ooops!!!

[Neil Groves]

Just an update on my component sourcing, i thought you guys might be interested in:

After spending much time searching for my bits, i wanted to recommend 'small bear electronics' and 'futurlec', i found quite a few companies that stocked the obsolete parts that i needed but i would have had to have made minimum order of 75-100 which was way beyond what i needed, the companies above do 1's and 2's off if thats all you need, the postage came to more than my parts though.

Oh yeah, when my LM3900 arrived, i was so excited, i went straight to my workshop and swapped out the LM324, i powered up the circuit and ........nothing!!! after scoping around for a few mins, i realised i had laid out my veroboard for the LM324 and they arn't pin for pin replacements.....DOH!

Now i have to start again and lay it all out for the new device, i hope i havn't destroyed it! although i did buy 3 of them just in case.

Neil.

[janneman]

Neil, thanks for the heads-up.

BTW The 3900 is a very different animal than the 324; are you aware of that?
Apart from the pinout, you can not just swap the two in a circuit.
For one, the 3900 has one input that is very low impedance and is meant as a current input, while the 324 is a 'real' opamp with two high impedance inputs. But there's more.


jan didden

[Neil Groves]

Thanks Janneman, i was only aware of this after i put the circuit together thinking at the time they were compatable lol

Neil.