Silverface Twin Needs Help

[wingobingo]

Have a 1972 Silverface Twin. Over the last several months the amp has lost volume and is sounding more "harsh" than usual. I usually use the vibrato channel so I tried plugging into the normal channel - loss of volume is even more. Ideas as to where to start?

[Lonely Raven]

Have a 1972 Silverface Twin. Over the last several months the amp has lost volume and is sounding more "harsh" than usual. I usually use the vibrato channel so I tried plugging into the normal channel - loss of volume is even more. Ideas as to where to start?

When was it last serviced?

Loss of power typically sounds like it simply needs a tune up. Tubes are good, right?

[wingobingo]

It hasn't been serviced in at least 4 years - I use this for a second project that I'm involved in. I can start with tubes, however I don't have any idea how to set the bias on this one.

[jelle]

My suggestion is to take it to a tech. Are you near NJ/NYC?

[wingobingo]

In Pennsylvania - might take it to George Alessandro - who built another amp for me. where are you located

[philo43]

Check the fiberboard that the components are attached to. It can warp and cause cracked solder joints where the component leads connect to the board. It's a pretty common condition with silverface amps that have several years of use. Take a wooden dowel and prod around on the components and leads and listen for pops, it will most likely reveal the culprit. Better yet, try reheating all the solder joints. Of course, this should be done after checking all the tubes by substituting known good ones, one-at-a-time.