my lovely xoxbox has started to make a noise all the time, when no notes are playing. it’s slowly been getting worse over the last year or so.
it’s like the OSC is being permanently triggered, or the envelope is stuck open. it’s a few years old, and works perfectly in all other respects.
I tried contacting the guy who built if for me (Andy Pledger at Synthetic Music Systems), but I’m not sure if he’s around any more.
Can anyone recommend someone who could fix this issue?
You could maybe try this guy?
http://labs.fluctus.org
I have only used him once, to repair my Moog MF104SD, but he was very nice, and seemed experienced.
it´s in Germany and not UK but might he can help you too.
http://www.x0xsh0p.de/
btw. is / was your xoxbox right in tune? I have a Modemachines XOXMK2 and it´s soo out of tune when playing over different octaves 
This should be easy to fix, even with no diy skills or equipment.
All you need is a phillips head screwdriver and some kind of tuner (unless you are confident in your ears - i just used the tuner in Ableton, but a guitar tuner should work).
Touch something metal to discharge any static charge. Take the back off your x0xbox and look for the 2 trimpots labelled TM4 and TM5.
Centre the Tune pot and power up your x0x in keyboard mode.
Hit the bottom C on the keyboard of the x0x and note the frequency output.
Now hit the high C and again note the frequency.
Adjust TM5 and alternate between the high and low C until the high is giving you exactly 1 octave, or double the frequency in Hz that the low is giving you.
Once you have done this, hit the low C and adjust TM4 until you get a C note (I think the lowest is C1 - 65.4 Hz).
Your x0x should now be in tune.
See here for more info:
http://www.ladyada.net/make/x0xb0x/fab/vco.html
thank you for the links
when i bought my xoxbox-kit i made a big mistake when i soldered this thing - a beginners failure - i soldered and soldered like a child beeing so happy and i did not read the instructions from ladyada.net. so it happend that some parts won’t work and the current-flow is broken
on the other hand i soldered and measured all my modular kits parallel to this project very successfully
thanks for the tips - fluctus labs sounds perfect - and less than one mile from my house 
This should be easy to fix, even with no diy skills or equipment.
All you need is a phillips head screwdriver and some kind of tuner (unless you are confident in your ears - i just used the tuner in Ableton, but a guitar tuner should work).
Touch something metal to discharge any static charge. Take the back off your x0xbox and look for the 2 trimpots labelled TM4 and TM5.
Centre the Tune pot and power up your x0x in keyboard mode.
Hit the bottom C on the keyboard of the x0x and note the frequency output.
Now hit the high C and again note the frequency.
Adjust TM5 and alternate between the high and low C until the high is giving you exactly 1 octave, or double the frequency in Hz that the low is giving you.
Once you have done this, hit the low C and adjust TM4 until you get a C note (I think the lowest is C1 - 65.4 Hz).
Your x0x should now be in tune.
See here for more info:
http://www.ladyada.net/make/x0xb0x/fab/vco.html[/quote]
thanks mate! may i will try out but still have some warranty on the xox
update…
i’ve narrowed the issue down the accent level knob. if the knob is turned all the way left, there’s no hum. all the way right and there’s a really loud hum all the time, when no notes are playing.
no response from fluctuslabs, can anyone recommend any other uk-based synth repairers?
thanks
I bought a machine from Andy Pledger recently (Very Happy with it), you should be able to find him via his ebay account.
ah, nice one - i’ll try that.
Does the pitch change if you trigger a new note in keyboard mode? The VCO on an analog synth is always oscillating so it could be the VCA staying open if so. In which case it could be a faulty BA6110 or one of the associated transistors.
i found andy via one of his recent ebay auctions and have made contact again. thanks duncan!
thanks man - will try this. andy is going to have a look at it for me, but this would be a good pre-test 
Hey, just wondering do you have a contact for Andy? Cheers
DM me, I have one from a few years back. No idea if it’s still active though…