Ambika: 20p caps (C26/C27) either side of crystal

I don’t have enough to do all 6 voice cards but I have some 18 or 22. Presumably they’ll do as long as I use the same on both sides of the crystal?

Should I also use the same pair or each one of the voice cards or does it not matter?



Id does matter and if they are to far off it won’t do. Theres a certain reason for the parts having different values…
So use the same Value on both sides, please. The Caps are roughly 10% off the desired value, while having a tolerance of about 15-20% so it should work although it isn’t guaranteed.

Its not a matter of whats on the board, its a matter of the installed crystal that depends not the caps. Mine for instance wouldn’t work with 18p or 22p, as they need 32p.

Actually, two 18p caps were supplied with the voice card kit from Olivier, even thought they’re marked as 20p on the boards so it can’t be that critical :slight_smile:

Sorry for asking

It was just your youthful exuberance that got me in old pseudo wise teaching Mode :wink:

Fair enough :slight_smile:

Am now tempted to put some headers where those two caps are so I could swap them out easy. Is this a known issue with the voice boards - you say yours didn’t work until you’d done a bit of trial and error?

By the way, I’m talking about the SMR-4s.

Just put them in, and if they don’t work then desolder them again. There is no magic in desoldering a 2-legged component…

Im building my voicecards and on the SVF BOM it states 22pF for those 2 , so Im putting those in and we shall see what happens. ( I have the 20 Mhz Quartz also)

The quartz is 20Mhz, but the decisive question here is what pF value it needs to oscillate properly - the Reichelt ones need around 30pF, while the Mouser ones need around 20pF. The exact value can be found in the respective data sheet!

Hence my original question.

Ill build just one first and figure out the best caps to use.

reminds me back when my dad told me to solder a socket for each BC238C . . . .

Wise words…

not really; a Transistor was 17 Pfennig, a Socket 25 Pfennig…

But that was the kind of german “Wertarbeit” this generation has been taught :wink:

“not really; a Transistor was 17 Pfennig, a Socket 25 Pfennig….”

Sorry, my ‘wise words’ comment was 100% sarcasm :slight_smile: