacement parts. In a situation like this, we then have to resort to replacing the module that has failed, either with modules from the manufacturer or modules that have a similar function.

This is about my Wise 2086 Professional Electronic Tension Head – which is mounted on my Spinfire Flame Stringing Machine. The tension head allows the string to be gripped, then pulled linearly until the required tension is reached – then, if constant pull is enabled, it will continue to keep that tension. A couple of weeks ago, I noticed that one of the segments on the second LED display didn’t light up. For those who know about 7 segment LED displays, it was the B segment. Sometimes like today, on powerup – it will be working.


Wise 2086 Tension Head – display working

But then later on, the B segment will stop.


Wise 2086 Tension Head – display not working properly

A couple of weeks ago, I emailed an enquiry to the supplier in Melbourne, Tennis Warehouse – from where I purchased this stringing machine about three years ago. I asked about any problems if I open up the tension head and mentioned the display problem. I had heard on the internet that occasionally, opening up the tension head would give an error on next powerup, that would require some procedure to be followed. I received a quick response that this will not happen, and that the screws are different lengths – something to watch out for when I open the case. Also that the display board is available for $45.

Just a week ago, on Friday, once I had finished stringing a few racquets – I opened up the case, then had to remove the main carriage to get to the display board. I removed the board and checked the part number of the LED display. It was a HS-3101AS – which is a 0.3 inch display but in a larger housing with 10 pins. I checked my usual supplier – element14, to no avail – this part didn’t appear to be available and I was unable to find an equivalent. A search on the internet also gave me a possible equivalent – HS-3101AX, but this also didn’t help.

I could find other similar size displays but when I check the pin connections, those are in two columns of five pins, 5 mm between columns, but mine are 7.62mm between columns. I could find it on alibaba, except that they only indicate it as being an integrated circuit will no actual photograph – so I was hesitant at ordering something, sight unseen. I decided then, to bite the bullet and order a replacement display board. I had to email a photo of the display board so that they could confirm the correct replacement. Then on Thursday – my replacement board arrived.


Display board for Wise 2086


Display board for Wise 2086

The top on is the original, version 3.1 and the replacement is at the bottom – version 3.3. Some slight differences – the main thing being that the speaker was moved, making it much easier to install the board.


Wise 2086 Tension Head

Here is a photo of the board installed – at the top. Previously the speaker would get in the way of my fingers when trying to remove and install the small brass nut.


Wise 2086 Tension Head

Then a photo with the carriage mounted back on.

Next thing to do is to work on one of the base clamps on the stringing machine – which had been causing problems that it would unlock, when I didn’t want it to. Tennis Warehouse sent me a replacement base clamp at the same time as the display board which was very good of them.

The motto of the story is that you cannot always replace component parts – in fact, not many companies will do this, even for manufacturers – they usually replace the module. Sometimes, if the modules are valuable – they are returned to the factory for refurbishment – which usually means replacing the faulty components, but not always. The common factory refurbished cameras and whitegoods – are usually just repaired with replacement modules – often happens with goods that are dead on arrival, they go back – repaired by swapping modules, then comes back out as factory refurbished at a very good price and with warranty, generally.

Repair.IT – Sedco 24V / 12V Power Supply

Just over a week ago, I was asked if I repair power supplies – I said sure, so this Sedco 24V / 12V Power Supply was carried out to my car and placed in my boot. It certainly looked heavy, and when I got it home and opened the cover – I realized why.


The insides of the Sedco power supply

There are two 12V batteries inside, obviously looking very much the worse for wear – the acid corrosion on the negative terminal of the right side battery contact is a sure sign of battery failure. Certainly when I measured both batteries, I was getting only 6V on the left one, and about 4V on the right.

Ok, the usual checks are the fuses – are they intact? Yes, they measured fine with my multimeter. The actual power supply is in the metal box at the top left – the one with the five multi-wire connectors . The left connector is the incoming mains power, next one is the battery connection, then the output voltage, and two with lots of wires going to leds, etc.

Next thing is to remove the power supply. This was a fairly standard switched mode power supply, however it has a couple of plug-in boards that connect to the main circuit board. The incoming mains is rectified and conditioned by the plug-in board on the left – I don’t actually have a photo of it, but it is where the mains connector is attached. The second plug-in board seems to be for the two multi-wire connectors, doing things like driving the leds on the front panel.

This little board did have three electrolytic capacitors that were bulging – we have mentioned this previously, that these have most likely failed. I didn’t have 1000uF 35V 105C capacitors in my stock, so had to arrange to get them. I got these in due course and replaced them together with a 100uF 35V capacitor that had also failed. I checked also the semiconductors – such as diodes, mosfet’s – but they all appeared to be intact. The fuses being intact also indicates no catastrophic failure.

The power supply was reassembled, and everything connected back together, then power was applied, and… nothing – no lights, no bang – basically nothing happened other than the switch clicking on. Ok, so the power supply is not starting up – what could be the problem?

Removed the power supply and started having a closer look at the main circuit board. A fairly standard layout – the startup circuit is the one to look at. I spied a small electrolytic in the startup circuit – when I measured the ESR, it was 8.4 which is very high. Unfortunately, the capacitor was hidden away with other large components near it so I could not read the value of the capacitor. A low value capacitor could potentially have a high ESR so being high is not necessarily a definite sign of failure. This capacitor is connected to a UC3845 SMPS controller – which is a fixed frequency current-mode PWM controller.

