1222 VCO - new build mods/updates
I’m trying to get my head around the suggested mods for a 1222 VCO new build without going too far. this will be my second 1222 VCO after rather a long delay.
Below is my understanding after checking through various posts on the forum and thought it may be useful to get all the suggested working/generally approved of mods all together, Eric kindly originally put together a list of most of these mods a while ago.
MANDATORY (already documented in the 1222 Tuner Module fixes/improvements post from Oct 20)
- Replace R42 resistor with - 1K for CEM3340 or 4K7 for AS3340 or anywhere in between?
SUGGESTED SIMPLE MODS (already documented in the 1222 Tuner Module fixes/improvements post from Oct 20)
-
replace L7805 voltage regulator with a L7808 (more suitable for Arduino Vin)
-
add 10M resistor between pins 4&5 of the 3340 to reduce ringing on square output, although I have also seen 1M resistor suggested for this?
FURTHER SUGGESTED SIMPLE MODS (from the forum but a little scattered about)
-
replace R13 with 200K resistor
-
add 20M resistor between two points marked on board (near-side R26 to far-side R12 or that what it looks like from the image)
- Use a low temperature coefficient capacitor for C6
Does this seem a realistic/accurate summary of mods to include for a new build?
Apologies if this post isn’t formatted very well, still getting to grips with the posting editor
Richard
(reference links below)
https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module-fixes-improvements/2072?u=mtb
https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/453?u=mtb
https://lookmumnocomputer.discourse.group/t/1222-tuner-vco-module/16/605?u=mtb