Gallien-Krueger backline 600 problem

stepashka · #1 02-14-2011, 01:49 PM

Hello!
I have a problem... GK BL600 works fine on low volume, but distorts on high ones. Heater fan stops in half second after turning power on.
I send couple of letters to GK support (I am living 9000 miles far from USA), but got no answer.

How can I turn cooling fan constantly on? Did anyone have schematic of this amp?

Sinclair · #2 02-15-2011, 01:13 PM

The fan only spins if the amp gets warm - that's normal. No need to turn it on constantly.

Let us know your settings (f.e distorted vs not distorted).
Most of the people use the volume, boost and master in a wrong way. Keep the volume below 12 o'clock (10-11). If you need more -> turn up the master. Set boost in conjunction with master to taste. Boost has a great influence on overall volume...

craig.p · #3 02-15-2011, 01:30 PM

Even under low/moderate (but steady) volume, the fan should spin slowly. Check to see that yours is doing that. If it stops right after you turn the amp on, but never starts up again, especially at moderate volume, then yes, you might have a fan problem or a sensor problem.

To add to what Sinclair said, use the NORMAL channel, not the overdrive channel.

FWIW, I have my master set at about 3:00, and I control the volume with the LEVEL-A knob.

Also, start with the BOOST control completely off.

ygdartis · #4 02-17-2011, 11:01 AM

Hi,

I got the same issue on a MB150E i brought in Cambodia ; Once here, nothing to do to set it up properly ;

I was thinking the plane trip mistreated it, but i slowly went through, understanding how to use the 3 knobs (volume, Boost, Master).

Volume is working quite logically as the gain knob of a mixing board, (level in), so if too high the signal will get distorted, and you increase the distorted signal with the master, the boost fonction, naturally making the distortion fatter. Volume (level in) is actually really sensitive (or sensible, sorry for my english writing), especially if you get in active, so the reason of the attenuator which is on the MB150E. Don't really know about the BL600, but same brand so,..

There are some weird things though ; like strange loop when i switch a 2nd speaker and swith the Lift/ground on ground,.. But it seems this brand gets a subtle electronic, i guess i'll read the electronic plan and the manual again ! Good luck with yours .

tocs100 · #5 02-17-2011, 11:44 AM

Does your amp distort on the speaker out or d.i. out?

Make sure you're on the clean ch.
You have 4 gain stages:
1) start with it on active to ensure no overload at the input
2) input gain can be brought to about 6 for active basses, 10 for passives
3) Boost is post-fx-loop gain to make-up for pedals with low output levels
4) master comes last and you shoudn't need it higher than 2 for bedroom levels

Mine has a problem in that post-eq d.i. is distrted and hissy no matter what I do. However, the pre-eq d.i. (direct from the input) and amplified output is fine.

stepashka · #6 03-10-2011, 01:50 AM

Quote:

Originally Posted by craig.p

Even under low/moderate (but steady) volume, the fan should spin slowly. Check to see that yours is doing that. If it stops right after you turn the amp on, but never starts up again, especially at moderate volume, then yes, you might have a fan problem or a sensor problem.

Fan never starts again, that is the problem.

Amp wasn't OK, I replaced couple of resistors, because they were burned out. Without this replacement amp distorted on clean channel (direct out sound was OK).

After that amp began to work fine on low volumes. On higher ones - it became distorting. If I slow down volume after upping, I distorts too.
To stop distorting, I need to turn amp off for couple hours, and turn it on again on low volume.

I think, this is sensor, or something close to it, problem.
And I see no another way, except cut off sensor (or shortсut it), or to replace amps fan with PC fan and small 12V PSU.

craig.p · #7 03-10-2011, 04:48 AM

Or you could remove the fan altogether, and attach one externally to the top of the fan vents. You could use a box fan that runs off low voltage supplied by a cheap "wall wart"-type power supply. You can keep it in place with velcro strips. I believe airflow direction is down, i.e. the internal fan pulls air in through the top of the cover and exhausts through the front vents.