Unlock the VDO A4 bike computer to A8

How to pay 600 rubles and get functionality for 1200? Probably everyone knows the way to “upgrade” the bike computer - put 2 magnets on the wheel and the speed doubles, but we will go the other way. We double the number of functions of the bike computer with one movement of a screwdriver.

While working at VeloDrive Corporation, I often rummage around in accessories and noticed that for some cycle computers, the form of release, the case and segment cells on the display are the same, only the markings and, accordingly, the price differ. For example, the VDO A4 bike computer carries the declared functions:

Current speed (0 - 199.5 km / h).
Distance counter (0 - 999.99 km).
Total Distance Counter
Watch (24 hours)

While his older brother, more expensive in the price list, promises us:

Current speed (0 - 199.5 km / h).
Distance counter (0 - 999.99 km).
Total Distance Counter
Clock (24 hour mode)
Average speed.
Maximum (peak) speed.
Trip timer (0 - 23:59:59).
Index of average pace (shows the current speed above or below average).

Twice as many features. But, you see, it is unprofitable for the manufacturer to run two different conveyors for the same bike computer models that differ only in the data displayed on the screen and the formulas for their calculation in microcircuits. Therefore, they are riveted on one elementary basis, and a cute Chinese woman (or Thai, or Malaysian) decides to become an A4 or A8 computer at the final stage of assembly packing the entrails inside the case.

So, we take the patient from the warehouse and retire to the back room with the camera. For the operation we will need:

1) A slotted screwdriver wide
2) A cross screwdriver
3) A slotted screwdriver
4) Hot-melt adhesive or sealant

First, open the case. It is better to do this from the edge, there the screwdriver most confidently enters the groove. Do not be afraid to push it, the body is glued with hot glue and you have to break the internal legs-position fixers.



After opening, we see inside the printed circuit board fixed with five screws. We remove the hot spots of hot melt glue around the edges, they may interfere in the future to close the case.



The caring engineer Liao left the instructions on the board itself for the lovely girls on the assembly line. From it we see that in order to turn the A4 bike computer into the A8 model, we need to remove the jumper S1 (DEL) and leave the jumper S0 closed (CLOSE).



It is time to find the jumpers. When removing the screws, be careful, right behind the board is the display and its contact group. I recommend raising the board by lightly pressing the “slot” screwdriver in the opening between the bottom (lone) screw and the edge of the case, as the board is still held on by hot glue. There is nothing to damage on this side of the board.



This is how the board looks after removing the screws. Immediately set aside the housing with the display to the side, removing the remnants of hot melt adhesive.



Board closeup. The jumpers we need are located at the bottom left. On older models of bicycle computers, they were simply flooded with solder, now they began to put conductors, for ease of removal.



This jumper is removed simply. We put the board on a flat, soft surface, take a slotted screwdriver and, having set the tip on the side of the letter S, we easily hit the end of the screwdriver with your palm. 1-2 strokes and the jumper removed.



Next, we carry out the assembly in the reverse order, carefully tighten the screws so that the display contact is established, close the case and coat with hot glue all around.



As you can see, in addition to the main functions, speed, distance per trip and odometer appeared: travel time, average and maximum speed, as well as an icon showing above or below the average speed, we are driving.
All.