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Weird La3a problem, please help.
Old 20th November 2007
Gear Maniac

Thread Starter
Weird La3a problem, please help.

I have two old La3a's, one of which, approximately 3 minutes after powering up, starts to oscillate and the vu meter starts rocking back and forth while the vu light is dimming simultaneously. This doesn't stop until I switch the unit off. Trouble is, it only does this in my studio. I've already sent it to an experienced tech twice and he could not reproduce this fault, even when leaving the unit switched on for hours at a time. He tried it in various places. Back at my studio, it happens every time I switch it on. Even when nothing is connected to it. I also tried all available power outlets in my house...

Could this be a power issue? I find it really strange, since this is the only unit playing up. The second La3a is fine and all my other outboard too. Whenever I take it out of my house, it seems to work just fine. (?)

Help and pointers appreciated.

Thanks for your time

Old 21st November 2007
Lives for gear

Get the tech to come and look at it in your studio.
Try it on a 'Variac' and reduce / increase the mains to see if it can be persuaded to misbehave.
Matt S
Old 21st November 2007
Gear Maniac

Thread Starter
thanks matt

i'll get a power conditioner with constant voltage output in sometime next week to see if this helps.


Old 21st November 2007
Lives for gear

Your unit is certainly faulty so a conditioner is not really a good long term solution.
As long as the mains is within plus or minus 10 percent it should work perfectly.
Borrow a unit by all means but proper repair would be better.
Matt S
Old 22nd November 2007
Gear Maniac

Thread Starter
hi matt

it is not intendend as a long term solution and i did try to have it repaired, but it behaved well at the 'doctor's'. i just want to find out if my power is problematic and how i can reproduce this in other places so that someone can fix it.

do you have any ideas, what the fault could be? the 110/220v switch was intermittent and thus bypassed, way before i got the unit.

since it affects the audio, the vu meter and the light, i guess it is a powersupply related problem. since it happens exactly 3 minutes after powering up, it could also be a thermic problem or some sort of feedback building up.


Old 24th November 2007
Lives for gear

Maybe the I/O cables or mounting it in the rack is causing some weird problem? I'd pull it from the rack, disconnect the audio cables, then run it for a while and see what happens. If the problem recurs then maybe you should look at your AC power...but somehow I doubt that's the problem.

If the power selector was bypassed, that's a bit of a red flag. Maybe a combination of faults is causing this problem to happen at your place but not elsewhere.
Old 24th November 2007
Gear Maniac

Thread Starter

it happens in and out of the rack, audio connected or disconnected, on all the power outlets i have in the house. however, yesterday it worked for more than two hours without playing up. then i switched it off, and back on a while later. this time, after about 20 minutes, the fault was back, but in a changed appearance. when it happens now, the vu meter doesn't rock back and forth anymore, it just sinks down to -10dB gain reduction) and sits there, and the vu light isn't affected.

i'll keep an eye on it and see how it develops.

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