Koch Loadbox dead :(

Ruben · Post by **Ruben** » Sat Mar 04, 2006 12:37 pm

Hey guys,

check out these pictures here: http://www.mijnalbum.nl/Album=IZHAVFJF

Those are 2 X 16 Ohm Loadboxes I used on my 100 Watt '67 Super Bass with a 16 Ohm checkerboard cab. Amp & Cab are still fine, no damage.

Maybe due to the high Voltage outpuit from the amp (540 V.) the amp was actually a 150 Watt amp????

These boxes can handle 120 watt....

Can that be?

I lowered the voltage to 480....so that the amp will run somewhat easier.

Anybody knows what caused this?

By the way: I cut the resistor myself to see what was underneath, but I couldn't read the value because of the melted board

shakti · Post by **shakti** » Sat Mar 04, 2006 3:39 pm

Did you use both, or just one?

This is the older version of the LB, right? Looks like that in the photos. I have an 8 ohm and a 16 ohm, great boxes. I think I prefer them over the Hotplates by a hair, at least for moderate attenuation.

Anyway, I think the 120W rating is only peak rating, and not continuous. A 100-watter at full tilt will put out 150W peaks if not more. The LB is not built to take a 100-watter. I use mine with 50-watters.

Are the boxes still working? I thought I toasted mine with a Super Bass a while back when I saw smoke coming out and smelt the bad smell of a burnt resistor. Turns out I only toasted a resistor in the headphone circuitry, so that's the only part not working now. At the time I was running it straight through though, no attenutation. Did this happen while you attenuated the amp? I can't remember exactly, but I *think* the resistor I toasted was in the same place as yours.

Anyway, if you want to find out, I got good help from a guy called Edwin Kool (I think) at Koch. Try to email them, might take a while to hear back, but they were very helpful to me and emailed me a schematic (which I lost in a computer crash...why I moved to Mac...but I'm rambling)

Ruben · Post by **Ruben** » Sat Mar 04, 2006 4:59 pm

Thanks man.

A friend of mine is going to repair it. It already smelled BAD during gigs and now finally one of reristors burned he he. I used them seperatly of course not at the same time

I already mailed Koch. They told me, at the time I was looking for the Loadbox, I could actually use it with a 100 watter.....

Anyway the guy who's going to fix it is going to put a bigger resistence in it. See if that works, I'll keep you posted!

shakti · Post by **shakti** » Sat Mar 04, 2006 5:25 pm

Are you sure it's a good idea to put in a bigger value resistor? And is the unit working as it is now, or completely dead? I would advise you to get something that is intended to work with 100-watters. When I asked them, they told me it was not built to take on a raging, overdriven Super Lead or Super Bass...

Ruben · Post by **Ruben** » Sat Mar 04, 2006 5:56 pm

They said to me I COULD use it on a 100 watt amp.....

So, what should I do now? Put a bigger reistance in it? How do I do that and what valaues?

Ruben · Post by **Ruben** » Sun Mar 05, 2006 7:33 am

Can anybody help me finding a schematic for the Koch LB 120 loadbox?

Thanks!