| Author | Message | ||
     Giordano da Silva (macg1) Username: macg1 Registered: 06-2009 |
Are the 112 Sixty-five's with the PI 12AX7 self biasing or cathode biased amps or will i have to adjust it upon replacement of power tubes? | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
They should be checked, especially with todays production tubes. They are a adjustable bias amp with the adjust wheel on the main circuit board, closest to the transformer end. There are two pots, one for trem trim and the other for bias adjust. By the way, these amps have over 700v on the plates so, besides being careful, only adjust to 22-23mA PER tube. That 1/2v at point Y stuff isn't really accurate enough. | ||
| Giordano da Silva (macg1) Username: macg1 Registered: 06-2009 |
Thanks Mike, I have adjusted bias before in Fender amps but got accustomed to cathode bias as of late. I have a new bias meter coming and will certainly check the values. Thanks for the quick reply. |