I think I messed up my Studio .22...help?

[Whoopysnorp]

I just replaced the caps and three of the four LDRs in my Studio .22, and something didn't go quite right. The amp does work, and I actually think the job improved the tone quite a bit, but there seems to be something wrong with my channel switching and possibly the overall volume level. When I switch from the rhythm to the lead mode, the tone doesn't really change. It gets maybe a hair more gain, but that's it. When I switch back to rhythm, the overall volume of the amp swells and then dies back down to normal over the space of about two seconds. The swell actually has a very similar shape to something that happened when switching from lead to rhythm before I worked on the amp--the overall volume would drop somewhat and midrange would dip out of the sound and then everything would swell back to normal. It's like the behavior is backwards now. Maybe I put an LDR in backwards? I didn't think I did...

Two things I didn't replace were one of the caps involved in the footswitch power supply circuit (I didn't have the proper replacement available) and one of the LDRs...here is a picture of that section of the board before I worked on it:

I did not replace the LDR labeled VTL5C2. I ordered that part but it's on backorder. I was also not sure of the value of the LDR pictured on top, so I chose VTL5C1. Perhaps that was wrong? Mesa's schematic didn't specify, so I'm not sure how important it is.

I also relied on the word of a fellow forum poster that this LDR's value should be VTL5C1:

I suppose it's possible that could be in error as well. Can anybody help?

 

[Blueracer]

I would contact tech support at Mesa. They can clarify what the appropriate LDR's for your amp should be. Here is the link with their phone number.

http://www.mesaboogie.com/US/info.html

 

[Whoopysnorp]

You know, after thinking about it, I think I may actually have the LDR on the back of the board in backwards...as it is, its negative terminal is connected to the lead that feeds the positive terminal of the one on the other side, and vice versa. I will swap that after work today and see if that fixes it.

 

[Whoopysnorp]

Fixed it! The LDR was indeed in backwards. The tone is stellar now--totally removed some characteristics of the amp that I wasn't liking. I'm still having the issue where the sound dips a bit when switching from lead to rhythm, but I'll assume that's the fault of the LDR I haven't replaced yet.

 

[stomper]

Most excellent! Not only does your amp sound better. You have the satisfaction of knowing you did it yourself, and can do it again in the future. No small feat. Congrats.