Current Limiting Resistors - A Cautionary Tale

[madbean]

I went through a phase of adding CLRs on power supplies in some of the projects thinking that this is a smart thing to do, especially for people that might use some of the less than ideal, not well regulated supplies that are prone to noise. But, what I'm finding based on some build reports and tech help threads is that I have miscalculated on this. A few people have had problems with burned up resistors due to their projects pulling too much current through the specified value.

So, first off, I'm sorry if this happened to you and it was a total lack of foresight on my behalf. Second, luckily it is easy to correct. So, if you are building a project, and there is a specified 10R resistor on the power supply (would usually come after the 9v input or 1N5817 diode), I suggest you either 1) increase the value to 47R - 100R (and use 1/4W) or 2) just jumper the resistor since it is not essential to the operation. This is only an issue with a few projects that listed a 10R current limiting resistor on the power supplies. Ones with higher values are not an issue.

If you have already built a project with one of these and it is stable, don't worry about it. This is just a cautionary to those few that have had this problem, or might have it in the future.

[bela1961]

Wow, conformation! This happened to me with the dirtbaby, the resistor actually fried black. After a reasoning session with my brain, I decided to jumper and no more problem. I am still having trouble getting effect. I get bypass and un effected through the board. The controls alter the sound but no delay.