Hello, I recently acquired an old 1960s Airline 9017a 2x12. Currently I have no sound coming from it except a slight hum, tested from all inputs. All tubes light up except for the 6EU7. My first thought was to replace that tube with a known good one, but unfortunately that did nothing. I am not great at reading schematics at all so I am hoping someone here can assist. I've attached it as PDF. I don't currently have any spares to test this out so am going to have to order new tubes once I have some idea. My next logical path based on my lack of skill would be to replace the V4 and V5 12AX7s and the V11 6DR7 as they appear to be directly connected to that 6EU7. Am I totally wrong or does anyone have any good suggestions? I would prefer not to have to spend money on a tech if I don't have to. Thanks in advance, you wonderful people!
Is the standby switch turned on? It should be turned off.
I wouldn't replace a tube unless you're certain it's the problem.
The 6EU7 only works the reverb so not to worry about that one. Voltage checks on the valves would be the first place to start.
Unfortunately the schematic is not the most accurate!
Unfortunately the schematic is not the most accurate!
I have tried all combinations with the two switches and still just have the faint hum in all positions, unfortunately.
The only tool I have is a multimeter. Can you point me to a good resource to start with on how to check the voltages?
Tube datasheets are available from triodeelectronics.com
The voltages on the tube pins should be within the limits on the datasheets.
Be sure to read the safety sticky thread above the tube amp forum, about checking voltage safely above 24 Vdc. Short form, one hand at a time, ground of meter alligator clip connected to analog ground point. No jewelry on hands fingers or neck. Wear safety glasses against explosions of caps or other components.
I fix amps with multimeters (digital and analog), load resistors instead of speakers, and transistor radio as a signal source. Analog meter is for checking music flow through the circuit after the DC voltages are correct and still no sound. 20 VAC or 2 VAC scale.
Best of luck.
The voltages on the tube pins should be within the limits on the datasheets.
Be sure to read the safety sticky thread above the tube amp forum, about checking voltage safely above 24 Vdc. Short form, one hand at a time, ground of meter alligator clip connected to analog ground point. No jewelry on hands fingers or neck. Wear safety glasses against explosions of caps or other components.
I fix amps with multimeters (digital and analog), load resistors instead of speakers, and transistor radio as a signal source. Analog meter is for checking music flow through the circuit after the DC voltages are correct and still no sound. 20 VAC or 2 VAC scale.
Best of luck.
The schematic you included has lots of voltages to check. The tubes are all highlighted in yellow...if you look immediately next to the yellow marks, most of the plate voltages are given. For the outputs (v7-v10), pin 3 should be 375 VDC, pin 4 should be 372VDC, and pin 8 should be 30VDC. This is with no input signal. The other tubes are documented likewise. Like most pro schematics, redundant values have been omitted, so you have to fill in some blanks by tracing wires.
The schematic has been somewhat redrawn to save space, especially in the preamp. It doesn't look quite as clean as a Marshall or Mesa schematic, but it does look accurate. You shouldn't need a whole lot else (besides skill and maybe parts) to get this beast roaring again.
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