Peavey KB4 Keyboard Amp Disintegrating

This Peavey keyboard amp works intermittently, but the modular AC outlet has completely come loose from the rear panel. Can the Unbrokenstring Crew fix this?

This unit is pretty cool, with a built-in luggage roller and extendable handle as standard equipment from the factory.

 

The modular AC plug was covered in RTV rubber.  Was this a user ‘fix’ or did it come from the factory this way?

 

Fortunately, all the electrical conductors were insulated.  Otherwise, we would have sparks.

 

User controls are on the top.

 

The ground polarity switch is a throw-back to the days of two wire electrical cords.

 

A simple mixer is integrated into the unit.

 

Name, rank, and serial number, please.

 

The panel layout allows for some space for the handle.  Good Job!

 

We removed the head from the cabinet,

 

Here is our intermittent.  This power resistor had broken free from its solder pad.

 

A circuit board trace had broken.  An Exacto knife clears away some of the solder mask to allow for a repair.

 

This crack was very small, so a good solder jumper is all that is needed here.

 

This unit appears to have been wet.  Do you see the minerals left behind after the water evaporated?

 

Here is another little blob of mineralization.  This may have been from solder flux residue left after the assembly was manufactured.  Some fluxes turn white in the presence of water.

 

This screw was loose inside the grille.  This screw holds the loudspeaker in place.  This is not good.

 

Most of the screws were loose.  While we have this unit on the bench, we should be sure that the loose screw is not a sign of a more sinister problem lurking with this unit.

 

Here is the loudspeaker in this unit.  Nice!

 

My guess is, humidity has softened the baffle upon which the loudspeaker is mounted.  These Tee nuts will be removed and new holes drilled in the baffle in different locations.  The Tee nuts will be reinstalled and we should be Good-To-Go.

 

Some black nail polish will camouflage the new fastening hardware.  You do have black nail polish, don’t you?  Doesn’t everybody?  Hint: This also makes good thread locker.

 

OK, now for the IEC power jack.  This unit has mounting ears, so we won’t rely on friction or glue to keep it in place.

 

As an added bonus, this IEC jack has a built-in noise filter.

 

The hole in the chassis was enlarged to accommodate the new jack.  This hand grinder is adequate for the job.

 

Yep!  Just fits.

 

Now we will bore the steel panel to accommodate the mounting hardware.  This will be SO much better than glue!

 

This doesn’t look too bad, does it?

 

All of the original wiring goes straight onto the new IEC jack.  This is better than factory!  Hot glue was apparently used at the factory to secure the switch and the old IEC jack to the rear panel.  So that answers that question.  Shame on you, Peavey!

 

Here is one last look of the internals before we reassemble the head.  The mixer is at the bottom and the power amp and power supply is at the top.

 

This unit is literally ready to roll!

Thanks for reading all the way to the end!

CONTACT – David Latchaw EE
281-636-8626

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