One for the amp/electronics guys.. Can you solve this one?!?

[NEWTON IN ORBIT]

Just a couple of things. First off, the missing ground pin is a HUGE FREAKING DEAL.

Second, this is a tube amplifier, NEVER RUN WITHOUT A SPEAKER LOAD. Ever.

The speaker was, or was not connected when this happened?

This can fry up your output transformer. Did you replace the fuse and does the amp work at all?

Remember, everything modern has a chassis ground, or most everything. Basically, you effectively grounded your amp via the patchbay, and probably all the rest of the gear connected to it.

Was this a transformer based DI box, or a unit that takes 48v or battery?

I'll let somebody more knowledgeable with tube gear take it from here, but man...you gotta have stuff grounded, particularly vacuum tube gear running at high voltages like that. Firstly for safety's sake, and you are lucky you are not injured or dead. Secondly, many pieces of gear in your studio rely on ground for noise rejection. If I have a rack unit that is using a wall wart, sometimes I will even ground it's chassis.

Old vintage amps and PA's were death traps with the two prong plugs. There are many stories (and a couple / few on here @ GS) about people being electrocuted, and either dying, or being in a coma for weeks with severe burns all over their body.

You are also very lucky it didn't take out all your gear downstream, ala your converters etc., and other things connected to your patchbay.

In short, you are lucky that ground on the other gear was secure.

Ground lifts = quick and dirty band aid, and basically are a bad way to go about eradicating noise.

Get that plug fixed immediately, if not your amplifier in general now.

Again, maybe a vacuum tube guru can chime in.

Be careful,
john

[skills]

Originally Posted by NEWTON IN ORBIT

Just a couple of things. First off, the missing ground pin is a HUGE FREAKING DEAL.

Second, this is a tube amplifier, NEVER RUN WITHOUT A SPEAKER LOAD. Ever.

The speaker was, or was not connected when this happened?

This can fry up your output transformer. Did you replace the fuse and does the amp work at all?

Remember, everything modern has a chassis ground, or most everything. Basically, you effectively grounded your amp via the patchbay, and probably all the rest of the gear connected to it.

Was this a transformer based DI box, or a unit that takes 48v or battery?

I'll let somebody more knowledgeable with tube gear take it from here, but man...you gotta have stuff grounded, particularly vacuum tube gear running at high voltages like that. Firstly for safety's sake, and you are lucky you are not injured or dead. Secondly, many pieces of gear in your studio rely on ground for noise rejection. If I have a rack unit that is using a wall wart, sometimes I will even ground it's chassis.

Old vintage amps and PA's were death traps with the two prong plugs. There are many stories (and a couple / few on here @ GS) about people being electrocuted, and either dying, or being in a coma for weeks with severe burns all over their body.

You are also very lucky it didn't take out all your gear downstream, ala your converters etc., and other things connected to your patchbay.

In short, you are lucky that ground on the other gear was secure.

Ground lifts = quick and dirty band aid, and basically are a bad way to go about eradicating noise.

Get that plug fixed immediately, if not your amplifier in general now.

Again, maybe a vacuum tube guru can chime in.

Be careful,
john

Thanks for the reply. I purchased the amp used recently, haven't gotten the ground plug fixed. Dumb, totally, I get it. I've been electrocuted from an ungrounded amp before. Sold on that one already.
Also, I mentioned twice, the amp was OFF for the entire time. I had absolutely no intention of running the amp without a speaker load. Never have, never will! Was simply plugging in the instrument cable to the DI and amp before I got to plugging in the cab and turning on the amp. Nothing out of the ordinary


Again, thank you for your response, and thank you for caring about my safety, that is definitely much appreciated.


Any electrical guys want to chime in about why the amp exploded while powered off? The DI is transformer based, passive. I have not replaced the fuse since, I will not run this amp until I fix the ground plug .
I should mention- everything was running off of the same isolated power line.

[NEWTON IN ORBIT]

Well, amp was off, but plugged in right?

Further, depending on how recently the amp was used, the caps can retain and hold a charge for quite a long time. These are some high voltage caps in there.
Could be 450 volts, not sure. There could be some fault, and you discharged a cap via your patchbay and it's ground buss.

Who knows, again, maybe somebody else will chime in. Regardless, if you are not an amp tech, and do not work on vacuum tube gear, I would get the amp looked at before using it again.

Anyway, at least you are breathing, hope nothing was damaged.
Happy 4th!

Good luck,
john

[joeq]

is it possible that the amp was plugged into a different circuit than the recording gear?

Old house? Sometimes, someone got his brother-in-law to add a line instead of a licensed electrician and something go reversed.

I was in a place like that, I got a lot of hums from situations whenever a guitar was connected to an amp on one circuit, and the console on the other. Amp alone, no problem, DI alone, no problem. But when grounded to both... I got hums, a shock or two, though I never blew up an amp.

A real electrician fixed it and never had a problem again.

[skills]

To avoid electrical problems, we had a licensed electrician set up the room, and he added an isolated line for recording gear. Nothing else in this room runs off of this line, and no recording gear is plugged into the non-isolated lines. But, now that you mention it, it is very possible that someone who didn't know this plugged the conditioner I was using for the amp into the non iso box, and I didn't check. This box goes to the same breaker, but may be a different circuit? I'm not sure how that works.

Also, the amp hadn't been used for about 2 weeks prior, so I don't think the caps had anything stored from then? Though, yes, it was plugged in...

Originally Posted by joeq

is it possible that the amp was plugged into a different circuit than the recording gear?

Old house? Sometimes, someone got his brother-in-law to add a line instead of a licensed electrician and something go reversed.

I was in a place like that, I got a lot of hums from situations whenever a guitar was connected to an amp on one circuit, and the console on the other. Amp alone, no problem, DI alone, no problem. But when grounded to both... I got hums, a shock or two, though I never blew up an amp.

A real electrician fixed it and never had a problem again.

[NEWTON IN ORBIT]

Originally Posted by joeq

is it possible that the amp was plugged into a different circuit than the recording gear?

Old house? Sometimes, someone got his brother-in-law to add a line instead of a licensed electrician and something go reversed.

I was in a place like that, I got a lot of hums from situations whenever a guitar was connected to an amp on one circuit, and the console on the other. Amp alone, no problem, DI alone, no problem. But when grounded to both... I got hums, a shock or two, though I never blew up an amp.

A real electrician fixed it and never had a problem again.

Yeah, this is spot on, but I think he said everything was through one iso transformer, guessing it was the same strip or outlet?

Yeah, though, the noise from two separate circuits is caused from time delay and phase issues with one circuit's 60hz hum (or 50 hz, depends where you are) and it's harmonics.

One will be later than the other, and the 60 cycle stuff will not line up, reinforcing, and cancelling at various points. Usually, never enough cancelling going on, always makes it noisier.

john

[never-enough]

Originally Posted by skills

Also, the amp hadn't been used for about 2 weeks prior, so I don't think the caps had anything stored from then? Though, yes, it was plugged in...

the caps can store their charge for MUCH LONGER than 2 weeks.

[skills]

Originally Posted by never-enough

the caps can store their charge for MUCH LONGER than 2 weeks.

Rad. How long do they store the charge?

[never-enough]

My understanding is that they store their charge until discharged, so even amps that have not been powered on in years can still be storing a lethal amount of voltage.