schematics can fins on Jürgen Haible FS1a Frequency Shifter
Issue 1.
after finishing the psu and connecting all potis,jacks.
i got in calibration process 1 a fine TrIangle waveform but without 90degrees phasedifferent.
(dualoscilloskop and separate frequency counter)
by usage the OSC BAL trimpot - i was able to get 2 identical triangle waveforms - but no 90degrees from eachother.
calibration process 1 picture click to enlarge:
Issue - calibrating process 2: failure - no 90degrees different (at 1khz)
after this i tried
racing the signal along the VCO structure:(U9, pin 7 is listed twice)
U8, pin 7: triangle. (You have that.)----yes was a triangle
U9, pin 7: triangle - yes is a triangle (U9 pin7)
U9, pin 1: square wave - yes - but its very unsharp
(at u9 a other new TL072 same result)
so i tried to exchange some resistors described at em forum
em: http://electro-music.com/forum/topic-18587-100.html
http://electro-music.com/forum/viewtopic.php?t=18587&postorder=asc&start=375
I've taken the board out, and have gone over it. No wrong resistors. Bear in mind that this is a copy of Dave Brown's build (and using his BOM), so there are some resistor changes - specifically R2 changed from 51K to 36K, and R51 is changed from 430 to 51K. There is also a 36K resistor added at pin 6 of U1. Would any of these make this effect? (Feel free to chime in, Dave, if you had a similar problem - probably not though)
- R51 muss 51K sein statt 430ohm
- R2 51k zu 36K
- 36K U1 pin6
after this i get this:
(by usage of the sin sharp trimpot - i cannot trim the " waveform like square" to a sin wave.. and its not 90degrees different.
