Ok, so this may go down as the most traumatic day in my life. Let me put this in context;

1. I show up at school, and find a form crucial to my graduation that was supposed to be submitted in November, hiding in a pile of papers on my desk...:tears:
and I literally sprint through the pouring rain to the grad office where I am assured that it's just a minor technicality. :banana:

2. The Canuck's game...talk about false hope, after watching 50 minutes of the Duck's run circles around our local ringette team, :boring: Then a late goal to tie the game, some unlikely (and undeserved) confidence to push it into overtime. :banana:
Then our backup goalie Danny Sabourin starts the overtime in net?!?!? :yikes:
Makes some terrific saves, Luongo returns to carry the team through the period, then possibly the worst goal to end a series EVER. :cry:

3. I come home, dejected, and notice that the one meter light on my AU-20000 is on, as I had been testing the inputs as per Orcinus's suggestion and I somehow left the thing on before I went to the game... As I get closer, I don't smell anything burning...but there's a significant amount of heat emanating from the uncovered top so I quickly go to shut it off. But wait a second...what happened to the protection light? Thinking it's burnt out, I turn off the amp, then pull the bulb (the faceplate is off) to check it. Plug it back in, and turn the amp on again, just for kicks. Lamp lights up, then...clicks off?????? :jawdrop:

Turn on the discman, plug in the headphones...OMFG!!!! :music:
Grab a spare speaker, wire it in...:music: :music: :music:

Hit the meter selection button, left meter is still not functioning, cycle it a few times, it starts to kick, cycle it a few more times :banana: :banana: :banana:

Honestly, the audio gods have smiled upon me, and I don't know why...maybe as a consolation prize for the Canuck's losing? Maybe for the pittance I paypal'd them last night? Maybe for simply NOT jumping into the amp with my meter and iron and asking you all for help first?

Still, theres lots of heat coming off the front bank of heatsinks (rear bank don't seem hot at all...) offset is +30mV on the right, +100 on the left, left meter seems to deflect slightly less on the power output, but I can't tell with the cheap speakers I've got at the low volume it's at...so it's definitely going to need some work...

Anyone offer any explanations???? Uncharged caps? Re-melted some cold solder joints??? I don't know how, or why...but man o' man, this may be the strangest day I've had in awhile.

And even stranger...I borrowed a movie from my friend when I left...and I'm not even joking...George A. Romero's Land of the Dead...:scratch2:

The GF seems to have hidden the camera on me...pics will come!

How come my banana's ain't dancin'???? They shoud be doin the FREAKIN CHA-CHA ACROSS THE WHOLE SCREEN!!!!!!

:yippy:

It's Alive...IT'S ALLLIVEEEE!!!!
http://www.homevideos.com/freezeframes7/youngfrank72.jpeg

now clean and tune it up so itt stays alive :yes: they are sweet amps when they are working right.

Better not go to sleep tonight. You don't want to wake up and find that it was a dream.

- Pete

You know, at one time the church would have you believe a donation would save your soul. I'd say a donation to AK is far more likely to save your gear. Congrats, and hope your audio luck holds!

Bias is way off, or the amp is oscillating. Check the bias setting.

Bias is way off, or the amp is oscillating. Check the bias setting.

That was one of my guesses, that the bias was off, but as the amp warmed up, it came into range. I will do that ASAP, tomorrow morning, I'm going to let it cool off and see what happens when i start it cold again. Does this rule out transistor problems, or might I have a lazy one or two still kicking around in there?

Ok, so I woke up this morning, turned the amp on, everything still worked to my surprise! Bought some test clips after I finished up today, went out for dinner, came home, turned it on to test the bias and...nothing. Protection light is staying on again :scratch2: .

Tested bias right:41mV left: 28mV, not bad but adjusted both to ~35mV, can't test offset, don't even know if setting the bias is effective when in protect mode. So I'm guessing the bias is OK, even though it's cold, so scratch that...next, oscillating? What does it do, what causes it, and how do I test for it?

Better luck next time I guess...:tears:

Steve

Steve IMHO if it is broken and has a bout of immaculate conception, it will only be a matter of time before the disappointment returns. This from past experience.

Bias is absolutly affective when it is in protection. If too far off it will put it into protection. You need to check offset at a point before the speaker/protection relay. Odds are it will be way high on one or both channels.

I'm fighting with an AU-7900 at the moment with similar symptoms. It alternates between 45 volts and 22mv offset. Currently everything checks good but half the time it is out of protection and stable and the other half of the time it is in protection with near rail voltage on the output. I think you are looking at something similar. Get a can of freeze spray and see if anyting reacts to a good chilling.

- Pete

Bias is absolutly affective when it is in protection. If too far off it will put it into protection. You need to check offset at a point before the speaker/protection relay. Odds are it will be way high on one or both channels.

I'm fighting with an AU-7900 at the moment with similar symptoms. It alternates between 45 volts and 22mv offset. Currently everything checks good but half the time it is out of protection and stable and the other half of the time it is in protection with near rail voltage on the output.
- Pete
Hi Pete
May I ask if it's the left channel :scratch2:

So I let her warm up (in protection) this morning while I went to do some yard work, came back in, protection was off, amp was barely warm as it's sitting on it's side at the moment. So went in and re-measured bias: 31mV-right 91mV-left, though I had set them cold to ~35, reset them both to ~35mV, set offset to <15mV on both channels. Everything is playing fine, I can shut it off, and turn it back on and protection relay clicks in within a couple of seconds. With my limited knowledge of circuit and schematic reading, I wouldn't be able to pinpoint where I'm supposed to be reading what voltage anyways. Still going to take it in, but I'm off to the interior for a couple weeks to chase fishermen (and fisherwomen) so it's gonna have to wait. So I'll just enjoy it for the day on my awesome studiocraft (aka BOSE!!!) test speakers.

Cheers all!

Steve

P.S. Totem, don't plan that get-together until I get back!!!

:beerchug:

Sten, yes it's the left channel. Does it make a difference?

- Pete