Servex Wheel Alignment Laser Repair (With Video)
Laser technology is used in many different fields – Medical, communications, printers, optical disk drives and the list goes on.
In the automotive field, lasers are used in lighting and also steering wheel alignment equipment, amongst other things. It is a laser wheel aligner that is being looked at in this article, namely the Servex LX7-3000. This item was brought into the lab after someone else had tried to carry out a repair and actually made matters worse.
Initially, they believed that the fault was a loose charge socket or damaged wiring at the socket. A new socket had been installed, but with solder dobs the size of cricket balls! These backed onto the battery pack and created a short.
During fitting of the socket, the customer told me that he thought that he had damaged a track and installed a bypass wire (green wire) to repair the track. At this point, I think this is where the magic smoke left the unit! After that, the wire had fallen off.
Testing of the rechargeable batteries showed that they were totally drained. I wasn’t sure if they would recuperate after being charged.
After a careful examination of the wire that had been installed, I discovered that he had soldered it onto the wrong side of a capacitor, therefore creating a dead short! After testing the charging port, a short within the socket was observed. A decision was made to replace the socket with a socket disassembled from a cordless phone charging station. After unsoldering the charge port, the short disappeared, confirming my diagnosis.
Installation of the port included careful use of glue. This method was chosen as the original port seemed to be held onto the circuit board with some sort of adhesive. The outer housing of the laser was checked to make sure that it did not foul on the charging socket terminals. Just to be sure, continuity of the housing was checked and found not to be made of metal, so shorting of the terminals would not be an issue.
Once the glue had dried, wiring from the socket was installed besides the original wiring from the battery pack, making for a neat connection. The charging power supply was connected via an isolation transformer.
Although the batteries originally were dead flat, an overnight charge brought them back to life. The green ‘full charge’ light was illuminated. However……..when the power pack was turned on to provide power for the laser, nothing happened. Clearly, more damage had been done.
I had spent some time checking all the components again and finally compared the readings from the other power pack the customer had provided. The only faulty component that could be found was the IC. This IC was a HEF4001B, which is a quad 2-input NOR gate and it was no surprise that it had lost the magic smoke, considering what had previously been done to it! In the meantime, I tested the batteries on the spare power pack. The ‘Good One’ had batteries that were dead flat as well as one that had almost a dead short, with a resistance of up to 5.8Ω! I would be recommending to the customer that all batteries in that pack be replaced.
The new IC arrived was ready for installation. However, I did find it hard to create enough heat to melt the solder for all legs of the IC. It had also been soldered both sides of the IC.
I decided the easiest solution was to be a bit creative and although it seemed a little rough, the technique worked well. After cutting all the legs of the IC with side cutters, each individual leg was easily removed as normal.
Installing the new IC was a simple task. After, the flux was removed and the area cleaned using Isopropyl Alcohol.
Several wires were correctly fitted to bypass the damaged tracking that had been burnt as a result of the shorting of the socket, the original bypass wire, batteries and IC.
Finally, after all the diagnosis and repair, the power pack came back to life. The socket had come dislodged and needed to be reglued.
Once I had confidence that the power pack was operating correctly, it was time to connect it to the laser.
The customer was happy with the result and he could confidently hand the unit back to his employer. I did recommend that the batteries be replaced in the other working unit that he had brought in.
Another job off the list!
If you are interested in this repair, you can see a video on my channel following the link below.
This article was prepared for you by Mark Rabone from Australia.
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Note: You can check out his previous repair article below: