Hello Gang, In an effort to increase the receiver sensitivity on my finally restored SB-101.. I recall that there was a certain mode to change out the 6AU6 rf amp tube with a 6HS6. Iam pretty sure this was in a QST in the late 70's, but my collection of QST's stop at 1973 and go down... Well I bought a NOS 6HS6 and just plugged it in, didn't appear to change things much.. Perhaps certain pins need to be rewired? Any help appreciated.. Al fritsche@msn.com KD5CML -------------------- Hey Gang... didn't take long to get my answer on the 6AU6 to 6HS6 conversion. Mister Chuck Penson, said just plug it in... sensitivity goes from1 uv to .035 uv , no wiring changes. Boy am I glad about that... I will probably have to realign as the preselector positions changed.. Done tryed it.