Anyone got a LAB1000?

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   Has anyone here got a LAB.Gruppen LAB1000 amp? I've got one which I'm repairing at the moment and need to know something about its behaviour.

Other than the faults which I've already fixed, when you switch the amp off, the fans continue to run and slow down as the capacitors discharge (if this is normal, it seems like a good idea - keeps on cooling the amp) but I still get output (if I leave the gain up and keep feeding a signal in), which gradually degrades as the reservoir capacitors discharge. This seems a bit odd on a professional, high quality amp like this - I would've thought there should be some kind of muting circuit which kicks in when you switch the power off.

Also, there doesn't seem to be any kind of power up delay, but there aren't any bangs or thumps or anything, so maybe it doesn't need one.

I've got a service manual for it, but it's not particularly informative. Just parts lists, schematics and PCB layouts. Nothing like the detail which Crown, C-Audio and others put into theirs.

Can anyone shed any light on the lack of muting?

Cheers,

Wrighty

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Wrighty Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 17 April 2004 Location: Devon Status: Offline Points: 1801	Post Options Post Reply Quote Wrighty Report Post Thanks(0) Quote Reply Topic: Anyone got a LAB1000? Posted: 20 June 2007 at 11:48am
	Has anyone here got a LAB.Gruppen LAB1000 amp? I've got one which I'm repairing at the moment and need to know something about its behaviour. Other than the faults which I've already fixed, when you switch the amp off, the fans continue to run and slow down as the capacitors discharge (if this is normal, it seems like a good idea - keeps on cooling the amp) but I still get output (if I leave the gain up and keep feeding a signal in), which gradually degrades as the reservoir capacitors discharge. This seems a bit odd on a professional, high quality amp like this - I would've thought there should be some kind of muting circuit which kicks in when you switch the power off. Also, there doesn't seem to be any kind of power up delay, but there aren't any bangs or thumps or anything, so maybe it doesn't need one. I've got a service manual for it, but it's not particularly informative. Just parts lists, schematics and PCB layouts. Nothing like the detail which Crown, C-Audio and others put into theirs. Can anyone shed any light on the lack of muting? Cheers, Wrighty

gingerbiscuit69 Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 23 September 2005 Location: United Kingdom Status: Offline Points: 2540	Post Options Post Reply Quote gingerbiscuit69 Report Post Thanks(0) Quote Reply Posted: 28 June 2007 at 11:29am
	im no expert but it sounds like the 'softstart' circuits gone (which delays output when turned on, and cuts its once powers off). good idea with the fans using the capasitor charge if its meant to do that, surely after turning off an amp, it would get a heat spike from the thermal energy still inside and the lack of cooling?

Wrighty Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 17 April 2004 Location: Devon Status: Offline Points: 1801	Post Options Post Reply Quote Wrighty Report Post Thanks(0) Quote Reply Posted: 28 June 2007 at 4:48pm
	Yeah, if I could work out which bit was the soft start from the schematic, I could check it! The service manual has zero description of how any of it works. As you say, using the reservoir caps to make the fans run on is a good idea. I always let the amps run on after a gig anyway (with crossover muted), but an in-built system which is effective even if the mains plug is pulled is an excellent idea. There's quite a bit of energy stored in those caps too!