[sdiy] capacitor ID

[Tony Clark]

   Hi Ruud!

> with a TL071cp and 2 capacitors with "1.35"

   Hmm...doesn't sound like a standard value cap to me!  I would be 
inclined to guess it as 1.35uF, but the nearest standard value you can 
buy (at least here in the states) is 1.2uF or 1.5uF.  Are there any other 
features you can tell us about it?

> some resistors (210/2.1k), 2 very small capacitors with "33" and "22" on it,
> and 2 small ones with "105" on it.

   These are in pF, so 33pF, 22pF, and if I read that correctly, 1.0uF (a 
bit strange to go up to 105, must be a metallized film?).

> it doesn't seem too hard of a job since it's basically copying what's in
> from of me.. but i have a hard time with the capacitor values. is there an
> exact way to determine this? how do you know if something is measured in uF,
> or pF? what would these examples above be?

   Capacitors can be frustrating, but the general rule of thumb is that 
if it does NOT have a decimal, it is pico-farads, but if there is a 
decimal, then it is in micro-farads.  Others will notate what value it 
actually is.
   Also, newer capacitors use resistor-like notations such as the 103 or 
104 (0.01uF and 0.1uF respectively), but on older parts, you are more 
likely to find 10,000 or 100,000 as well as .01 or .1 instead.

> and second: the lm741 in the original is an 8 pin ic. the one i ordered is
> an lm741ch, which is round. is this the same thing? how do i know the pin
> numbers?

   Look for the prong on the bottom edge of the can.  This points to pin 
number 1.  Then if you go clock-wise around (looking at the bottom of the 
can), you'll get the rest of the pins 2-8.  You can easily group the two 
sets of four pins so that the part will fit into a standard DIP 
footprint. (however you might double-check the datasheet to make sure!).
   Also, some cans may have a dot on the bottom that will also point to pin 
1.  And some cans are REALLY Nice in that they actually do preform the 
leads into the epoxy to conform to the DIP footprint!

   Hope that helps!

   Tony

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