A12 started acting up on gain step 7

[Bhudie]

Hello,

I've built 2 A12's and and 2 N72's a couple of years ago(love them to death...), and all builds went great until now. Just recently my second A12 has been acting up. It works fine on all gain steps except step seven. When I set it to step 7 I get loud crackles and pops.

I'm looking for some assistance troubleshooting this. I reheated all the solder joints from R1-R13, and this didn't fix my problem. I was thinking that because it only happens on step 7 that it would likely be a problem with those resistors. Is that a fair assumption? Is the fact that the problem only shows up on the one gain setting a clue to any other areas on the board where my problem might be?

I'm about to get my DMM out and start tracing, but I'm a novice at troubleshooting these boards, so I thought I'd post here and see if anyone could point me in the right direction first.

Thanks in advance,
Aaron