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Trackball Mouse Hack - Horizontal Axis Troubleshooting
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stimpyjoy:
Ok, so I'm home and I've done some tests. Here's what I found:


--- Quote from: stimpyjoy on August 11, 2014, 05:47:15 pm ---I thought I had eliminated trackball error as a possibility by proving that either trackball axis can drive the cursor vertically when wired that way.

--- End quote ---

I was wrong. :-[ The horizontal optical circuit on the trackball is not working. The LED is not visible through my cell phone.  The vertical one works.  I don't know why I thought I had it working, but it doesn't now. In fact, when I switched the wires, I got NO cursor movement.


--- Quote from: NickG on August 11, 2014, 10:55:41 am ---looks like your H2 trace is cut, check continuity to the IC.

--- End quote ---

I still don't see a problem just by looking at it, but there was a problem with my blue "H2" wire soldered to the mouse board. No continuity. I replaced the wire and now I can get either X or Y cursor movement but only from the one side of the trackball. I initially discovered this when I held the wires directly to pins 10 & 11, 12 & 13 on the IC. 



So now it seems my problem is a busted optical circuit on the trackball. Any idea what my next step should be?
PL1:
Viewable angle on the LEDs can be tricky-- compare the voltages on the two trackball PCBs to be more certain.

1. On the horizontal trackball PCB,  connect the black lead of your multimeter to a ground like the frame of your computer and use the red lead to check the voltages at the following points:

-- +5v should be 5v and Ground should be 0v (never hurts to double check things like this, even though they're probably not bad)

-- H1 and H2 should change between high and low as the encoder wheel turns.

2. If H1 and H2 are good, skip to step 4.

3. If H1 or H2 is bad, disconnect it somewhere between the trackball PCB and the mouse PCB and test it again.

In troubleshooting, this is sometimes referred to as "divide and conquer" or "splitting the circuit".

If the line tests good after you split the circuit, the problem is somewhere between the split point and the IC.

4. Check data line voltages at IC pins 10 and 11 -- should be the same results as step 2.

5. If one data line voltage is bad, there is a problem somewhere along the trace for that line -- clean well around all the areas you've soldered with a Q-tip/isopropyl alcohol and examine the PCB closely with a magnifying glass looking for shorts/opens.

6. If it still doesn't work, unplug the trackball (no power going to it) and use your multimeter in Ohms/continuity mode to check that you don't have:
-- an open trace
-- a short between two traces


Scott
NickG:

--- Quote from: stimpyjoy on August 11, 2014, 05:47:15 pm ---Thanks for the replies.  This is my absolute first foray into electronics, so please forgive my ignorance.


--- Quote from: NickG on August 11, 2014, 10:55:41 am ---looks like your H2 trace is cut, check continuity to the IC.

--- End quote ---
Can you actually see that from the photo? I'll check continuity when I get home.

--- End quote ---

Yes, in the bottom left photo it appeared to be lifted/cut near the thru-hole where you desoldered the LED.
PL1:

--- Quote from: NickG on August 12, 2014, 01:27:42 am ---in the bottom left photo it appeared to be lifted/cut near the thru-hole where you desoldered the LED.

--- End quote ---
Agreed.

Also, be sure to clean all the solder splatter off the whole PCB using isopropyl alcohol and a Q-tip, an old toothbrush, or an acid brush.




Scott
RandyT:

If you can get X or Y output, but only from one side (axis) of the trackball, it's pretty much a confirmation of a dead optical PCB.  The optical PCBs, specifically the opto-sensors, are for the most part a consumable item.  The IR LEDs in these things have a much shorter life than a normal LED, and will dim over time.  Usually, the first indicator is erratic behavior, and then total failure isn't far away.   That's not to say the IC, or some other part on the board isn't the culprit, but the IR LED's are usually the weak point.

Replace the PCB (might as well do both of them, but that's up to you) and it will very likely solve the problem.
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