On page 3 towards the bottom, section 4. Setup Hints - Set all trimmers as indicated on Picture 1: Main Board Schematic
Not much of an alignment guide!
Sorry, "Setup hints" chapter remained unfinished (hence the
TODO), fine alignment steps are completely missing - it is not simple to formulate them properly and there are already copies of original EM alignment procedures available online, which can be used by experienced builder, so I did skip it for the first draft..
First bullet is there just to quickly move you into the working area, where you should already get some flanging, but fine adjustments should be done yet. This can be especially useful when you are not equiped with proper tools like signal generator and oscilloscope and your only tools are DMM and your ears
RT1 1k CCA 50%
RT2 10k CCA 5.5K
RT3 100k CCA 7.0V
RT4 10k CCA 4.7K
First, you probably know but just to be absolutely clear, CCA = circa =
approximately (I am not sure how common is this acronym around the world actually).
Now,
RT1 (clock noise cancel trimmer) mixes two signals so I say here adjust it to approximately 50% (half of the trim range) so the mix ratio is 1:1.
RT2 (feedback trimmer) and
RT4 (clock trimmer) are configured as variable resistors, so I just say adjust them to given values (measured by DMM on fully populated board, that is how I have measured them - this is not precise method, but good enough for
approximate)
RT3 (BBD bias voltage trimmer) is configured as a voltage divider for the bias voltage on BBD (TDA1022) input - so I say here what voltage should be at it's output (measured against the GND) - but actually, 7.0V is value for 10V supply which I have used, so adjust it to 70% of your supply voltage (e.g. 6.3V for 9V supply). This trimmer should be precise and multi-turn type, because for the fine adjustment the sweet spot range is very narrow.
T.
