bad distortion

[andywho]

just wanted to put a link in this forum to a something I posted in general discussion that touched on (among other things) one of my A12 channels:

http://www.seventhcirclestudios.com/SCA/phpBB/viewtopic.php?t=744

hope that's cool...thanks again for any help in solving this.

[andywho]

here's the quote from my original post: "one of my A12s outputs a badly distorted signal. I've triple checked the voltages (I'm running the SC25s both at 18V) and switched out the op amps between the two to no avail. for the life of me, I can't find any difference between the good A12 and the bad one (except for I have no header at J6 on the bad one--the kit didn't come with one, and I figured it wasn't necessary seeing as I wasn't going to be doing anything with J6 anyway(?)). I'm not sure where to start looking for a fault."

In browsing the forums, it looks like I may have done something very stupid: the R16 that came with my A12 was damaged (bad threads), so I had to wait while a new one came. during that time, I fired up the channel to do the initial power-up and testing, with nothing at R16. whoops.

is there a chance I damaged something while doing this? like I said above, I switched the op amps between channels, and it makes no difference--hopefully meaning I didn't damage them. but something else perhaps?

[tpryan]

With the op-amp removed, power off, and R16 fully CW, what resistance do you measure between U1, pin 6 and U1, pin 2? With R16 fully CCW?

[andywho]

thanks tim...here's what I get for both the working channel and the broken one:

good one:
R16 CW: 20.35K
R16 CCW: 9.94K

bad one:
R16 CW: 20.33K
R16 CCW: 9.95K

in both cases it takes a minute or so for the values to get there.

[tpryan]

Is the distorted signal loud or soft? Do you have any way of generating and observing a test signal, as with a DAW?

[bradb]

What resistance do you measure at J6 between your good A12 and bad A12?

Just curious.