Gallien-Krueger 700RB MKII Hit By Lightning!

In a few instances, poor wiring in the venue has killed sound equipment.  More rare is the instance when you are actually playing and lightning strikes!  If you are Angus Young, being “Thunderstruck” is OK, otherwise, it is NOT COOL.  This Gallien-Krueger bass amp was soldiering away at church when a nearby lightning strike ended the Praise and Worship portion of our service.  Could the Unbrokenstring Crew help?

Let’s start off with some gratuitous tech porn.  This unit has a built-in DI box with a balanced output.

We have all sorts of tone-shaping capability.

The separate outputs for tweeters and woofer are nice.

The effects loop connectors in are front, as well as an easy means to attach a tuning pedal.  The POWER / PROTECT LED is RED until everything stabilizes, then turns green;  And, of course, the ubiquitous ON/OFF switch.

Here is a block diagram for those who are unfamiliar with all the architecture and features of this amp.

These speaker outputs connect the combined woofer and tweeter signals to a cabinet.  The AC input is self-explanatory.

These Neutrik connectors allow access to the separate tweeter and woofer amps, if that works with your cabs.

The fuse was blown, but I smelled something burnt.  The main circuit board needed to come out.

We had a blown fuse, so I did some troubleshooting before replacing the fuse and powering up again.  The filter capacitors were slightly swollen, so I checked them for ESR.

The ESR meter showed that these caps were OK.

The only visual sign of anything burned was this residue from an arc flash. Little bits of metal are burned and blown around the vicinity of an electrical arc.  The electrical surge of the lightning transient plus the conductivity of the ‘smoke’ from the arc flash blew the fuse.  All this happened during the lightning strike.  Fortunately the circuit board was not pitted.

The case was pitted.  This is where the metal in the arc flash came from!  We’ll clean this up and then replace the fuse.

Everything worked well.  The unit was returned with a very modest repair bill.  We have yet another happy customer!

Thanks for reading all the way to the bottom!

Contact – David Latchaw  EE

cell – 281-636-8626