Dropped Ampeg SVTIII Pro Bass Amp Quick Fix

This Ampeg hybrid amp was dropped.  And of course, it quit working.  And, of course, the guy who borrowed it was the guy who dropped it.  Can the Unbrokenstring Crew get it going again before the friendship gets damaged?

The exterior of the unit is in great shape, because it was in a hard sleeve that absorbed most of the drop.

The handle is now useless.

The rack ears (those aluminum angles) broke away from the sleeve.

The rack ears are pop riveted into the sleeve.  The guy who dropped it said that he would fix all that… just repair the electronics.  Got it!

A quick tour of the front panel, from left to right.  The midrange frequency selector has five discrete positions, which moves the center frequency of the midrange tone control up and down in frequency.

The graphic equalizer is switched in and out by the button below the mute button.  It took me a few seconds to figure that one out.

And here we are at the right end of the front panel.

This panel handles the internal switching and foot switch duties.  The fan and filter are to the left of this picture.

The name, rank and serial number dog tag is here.  Interestingly, this unit has binding posts as an option for speaker connections.  More goodness from St. Louis Music!

The toroidal power transformer dominates the interior view.  The emitter bias resistors rate their own heat sink, in the path of the cooling fan air.

All of the tubes in the preamp were brand name except this one.  Which tested fine and works well in this circuit.

The real issue with this amplifier is that the jolt of the drop unseated this cable connector.  This is easy enough to fix.

This amp is operating at 450 watts into 4 ohms.  I think we fixed it!  And the owner will be none the wiser!

Thanks for reading all the way to the bottom!

CONTACT – David Latchaw EE