Dangerous Vintage Amps

[stratik]

Hello, There:

Great site - I get no work done when I visit here!

I 'fell-out' with music for many years during the keyboard/synthy/techy '80s, but I'm now delighted to be playing 'real' music once more - so I got the bug again and I want optimum sounds from a fine old guitar..

I just finished lining my old '69 Strat with copper and now I'm ready for the next step(s). I bought myself a 0.1uf 500V cap to solder onto the bridge wire going to the cavity. As far as I'm aware, this is to protect against the dangers posed by some vintage amps.
I just wondered, can anyone tell me who these vintage amps are? I don't think I'll ever encounter such a beast at my pub gig but I'd still like to 'know my enemy' so to speak. For example, we tend to like 'retro' stuff and would probably jump at the chance to have Jimi's tone - why not? - would we be ill-advised to plug into something he used in his heyday?

How old would 'vintage' be? Would this be pre '60's or much more recent? Would it be an old 'Vortexion' type amp or even some early Vox AC30 or Fender? Is it likely to be a US design - and therefore not a danger to us here in the UK? Would it be instantly recognisable as being ugly, old and have a metal chassis with big bakelite knobs, or is it a 'benign' but insidious monster? Would it be a combo or an old amp head? Is the inherent fault something that would be immediately obvious to the layperson if 'we' were told what to look out for when in doubt? Does it/they have a name? Do guitarists still use them???

If I were to meet someone who owned Charlie Christian's' original 'super-duper' amp, stated that it was the beez-neez and invited me to plug in, I'm sure I'd be very tempted to crank my old Strat through it... just to hear what it was like - should it be avoided like the plague as it would most certainly carry this particular deadly 'fault'?
My first good amp was bought in the late 1970's - it was an 'Orange' 80 watt combo and I wish I still had it; a great amp, I'd buy it again - would that amp be considered 'vintage' and, perhaps, dangerous?

The point I'm getting to is that I would like to 'tart-up' my old Strat with some nice metal knobs (why not?...)* but am aware of the fact that these are not safe when confronted with the vintage amp problem (nor is the jack socket and, perhaps, screwheads, for that matter).
So, it means if I buy the metal knobs then the 0.1uf 500V cap is rendered almost pointless (although, it would still be pointless if I were to pull my gtr cable out and unavoidably touch the jack socket)

Apart from the dangers from bad house wiring at gigs and any lack of personal 'due diligence', I'd appreciate a name or names of any amp that posed any such danger. I would then pimp my old Strat with the tarty knobs!


*Some would consider it a minor crime to change the appearance of their old guitar - I was in London recently and the gtr. tech 'Andy' was delighted that I was actually 'gigging' my old Strat - he made the point, "It's really nice that your old guitar is being used"... implying that vintage guitars are bought as 'trophys' and not for the purpose they were intended. Dear me.

Thanks for any help here.

[dd842]

Hi stratik,

I'm going to save you the confusion of me even trying to answer that, BUT ...

For taking such time and detail to your first post, I do feel it deserves a big WELCOME! to GN2!

Great first post - and I am also eager to hear the answer!

Dan

[wolf]

Stratik
I believe tube amps are more dangerous than solid state because the tube (or valve as the Brits say) amps require considerably more energy to power those tubes. (I'm sure someone more knowledgeable will be along to explain it better.)

I'd say that generally speaking, old amps (tube or solid state) were never designed with safety in mind. I go back to the 1960's and amps didn't even have "grounding" plugs then. You got too much hum? Turn the plug around. ;D I don't know how many times I got zapped way back when by playing a guitar that had a huge potential difference with the microphone. Also way back when, picking up 2 "live" guitars at the same time literally could have been fatal.

Which brings me to a question for you. You are concerned about metal knobs on a guitar. You do realize that all the strings are "grounded" (or "earthed") to the guitar circuit and all the way back to the amp? That's why people get electric shocks (or even electrocuted) while playing the guitar.

And welcome to Guitar Nuts 2 !!!

[sumgai]

stratik,

And I too welcome you to the Nutzhouse! ;D

The problem to which you refer is actually very limited in scope, but not in terms of which amp might be more susceptible to shocking you. The term 'vintage' is misleading, except that age does play a part in deteriorating components. The problem can happen even in a brand new amp that used sub-standard parts.

In brief, the capacitor you installed gives you a measure of relief from the possiblity of the ground become a very high potential for a short period of time. This will happen only when the rectifier circuit of a tube amp blows its mind, and puts the B+ (greater than a couple hundred volts) onto the ground line. Yes, this is a short circuit, and it will blow the fuse........ the only question is, when will said fuse blow?

Not until after you've been "notified" that the amp has a problem. And at that, this is all predicated on the fact that you: a) must be standing a puddle of water (or in a wet basement); b) must be touching some other piece of electrical gear, such as a microphone; and/or c) must be too drunk to have taken the usual safety precautions.

