DON’T DO THIS!!

[Pedro Vecino]

Don´t do:
Reinstall a chassis in its amp cabinet (specially in combos) without supervising the aluminum sheet that usually carry glued or stapled. It´s very common when removing chassis that parts of it are dragged, crumpling it and extending areas of its surface towards the interior of chassis. Sometimes even with flying broken parts of aluminum.
I've never had a problem with it but I know it's waiting there

[Gnobuddy]

All I can say is even 40v flashing blue will surprise you when your not expecting it.

About ten or twelve years ago, I was soldering together a rechargeable battery pack using A123 LiFePO4 cells extracted from a 32 volt Dewalt cordless battery pack. Fully charged, each cell has about 3.3V open-circuit voltage.

Unfortunately, I wasn't paying sufficient attention, and my soldering iron momentarily shorted out the six-cell battery pack I was building. (The factory 10-cell pack had internal wires, one of which contacted the iron.)

Not only was there a bright blue flash, there was a hole burned through the soldering iron by the time I had calmed down enough to look at it. An ugly and surprisingly large hole, irregular, maybe 6 mm long in its longer direction.

The iron was a Hakko 936, which has a thick metal sleeve that screws onto the handle and heating element, retaining the removable soldering tip. It was this thick metal sleeve that had the hole burned through it.

Those lithium batteries pack quite a punch!

By the way, those LiFePO4 batteries were much more stable than other lithium chemistry batteries - which is why I was working with them in the first place. I wouldn't open today's less-stable lithium-ion packs.

A123 Corp. was a spin-off from an MIT research project, and for a while, their LiFePO4 cells were the state of the art in both safety and longevity.

-Gnobuddy

[Mick Bailey]

Interestingly, I find SS gear to be more dangerous to work on than tube gear...

Some of the bigger amps work on pretty high voltages; +/-120v and above. So that's 240v DC sitting right there. More importantly, the instantaneous current capacity is far higher than any tube amp can manage due to the much larger PSU capacitance. There's always lots of advice about draining tube amp caps but often SS is disregarded.

[Gnobuddy]

+/- 120 volts? Yikes. Definitely in dangerous territory, and capable of nearly a kilowatt into 8 ohms. I've never worked on an amplifier with that much power.

The current crop of stereo bridged class D driver chips might help a little at less extreme power levels. Operating in bridge mode, you can get 250 watts into a 4 ohm speaker with only a single 48 volt rail. That's low enough to be relatively safe.

-Gnobuddy

[bob p]

+/- 120 volts? Yikes. Definitely in dangerous territory, and capable of nearly a kilowatt into 8 ohms. I've never worked on an amplifier with that much power.

That isn't anything particularly new. Back in the 1980s the Carver M1.5t had a 125V bipolar third rail and was designed to drive an 8R load. It was only rated at 350 W/ch but the specs said it could deliver 1500W on peaks. The pro version of that amp (PM-1.5) was rated for 1200W bridged mode into 8R. So yeah, there have been big-ass SS amps out there for a long time. QSC still makes such monsters.

Some of the high end tube gear has truly insane power supply storage. There are AR amps out there that keep kilojoules on tap.

Be careful out there.

[Mick Bailey]

I had some theatre amps a while back - 5KW with dual mains leads. The speaker outlets were heavily shrouded and there was a warning notice on the shrouds that fatal voltage was present. The owner had used flattened copper pipe to extend the speaker connections outside of the shrouds on each amp "to make things easier". I fixed them, removed the junk and told him to use them like that was not safe. I had one back for a re-work (actually he'd wedged the fans because they were noisy and it was consequently thermalling) and it had the copper pipe back again. We had a run-in when I refused to touch anymore of his stuff.

[Enzo]

The famed Crown MA-10,000. Rated down to a half ohm.

https://adn.harmanpro.com/site_eleme...4_original.pdf

[Leo_Gnardo]

I had some theatre amps a while back - 5KW with dual mains leads. The speaker outlets were heavily shrouded and there was a warning notice on the shrouds that fatal voltage was present. The owner had used flattened copper pipe to extend the speaker connections outside of the shrouds on each amp "to make things easier". I fixed them, removed the junk and told him to use them like that was not safe. I had one back for a re-work (actually he'd wedged the fans because they were noisy and it was consequently thermalling) and it had the copper pipe back again. We had a run-in when I refused to touch anymore of his stuff.

About 20 years ago I was called to a disco. Been there before, the amp/dj system was a wreck, and made worse every time some crack-fuelled dj got behind the turntables. New feature - they'd been talked into buying a new amp for their subs - a Crown Macro 5000 just one pinch below the 10KW beast Enzo mentioned. One new problem, besides now having the ability to fry all the 18 inch speakers they could get their hands on, was the AC breaker popped every time the amp was switched on. Their solution? "We don't need no stinkin' breaker!" They wired it straight into the input rails in their breaker box. It was at that moment I gave up. If there was a fire or stampede at that club due to their screwy decisions, I wasn't volunteering to join the committee of defendants.

[Jazz P Bass]

The famed Crown MA-10,000. Rated down to a half ohm.

https://adn.harmanpro.com/site_eleme...4_original.pdf

Yowsa!
Input : 208V/ 3 phase
Consumption: 16 Amps

That's not an amplifier, it's a welder.

[bob p]

you left out the weight spec. It's 128 lb / 58 kg. It *IS* a welder. It's a good thing that the 3-year warranty includes round trip shipping.

Leo, did the 'little' version of that amp require 3 phase power?