Classic gear from yesteryear; vintage audio standing the test of time.
Message Sort: Post Order or Asylum Reverse Threaded
low 12AX7 filament voltage in my Fisher X-100-A amp
108.237.120.79 |
||
Posted on December 2, 2016 at 22:55:38 | ||
Posts: 70
Location: No. California Joined: January 20, 2006 |
Hi, I'm restoring a Fisher amp and the cathodes of the output tubes (7189's) are connected to three 12AX7's in series + a 22 ohm resistor (and a 2.2 kohm resistor and a 200 uF,50 volt cap are in parallel with that). Two of these tubes are in the phono stage and the other is the tone circuit. Anyway, each of these 12AX7's only has 9 VDC dropped across the filament (pin 4 to pin 5). This seems awfully low to me. I'm asking because one of the tubes does not seem to be conducting as much current as it should be, there is barely any voltage drop across one of the plate resistors. Should I try upping the voltage a bit across these filaments? |
wow, thank you! nt, posted on December 7, 2016 at 20:32:19 | |
Posts: 70
Location: No. California Joined: January 20, 2006 |
nt |