Pitch calibration range issue, with solution

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logarhythm
 
Posts: 1
Joined: Sun Aug 04, 2013 2:05 pm

Pitch calibration range issue, with solution

Post by logarhythm »

Hello x0xers,

I recently built a x0xb0x from a kit and everything was working well, except that the pitch could not be calibrated to reach a full ocatve from a root note when using the transpose buttons. The high note would always be at least a semitone flat regardless of the two VCO trimpots' settings. After some tracing, I saw that IC9's outputs were lower than they should be, even though 5.333v was being supplied. This was still the case even if the output pins were lifted to eliminate the possibility that possible problems in the VCO might be loading it down too much.

It turns out my kit had mistakenly included a 74LS174 instead of 74HC174 or 74AC174. I didn't know until I checked the data sheets, but it looks like the LS version of the part steps the voltage down too much to be a usable substitute. I got ahold of a 74HC174, put it in, and now everything works great and the correct pitch and range can be set well within the trimpot settings. Obviously this is an unusual case but I thought it was worth reminding builders encountering similar issues to double-check IC9.

robboten
 
Posts: 11
Joined: Sat Jul 06, 2013 2:30 am

Re: Pitch calibration range issue, with solution

Post by robboten »

Exactly the same for me. Good to have it resolved after tons of desoldering! :)

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