If you're really paranoid (defined as being a ChrisK wannabe when it comes to safety), you'll have someone else test all the possible connection paths before you 'mount up' and start playing. But even then, the fault only occurs for about 1/60 of a second (a tad longer in Europe), and then it's all done. Using a patsy some other dude for this particular problem can't be done, sorry to say.

The capacitor will only reduce the amount of current carried to and through your body, it won't eliminate it entirely. But that reduction will likely mean that you survive to tell your grandkids of the day you nearly bought the farm, down at the ol' grandstands. Slightly better protection might be afforded with a 0.33µf cap, but if you're not inclined to monkey around any further, that's understandable, what you've got should do the trick.

HTH


sumgai

[stratik]

Thanks for warm welcome and answers, guys. ;D

I think most of the players back here in the UK have experienced the zap on the lips from the mic when about to sing - it's not nice However, we soldier on and tend 'not to talk about these things too much'.. Thankfully, instrument manufacturers, venue management and Health & Safety (UK) requirements have made 'dodgy' gigs less of a problem - but we still shouldn't ever become complacent.

We had a very unfortunate incident in the '60s when accomplished guitarist Les Harvey (Stone The Crows) was fatally injured onstage. I worked as a salesman in a music store during that time and the amount of 'Playsafe' devices sold went through the roof. The Playsafe was a fused (I think) cylindrical device with a jack plug in one end and a female jack socket on the other. It plugged into your guitar and your gtr. cable plugged into the female end, the idea being, if their was a 'problem' your guitar would suddenly stop playing and you would live to see another day. I'd buy the modern day equivalent if I knew where.

...I'm still gonna get those tarty knobs.

Thanks.

[sumgai]

stratik,

As it happens, Lee is the only recorded case of a death by electocution while on-stage during a performance. But for purposes of safety, IMHO the rumor mill is justified in distorting the truth all out of proportion. This time anyway.

A few other performers have been "sent down to the farm" (Who can tell me where that euphemism came from? ), but no others were during a real live, honest-to-goodness gig. Rehearsals (where thoughts of safety should be highest, but are more likely at their lowest), in homes, even in a bus, once. There's a web page on it somewhere, and I know I quoted from it in an earlier thread on this Forum, but I'll be bleeped if I can find it now............


sumgai

[ashcatlt]

I find it interesting to note that sumgai didn't play that whole "I'll let some of the newer guys flex their muscles" shtick on this thread. This is important stuff and misinformation - even well intentioned - could lead to dire consequences.

[guitardoode]

i quite agree ashcatlt.
Although i do think in this new days of technology and blah.
If there were some sort of short, the grounding on the amp should resolve it. And im not too sure but i think there could be RCD circuits that will cut out the amp if there is some sort of short... Either in the amp or on the mains.
To be honest im only guessing at that.
My house is rigged with RCD units so if theres the ground gets a potential difference the mains shut off, i mean ive got a relatively new Marshall Solid state. Its got a metal front plate, like most amps do. and im sure the jacklead to the guitar is grounded onto that.. so i was sorta guessing couldnt if the amp even go live. Instead of traveling into me via guitar. just go down the amp's ground, picked up by the RCD, Power cuts out. No more live amp?

To be honest i feel like im just bantering here... maybe someone could expand or turn my words into something of sense? ;D ;D

[sumgai]

guitardoode, you need to pay closer attention to ashcatlt in order to learn how to post while impaired. ;D

But you made sense enough, or you did until I came up against "RCD". Doode, what the heck is that? If your description is correct, around these parts that device is known as a Ground Fault Interrupt (or Ground Fault Current Interrupt). GFI (GFCI) for short.

And yes, manufacturers of any equipment that might be used outdoors should be required by law to build these things in right at the factory. Failing that, you can do the same thing by making your own power strip with a GFCI outlet, available from nearly any home center or hardware store - they're about 10 bucks (Merkin). You might even be able to slip one inside of an already built power strip, who knows?

Hint: If you're builiding your own home, ask the electrical contractor to install a whole-house GFCI unit at the breaker box. You won't be sorry.

HTH


sumgai

p.s. ash, right you are. Tone is the reason we're all here, but if we're not safe, we won't be here to enjoy the tone. (Damn, I"m beginning to sound like you! ;D)

[UnklMickey]

sumgai said:

Hint: If you're builiding your own home, ask the electrical contractor to install a whole-house GFCI unit at the breaker box.

Whole house? That seems like a really bad idea to me. That would mean that the mains would go open for the entire house for a fault in any circuit. I can't speak for anyone else, but I for one don't want to be in a dark house in the middle of the night unnecessarily.

GFCI breakers on every individual circuit, sounds like a much better idea to me. That way a zone would go dead, rather than the whole house. If a contractor is really thinking, the lighting and outlets would be on separate circuits, as well. That way, a fault on an outlet circuit, would not cause the lights to go out, even in the room where the fault occurred.

[sumgai]

unk,

I spoke in a general term, whole house meaning that everything is treated right at the breaker box, but you're correct, it can be done only with individual circuit breakers. In fact, the early forms of these used two slots per circuit, but they've managed to slim them back down to one slot per device by running an external pigtail to the buss bar. (I've seen 'em as high as 60 amps!)