I did a bit of research on this controller and came across a little tit-bit of information, that if the Vcc capacitor was faulty, a UC3842 PWM controller likely cannot start. As this UC3842 is in the same family as the UC3845, I thought that this capacitor was likely to be faulty. I then desoldered the capacitor and found that it had a value of 100uF 35V. At this value, definitely the high ESR means that it had failed. I had one in my stock, so replaced the capacitor – then reassembled everything.

Finally, I connected up my power meter to the power supply then turned on, and… it powered up, at least the power light was lit – also the low battery light was on. I turned off and went to have something to eat. When I came back and powered up again, I could now see that the 24V and 12V lights also came on. I measured the power rails on the back of the power supply, 12.2V for the 12V rail, and around 25.2V for the 24V rail.

The 24V rail was fluctuating a little and certainly wasn’t 24V but higher. Why is this? Ok, it has to charge the batteries, of course, so needs to be higher than 24V – at 25.2V, the batteries could be connected almost indefinitely and should not show signs of overcharging (ideally). Of course, the batteries were not in good condition, so maybe replacing the batteries would give a more stable 24V rail. Anyway, it certainly looks like it is now repaired and working again – I can’t do more until the batteries are replaced.

[Note] This power supply is used in nursing homes and hospitals associated with medical care. The power supply will provide 24V and 12V normally – and if mains power fails, it will still deliver this via the internal batteries until such time as they go flat.

Repair.IT – Laser switch on my Makita LS1017L Sliding Compound Saw – at least for the moment

For my deck building project, I bought myself a Makita LS1017L sliding compound saw.  I did some research first, thinking about the size of the timbers that I would be cutting.  Most of the comments I found were that people bought a compound saw, and later wished that they had bought a sliding one.  A non-sliding one is like a chop saw, start the blade spinning, then pull it down to cut the timber.  A sliding saw allows you to pull the saw forward and down, then start the blade, then cut the timber by pushing the saw away from you.

From the use of the saw, I found that there is a bit of difference on the cut – depending on how you use it – like a chop saw, and a sliding saw.  I could get a very nice finish on the cut by using the sliding method.  This particular Makita saw has a laser line that can be adjusted to sit on either the left edge of the blade – or the right edge – or actually at any point in between.  It was set to the left edge and after a few trials with a scrap piece of timber, I could see where the edge of the cut would be.

I had the saw in the front of my garage – because all the timber had been delivered to my driveway and I put all the timber into the garage – leaving no room for my car.  Basically I would cut up the treated pine, in the right dimensions to suit the deck that I was building – or part thereof.  Then I would put the pieces together, then screw them together in the right order to make up a frame that the decking boards would sit onto.

I noticed that occasionally, the laser would not come on – however, click the switch again and it was working.  This went on for some time, and then when I had completed the frame and had started cutting the decking boards – the laser wouldn’t come on.  Maybe the batteries had gone flat – unusual since it hasn’t been in use for that many hours.  I checked the batteries and they were looking good, but tried a new set of batteries – and still no laser.

Could the laser have failed?  I couldn’t very well continue to cut without the laser – well, I could, but it would be more difficult since I would have to make trial cuts, then finishing cuts.


Laser battery and switch compartment

The laser battery and switch compartment looks very simple, a little black box with a switch on it, and a wire coming out of it.  The two screws looked inviting, so I got my screwdriver and opened it up.


switched jumpered temporarily

The switch is just a single post single throw switch with two contacts, so i got my jumper wire with crocodile clips and bypassed the switch, and sure enough the laser came on.  Great – except, that I can’t really use it like this – the sawdust would cover the switch in no time at all.  When I fiddled with the switch a little more, I found that the switch would work if I move the bottom contact – so I decided to try a little piece of foam rubber.


foam rubber pushing the contacts apart

Yes, the foam rubber did the job – I made it slightly too big, so it would push the two contacts apart, and then the switch would operate.


the laser is working again

Now, I could get on with my sawdust making – eh, deck building, I mean!  Now, this was a temporary fix.  I called up Makita and they referred me to a service agent.  I called the service agent, and they said that I had to bring the saw in to them to look at.  I said it was just a switch, but they still had to look at it.  Anyway, as it was under warranty – I waited until the decking had been done, for the main deck at least – then took the saw to the service agent.  Unfortunately, they couldn’t look at it straight away as they need to book the technician – I would have to leave it there for 10 days – presumably 10 working days – that was their warranty process.

I decided that since I still had to do some more cutting of timber – that I could either replace the switch myself, or just use it as it is.  Which is what I am doing – the foam rubber is doing its job, only missed the beat once – and I know that Jaycar has a replacement switch for $1.95 so that is what I will do if the switch fails completely.

[Note]  Using a compound saw, or any high speed saw generates a fine mist of sawdust – which is hazardous to your health. You should use a dust mask, at least to P1 rating. I wore a dust mask for most of the cutting, and for the one off cuts – chose to hold my breath which is probably not the best idea. I do realize that I should get some more comfortable earmuffs, since they get hard on the ears when wearing them on top of mask, and safety glasses.

It is a good thing that I bought the sliding compound saw, because I also need to cut some sleepers which are 50x200mm in cross section.