Alesis QS8.1 troubleshooting help?

[Philip Santiago]

Hi,

my QS8.1 has been giving me problems lately. the volume im getting (even with the slider pushed up high) is very low, so that i have to turn up the amplifier very loud in order to hear it well, and at this point the sound is very tinny and bad. the problem is also intermittent, this happened to me a year and a half ago, and then the problem disappeared. the unit was working well over the weekend but now has gone back to the state described above.

i have tried reinitializing and this did not work. i have also made sure that when i turn on the instrument that all the sliders and the modulator are pushed down to 0. my keyboard is almost 12 years old and has never been serviced, and i have not had a dust cover on it during the whole time i have owned it. could it be some sort of problem with dust on the inside of the unit interfering with the contacts for the volume slider or the modulator?

any ideas for things i could try would be much appreciated.

thanks very much,
Phil

 

[happyrat1]

Pick up some contact cleaner at Radio Shack and squirt a little into the slider.

 

[delaware dave]

While it is exhibiting the problem check and see if the headphone jack is working normally. If it is then a short term solution would be to use the headphone jack. Go to radioshack and purchase a TRS male to dual female TS jacks. If you typically output mono then a male TRS to female TS converter jack. I had a 6.1 that had faulty jacks and used this solution for a year before I retired the keyboard.

 

[happyrat1]

Plugging a headphone out jack to an amplifier line in jack is a great way to blow out both devices.

Impedances and signal levels are nowhere even close to a match.

 

[delaware dave]

As I posted earlier I did this for one year with a 6.1 and it didn't impact the keyboard nor the amp in the least. As the signal is hotter the main volume will need to be adjusted down on the keyboard until the desired output level is achieved. This same subject has been covered in multiple forums. It's also been a solution for electro 2 owners for driving a leslie/sim due to its low output from the mains.

 

[happyrat1]

Regardless of whether or not you were lucky enough to get away with it for a year, I also ran output from an old Casio keyboard to a line level mixer a few years back and it also worked for me for a few months, until it blew out the headphone jack and sound became horribly distorted.

Headphone levels are ~ 1Vpp to 5Vpp and headphone impedance is ~40-50 ohms.

Line level inputs are ~ 10 mV to 100 mV and line input impedances are approximately 10 KOhm to 100 KOhms.

Your mileage may vary, but in the long run I can guarantee something's going to fry with that kind of mismatch.

 

[delaware dave]

It was recommended as a short term solution, not a permanent fix. He still needs to get the keyboard fixed; but short term it's a workaround.

 

[happyrat1]

Actually it would be workable if he can find a 10 - 20 dB attenuator to stick in the middle of the circuit to balance out the excessive voltages and currents that are being delivered. In most Google searches, however, I have yet to find one that's designed for that purpose. If anyone finds one link it in here. All I've managed to find off the shelf are XLR Mic attenuators with XLR form factors. Nothing in the 1/4" phone jack category.

 

[happyrat1]

Incidentally, my first reply to this thread still applies. From the sound of it, the intermittent scratchiness and volume fluctuations are most likely the direct result of a dirty volume potentiometer and a simple squirt or two of contact cleaner and lubricant will probably fix the problem for years to come.

The youtube video I posted applies to cleaning rotary pots, but sliders are essentially the same devices with a slightly different mechanism.

Open up the panel and squirt a few drops of contact cleaner into the pot and work it back and forth a few times and then reassemble it and power it up and it should work good as new.

And it wouldn't have mattered if he had had a dust cover on the keyboard or not. Over 12 years of use, grime works its way into the mechanism and the internal resistor, be it carbon compound or the more expensive wire wound type, oxidizes on contact with air and airborne moisture and creates a noisy, resistive contact that interferes with normal function.