For some reason, electrical system designers and architects like to conserve wire. They think that if you run 60 ft of 12-2w/g to a room, you might as well do the whole room, lights and outlets, there's no reason to run a second 60 ft of line. And the installing sub-contractor won't have to spend all that "extra" time on the second run, yielding even more savings.

Sometimes they're right to think of the wallet, but it sure does cause a lotta grief after the fact for people like you and me who mess around with things electrical, and suffer "lights out" when we get underly cautious and trip the circuit breaker.


sumgai

[guitardoode]

sumgai said:

But you made sense enough, or you did until I came up against "RCD". Doode, what the heck is that? If your description is correct, around these parts that device is known as a Ground Fault Interrupt (or Ground Fault Current Interrupt). GFI (GFCI) for short.

Sorry Sumgai! RCD is probably the Brit term for it. It does detect a fault in the ground.
Im not sure how houses are wired up in the US but down here the older houses/Majority are on ring circuits. and by law they all need a GFCI? on each ring.
The goverment want to universalise to the European format for new houses. with a star network. and a fuse in the each individual socket. I dont know why...
But we also have seperate ring circuits for lights.

Posted by sumgai on Yesterday at 3:50am
unk,

For some reason, electrical system designers and architects like to conserve wire. They think that if you run 60 ft of 12-2w/g to a room, you might as well do the whole room, lights and outlets, there's no reason to run a second 60 ft of line. And the installing sub-contractor won't have to spend all that "extra" time on the second run, yielding even more savings.

We have that problem down here. Most of our Electricians are really useless all self employed and do riddiculose things. and major bodged work. purely because they get it done quicker.

[sumgai]

GD,

So where's "down here"?

And I stumbled, purely by accident mind you, across the defintion of RCD..... it's "residual current device". To my mind, that's really stretching the defintion of residual, but so long as the principle is understood, and applied properly, all is well, right?

When you are a little boy, and you dream of becoming an astronaut, the best thing an adult can do is to remind you that will be sitting on top of a multi-ton rocket built by the cheapest bidder! That may shatter your dream, but you'll live longer to pass that dream on to your own kids. ;D The same thing applies to those who monkey around in the wiring of their homes - it was done by the guy who bid the cheapest job. 'Nuff said.


sumgai

[gumbo]

Hmm..
..late post, dead computer...grrr!

FWIW Sumgai, RCD is the terminology used in Oz, which is also "down here"....:-)
...and I've always thought it was a mis-nomer too...

We also have a proliferation of what is generally known (at least at the electrical department of the big hardware chains) as a 'safety switch'....that terminology at times worries me, 'coz I can just picture the situations that some idiots place themselves in, thinking that the device will save them.....(!!)

..although, that said, I DO travel with one of the portable in-line versions in my bag of "gig goodies" for insertion in the power citcuit supplying my Bassman 59RI...maybe I'm just kidding myself like those other guys.....

So far, my ears don't light up when I hit the strings..

[sumgai]

gumbo,

So far, my ears don't light up when I hit the strings..

They don't? Then perhaps it's time to change the bulbs in them, don'tcha think? ;D


sumgai

[Ripper]

I remember Ace Frehley getting zapped in the 80's.
He was walking down the stairs that were a part of the stage design, touched the railing with his hand and caused some type of ground out. He was helped offstage, came back later but after the gig said he couldnt feel his fingers for the rest of the concert.

After that KISS went all wireless.

I too have a wireless unit for my guitar. I bought it years ago, and it still does a great job.
I believe its a Samson wireless.

[sumgai]

deep,

If someone made a wireless unit for my 13-pin setup, I'd be all over it like stink on ......!

Even so, much of Roland's gear is relatively safer than most rigs. They use an isolation transformer, aka a wall-wart, to power their GR series of guitar synths. You know it's truly isolated when there are only two prongs on the 110v/220v side of that wart. Which is the case with about 99.9% of all wall-wart (or middle-of-the-cable transformer) designs.

But I digress............. Yes, a wireless system has too many advantages, except in one important area - cost.


sumgai

[gumbo]

When you find that 13-pin wireless unit, buy two, and I'll appear on your doorstep instantly...(with lighted ears)...

[sumgai]

gummy,

When you find that 13-pin wireless unit, buy two, and I'll appear on your doorstep instantly...(with lighted ears)...

Yeah, that'll be a licence to print money! ;D


sumgai

[slideking54]

nec requires ground fault on all main breakers 1200a. and above. last i knew. would be expensive to put it on the main in your house. you also have to remember these things are not designed to be continously tripped. one hard fault blows them up. it is your resistance to ground that determines the current that will flow through you . i wont recommend to any one to play barefoot on concrete. i dont like them, but go wireless. oh and the sensitivity varies,that is some of the price difference on the receptacle. there are osha approved cords for power tools with these built in . hope this helps.