GK800rb can you help?

[warwickhunt]

Hi Dave

I realise that this isn't one of your amps (doesn't even contain a valve ) but wondered if you could give me (or my Sparkie mate to be specific) any pointers!

I have just taken a Gallien Krueger 800rb in part ex. It has a degree of distortion (buzz/fuzz particularly as the note decays but heard pretty much all of the time) which isn't attenuated by reducing the input gain, depressing the -10 db pad, or using basses with lower output. I've also tried plugging into either of the pair of 300watt outputs and the separate 100 watt output, still the same.

I'm aware that each poorly amp could be so for a multitude of reasons but is there a particular area you'd zone in on to check first i.e. output capacitors, some aspect of the preamp, transistors... I'm trying to source the schematic but my mate is prepared to just go through the amp checking tolerances on whatever he can but is there a common failing on solid state amps or a first port of call for distortion problems?

Really appreciate any input.

Cheers

John

[DHA]

[quote name='warwickhunt' post='180973' date='Apr 20 2008, 12:26 PM']Hi Dave

I realise that this isn't one of your amps (doesn't even contain a valve ) but wondered if you could give me (or my Sparkie mate to be specific) any pointers!

I have just taken a Gallien Krueger 800rb in part ex. It has a degree of distortion (buzz/fuzz particularly as the note decays but heard pretty much all of the time) which isn't attenuated by reducing the input gain, depressing the -10 db pad, or using basses with lower output. I've also tried plugging into either of the pair of 300watt outputs and the separate 100 watt output, still the same.

I'm aware that each poorly amp could be so for a multitude of reasons but is there a particular area you'd zone in on to check first i.e. output capacitors, some aspect of the preamp, transistors... I'm trying to source the schematic but my mate is prepared to just go through the amp checking tolerances on whatever he can but is there a common failing on solid state amps or a first port of call for distortion problems?

Really appreciate any input.

Cheers

John[/quote]

Hi John,

it will be a duff component or two, but which one is impossible to tell without a scope and a diagram. Sorry, I can't help much.

Dave

[warwickhunt]

Thanks anyway. I knew it was a long shot!

[oddjob]

John I've got a pdf of the instruction manual and schematics if you want it, pm with your email if you want.

Cheers

Dave

[warwickhunt]

Top bloke is Dave! Schematics duly arrived, ta.

[tauzero]

[quote name='warwickhunt' post='180973' date='Apr 20 2008, 12:26 PM']I have just taken a Gallien Krueger 800rb in part ex. It has a degree of distortion (buzz/fuzz particularly as the note decays but heard pretty much all of the time) which isn't attenuated by reducing the input gain, depressing the -10 db pad, or using basses with lower output. I've also tried plugging into either of the pair of 300watt outputs and the separate 100 watt output, still the same.[/quote]
Have you tried running the effects send into line-in or effects return on another amp? You could at least establish whether the distortion is happening at the front end or the rear end. Conversely, you could run from an effects send on another amp into the effects return on the 800RB to check the power section out.

[warwickhunt]

Cheers mate. Not thought of that one

I'll give it a blast and I've got the schematic so things are looking up. I know it isn't anything major as it still works fine.