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HD500 expression pedal not working properly
by anelson86 on 2012-07-07 19:01:04

So I have an HD500 that is about 8 months old.  This week I started to notice that the expression pedal is not properly sweeping through the full range.  What is particularly frustrating is that it often will only go from about 0-20%, so I am stuck in the middle of playing and can't get my volume pedal to go above 20%.  Adding to the odd behaviour is that after being powered off for a few hours, when turned on the pedal will work normally for 2-3 minutes.  After I have used it for a few minutes the problem shows up.

I did the calibration procedure laid out in the document here: http://line6.com/support/docs/DOC-2223When doing the step using footswtich C to check the scaled pedal value, I get 0 at the heel position, and then it will scale to about 60 and then jump to around 140 when I'm at the toe position.  If I set the pedal at a certain level and then leave it, the scaled value will not remain constant but rapidly jumps around to different values - faster than the LCD can resolve the digits.

Anybody have any idea what might be wrong or any troubleshooting steps to fix it?

Thanks!



Re: HD500 expression pedal not working properly
by jimsreynolds on 2012-07-08 02:20:30

If you are certain that you have followed the calibration sequence correctly then you could do what this guy dd and clean the sensor.  Beware of the potential warranty issues ... http://line6.com/support/message/350381#350381



Re: HD500 expression pedal not working properly
by anelson86 on 2012-07-08 15:23:48

Thanks for the suggestion.  Instead of actually taking it apart I went ahead and used compressed air to blow down the hole where the sensor is.  That didn't do anything and the problem is still happening.  It's really weird that everything is ok for the first few minutes and then it gets messed up - it seems like it is maybe a software bug?



Re: HD500 expression pedal not working properly
by jimsreynolds on 2012-07-08 17:02:53

Not beyond the realms of possiblity.


Suggest you re-flash (keeping presets) and then do a global settings reset and calibration.

Bearin mind that if there is some kind of sticky goop on the sensor that the air-jet may not clear it.



Re: HD500 expression pedal not working properly
by anelson86 on 2012-07-08 18:24:17

Tried the re-flash, global reset, and expression pedal calibration twice - no dice.  During step 5 of the calibration the scaled pedal value only goes from 0 to about 70.  Initially when it is put all the way to the toe position it pops up to 145, but then quickly goes to about 70 and wobbles around between 60 and 80.

I'm a bit leary to open the case up and do anything since it's probably still under warranty, so I may take it in to a service center this week.



Re: HD500 expression pedal not working properly
by anelson86 on 2012-07-08 19:01:19

So in lieu of popping off the whole back and removing the circuit board I decided to loosen the bolt of the pedal itself with the allen wrench that came with the board.  I took the bolt out and the pedal off and then blew off the sensors again with an air can.  They look completely clean - however, the white reflector on the bottom of the pedal that allows the sensors to work has a scratch right across the middle.  Perhaps this is causing the problem?  I'm thinking once the pedal gets to the right distance that scratch is right in line with either the light source or sensor and is causing the light to not be aimed back at the sensor, resulting in a mis-read of the position.

The only thing that this wouldn't answer is why it works for 1 or 2 minutes before getting messed up.  Perhaps the light source is a laser diode (which it looks like) and takes a minute or two to settle into it's operating wavelength so the issue isn't immediately apparent.

Either way, I'm thinking I need to get a new reflector for the bottom of the pedal - not sure how that could have gotten scratched except from the factory.



Re: HD500 expression pedal not working properly
by jimsreynolds on 2012-07-09 00:27:56

Warranty call is looking increasingly like a smart move

The sensor is indeed optical.




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