DUH!

[riz]

Working on a Champ today. Could not for life of me get it to bias to full dissipation, even with a 260-ohm cathode resistor on the 6V6 it would only get up to 8 watts diss., and 15V on the cathode, and the voltages were low everywhere. Today was my first day using a light bulb limiter and 1:1 isolation transformer, together... Works great for it's intended purpose, but that really screwed me up for a while once I replaced shorted/fried components and was up and running! Did not think about the limiter dropping that much voltage, variac maxed couldn't get it over 300V B+... But still my mains read 146V AC to ground at the fuse (because of the iso trans), even when the heaters got under 5v playing with the variac! WTF!! Sure sounded good though! There's something to that "brown sound" thing. Glad I figured out what the hell was going on. Duh. Just had to share.

[Gunny]

I had a similar experience but on a solid state Vox amp where the torroidal PT had failed. Upon restart after installing the new PT, I used a light bulb limiter. I forgot to disconnect it and plug in directly to mains power. The amp worked but sounded like crap. It was late on a Friday night. Guess I was tired. Of course it sounded just fine without the limiter...that's my Doh! or Duh! story : )

[riz]

Yep it had been a long day for me, too, and a reminder that it was time to get away from high voltage! I'm in an accelerated intermediate learning phase right now, so by the end of the day my brain is mush! Lesson learned...?!

[Gunny]

The other thing I've done - at least 3 or 4 times - following repairs to tube amps, is forgetting to plug the tubes back into their sockets before powering up and testing. Not much noise from the amp without the tubes!

I know electronics, my given profession, but it's a good thing I'm not making a living fixing amps and telling these kind of stories.

[riz]

At least most of the "errors" we admit to making in this thread err on the relative side of safety, from the human perspective! I mean, I WAS hooked up to a limiter and an isolation tranny! Now, had I hooked this amp up to mains with a low-value cathode resistor, that could have been another story for the tube. OH, another DUH! The 1k I bought at the store was a mix-up-- 1R!!! Story over for that tube... another lesson. What I am gaining from the DUH moments, is a steadily building experience base to guide my procedure, in conjunction with steady repetition. In the past this was a very occasional hobby, and I would forget much of what I learned between projects. Now I'm getting more into it daily. Putting your hand on the stove really is the only way to learn sometimes! That reminds me of another DUH...