No Noise nor randomness

[MFallise]

Good day,

First tests on my newly built Turing looked fine until I discovered that actually, randomness was missing. After double checking soldering, re-calibrated and some additional tests, here is my status:

• Sequencing is fine (length selection behaves correctly, clock ok)
• Scale => OK
• CV OUT => OK
• PULSE => OK
• Lock trimmer => looping Ok (see below)
  But...
• Nothing comes out of Noise OUT
• Randomness (12 o'clock on trimmer) keeps looping on the same sequence without any variation
  So...
  I've could create a "randomness" by patching a LFO in the CV IN, then, wiggling the trimmer around the 12o'clock creates some "fake" randomness (actually following the LFO) and can lock (full CW ) on a sequence. But that's not what the baby is made for, right...
  This looks like close to this issue: Turing machine not random. Also, no noise #97
  Based on this thread, I've checked the schematics and this really looks like local to the noise generator circuit. As I see, there could be only 2 causes for my problem: either the 2N3904 or the TL074... IMO, assuming that I get a correct CV OUT which also uses the TL, it seems most unlikely that it's damaged (am I correct ?). So, all my suspicions focuses on the 3904...
  Could you suggest a workaround or a way to verify my assertion ?

Cheers,

Mike

[TomWhitwell]

Hi, sorry to hear that, no noise will mean no randomness so that sounds right

[MFallise]

Thank you Tom for this quick reply. Do you think of any advice to troubleshoot/ locate the issue ?

[MFallise]

Hi Tom, ordered a new 3904, and happy to say that everything works like a charm since then. Meanwhile I ordered the Voltages expansion and, boy, this is some nice piece of hardware!
So this issue was relying on a overcooked transistor and is now closed for me. A hint for amateur electricians like me: Be very careful when soldering transistors, they are very sensitive to high temperatures.

Cheers,

Mike