recent amp accidents?

[tedmich]

I am not as up to my elbows in amp work as the pro's here, nor as skilled, so I thought we could recount some recent amp accidents to serve as cautionary tales, I'll start

-just went to add a presence/resonance circuit into my Peavey Ultra+, 3rd prototype, became jaded and DIDN'T UNPLUG AC, connected NFB/Grnd wire to preamp tube board and was about to connect to pot when it slipped and ground wire hit right on mains lug, instantly vaporizing entire tube board ground trace from the pin to the ribbon cable connector...

moral: there is no "safe" part of the amp to work on; shut it down fully for anything!

[soundguruman]

One of my customers spilled beer into his Vox and it wiped 6 stages, all the way to the output transistors.
How long will it be before he sets another beer on top of his Vox? I give it 2 weeks.
Keep drinking beer, you guys are paying my rent. (thanks)

[Chuck H]

I once installed a full/50% power/50%+triode mode switch in a 100W Marshall. After installation I just fired it up, played, flipped the switch and *BLAM* two power tubes of a matched quad up in smoke.

Always do voltage testing without tubes in place after making alterations to the power supply or tube sockets.

[Steve Conner]

I have a commercial 400 watt Class-D power amp module that blew up on me due to poor design. Before the Xmas break I decided to have another go at fixing it. I started with the switched mode power supply which puts out +/-66V. The amp section was bust, so I needed some other load to test the PS, and I used an electric kettle.

The good news was that I fixed the PS, the bad news was that being DC it destroyed the switch in the kettle... no more tea in the workshop!

I also have an old table radio that I hooked up to a time switch, to make a nice alarm clock. I thought I did a good job of restoring it, then one morning it woke me up by exploding and shooting out pieces of capacitor. It was an ancient waxed paper cap connected directly across the B+.

Years ago I was trying to tune up a ham transmitter. I didn't have a dummy load, so I poked a 51 ohm resistor into the antenna jack. It suddenly started to work better than I expected. The resistor puffed smoke, ejected itself from the antenna socket and burnt a hole in the carpet.

I know someone who managed to drop the hot soldering iron on the carpet, and then tread on it with a bare foot while looking to see where it went.

[soundguruman]

I once installed a full/50% power/50%+triode mode switch in a 100W Marshall. After installation I just fired it up, played, flipped the switch and *BLAM* two power tubes of a matched quad up in smoke.

Always do voltage testing without tubes in place after making alterations to the power supply or tube sockets.

Tubes contain smoke. If you let the smoke out, the tubes won't work anymore.