Newly built crack smoking when powering on

[ncsMD]

Hi everyone,

So I meticulously tested my crack and it passed all of the resistance checks. However, upon powering it on for the voltage check, there is significant smoke coming from the 270 ohm 5W resistors. They also got really hot and so I unplugged the crack ASAP.

This is my second crack build, and the first one I had no problems with.

My only thought is it could be because I have the 270 ohm resistor on 13L and 15L reversed. Could this be the problem? I always thought resistors don't have polarity.

Anyone have any ideas? Please see the attached photos.

https://imgur.com/a/wUePm2b

[Paul Birkeland]

You have a backwards 220uF power supply capacitor.

[ncsMD]

You have a backwards 220uF power supply capacitor.

That was it. Thanks!

[Doc B.]

With the amp off and unplugged verify that that those resistors still measure around 270 ohms. You can measure right across the leads on each one. They are pretty tough and will probably be fine, but when you say smoke I consider the possibility that they got a little cooked and that could increase their resistance.

[ncsMD]

With the amp off and unplugged verify that that those resistors still measure around 270 ohms. You can measure right across the leads on each one. They are pretty tough and will probably be fine, but when you say smoke I consider the possibility that they got a little cooked and that could increase their resistance.

Hey Doc, thanks for the response. I just measured both resistors, and they are both measuring at 250 ohms each. I checked the same resistors on my other crack (which has speedball upgrade) and those measured at 265 ohms each.
Is this concerning?

[Doc B.]

That's fine. If they had been damaged the resistance would have gone way up.