HORRIBLE SQUIELING NO INPUT signal

[stringking]

I just tried out my a12 and it squels like a pig with no input i was using an at4033 , i tried swapping around the j1 j2 jumpers with no avail , funny thing is though i plugged in a sm57 and it worked like a champ no hum buzz or anything so maybe its in the phantom power , if anyone could help this newbie out i would greatly appreciate it lance

[stringking]

by the way im using the cmmi and sc25 rig on this one

[tpryan]

So you've built an A12KF with the CMMI8-PCA input transformer? If so, just remove J1 and J2. Make sure J3 and J4 are jumpered correctly (pins 2 and 3 shorted). Jumper J5 but not J6. Measure the voltages at the input XLR with the phantom turned on but nothing connected. You should have 0V between pins 2 and 3 but 48V between pins 2 and 1 and pins 3 and 1. Also, make sure you have the right caps installed at C1 and C7. Let us know what you find.

[stringking]

oh man i dont think i have 5 jumpered and i misspoke myself i have j1-2 removed and j3-4 are jumpered correctly im going to try jumpering 5 real quick THANK YOU

[stringking]

HOLY CHRIST IT WORKS , AND I DIDENT FRY THE BOARD FRY MYSELF OR BURN DOWN THE STUDIO TIM THANKS FOR THE QUICK RESPONSE I WAS GROWING AN IRISH SIZE ULSER WONDERING WHAT I MESSED UP ANYAWY THANKS A LOT . LANCE