Posted by Wayne Parham [ 64.149.49.21 ] on July 31, 2008 at 18:55:30:
In Reply to: Re: Audio Note power transformer posted by Wayne Parham on April 28, 2008 at 13:10:14:
It has been approximately 4 months since I replaced the power supply transformer in my Audio Note Kit 2. So far, so good. I listen to it approximately 4 hours every day and the transformer has lasted just fine. It gets really hot, but it's hangin' in there.
I've been concerned about this amp though, because it regularly blows fuses. Not every day, but maybe once a month. Not enough to say there's a problem for sure, but after a couple times, it's worth looking into. I had time this week to open it up and check everything out, and sure enough, I found a problem that may be the cause of the blown fuses. In fact, in hindsight, I'll bet it's what caused the transformer to fail in the first place. Time will tell.
By the way, I wrote Brian Cherry about this when it happened. He sold me the PS transformer replacement, shipped it quickly, and has provided excellent support. When the fuse blew after that the first time, he told me to check the fuse size, and gave some thoughts about primary and secondary windings, stuff like that. I mean, what can you really do to troubleshoot an amplifier problem over the phone? You really have to get out the scope or meter and check stuff out, without that, it's all just guesswork. But Brian was as helpful as you can be in a situation like this, more willing to help than I think most companies are. Great guy.
So anyway, last weekend I opened the amp and checked some voltages. Found a problem right away - the left channel output tube was biased harder into conduction than the right side, about twice as high. So I retired the amp for a few days until I had time to look into it further. Last night, I had time to fix the amp. A coupling capacitor had become weak and was passing DC, so I swapped it (and all the other coupling caps) with new ones. Now, the bias levels are all correct, so I'll bet the fuse stops blowing every month. 
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