10
Troubleshooting
Some tips:
• No output. Power is on, but power LED is off and tubes do not light up.
Mains fuse is out. Replace fuse as per instructions on page 9.
•
No output. Power LED is on and tubes do light up normally.
Check if preamp comes out of MUTE after 30 seconds.
Check input selector setting, input and output wiring; if all seems to be OK check power amplifier.
• Noise coming from one channel.
Noisy tube. First swap the 12AX7 tubes left to right. If noise follows tube swap, than you have
found the problem tube. If noise does not follow, swap the 12AU7 tubes left to right.
• Hum coming from one channel.
Check rectifier tube 5AR4: swap L to R , if hum follows tube then replace faulty tube.
• Noise/distortion coming from both channels.
Tubes may be in need of replacement. Read page 8 for tube basics and replacement options.
If you try these possible solutions and problems persist, contact us or your local distributor for further
investigation.
Tube Selection
While matched tubes are not a requirement, it is still recommended if you want to get the very best
results. You can get the very best in replacement tubes as well as rare vintage NOS (New Old Stock)
tubes from us and other parties if you wish to upgrade. In the USA, Upscale Audio's inventory of New
Old Stock tubes is the largest you can find. Elsewhere, independent suppliers can assist you to make
your best choice.
PrimaLuna
®
ProLogue Three