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 - here its better to use a trimpot 100k and test value above 10K-100K
- 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.
Troubleshooting: 04.09.13
todo:
issue: same triangle at step 1.
test oscilloscope setting for trigger - maybe a triggersetting issue
test:
at U8 pin 1 - must have a triangle COS
at U8 pin 7 - must have a triangle SIN
both must have 90degree !
result:
after checking my oscilloscope settings i found out, its my fault - the channeltrigger settings was set to "dual", needed is here single 1channel..
later i changed back the resistor R51 (board1) ( origin 430ohm, ) to 330ohm so i have a same amplitude..
here correct Oscilloscope settings (click to enlarge)
correct result step1: fine
Step 2 measurement - before R51 changed to 330ohm i used 51K (electro-music-thread -info, was wrong in my case)
Step2 after changing to 330Ohm is like this: fine
