It is currently Mon Mar 16, 2020 10:49 am

All times are UTC - 7 hours



Post new topic Reply to topic  [ 13 posts ] 
Author Message
Post subject: Life saving info on high voltages in tube amps. Please?
Posted: Mon Dec 29, 2008 3:08 pm
Offline
Hobbyist
Hobbyist
User avatar

Joined: Thu Dec 25, 2008 5:22 pm
Posts: 19
All of us that have tube amps are aware of the high voltages stored in some of the components. I was hoping that someone here may be able to tell us which components are dangerous, and how to spot them, as it is sometimes necessary to open cabinets for different reasons.

I've heard of at least one method of "bleeding off" these voltages before opening the cab, but don't want to post that info here, in fear that it is incorrect. Don't want anyone getting hurt.

So, is anyone here familiar enough with these components to offer any advice?


Top
Profile
Fender Play Winter Sale 2020
Post subject:
Posted: Tue Dec 30, 2008 10:19 am
Offline
Hobbyist
Hobbyist

Joined: Wed Jul 30, 2008 5:42 pm
Posts: 26
Ooh, this is dangerous. I KNOW the capacitors (those cylindrical things) can hold LOTS of voltage...I'm thinking 300 - 400 Volts? and there are probably other components that store voltage in there, too.
Find a neighborhood electronics shop or music store to do it for you. I befriended a retired Air Force guy who builds all kind of crap to teach me. The Guitar Amp Handbook by Dave Hunter is a great read for us amp geeks. Be careful...but have fun!


Top
Profile
Post subject:
Posted: Tue Dec 30, 2008 4:55 pm
Offline
Professional Musician
Professional Musician
User avatar

Joined: Mon Jul 16, 2007 5:33 pm
Posts: 1084
Location: NoHo in SoCal
The caps can (and do!!!!) store a fatal charge, possibly for days or longer after the amp was last plugged in. I don't have pictures handy but you'd see them in amp repair books.

Keep in mind that you need to be careful more than just right around the caps themselves. They're connected to other circuits and there can be significant danger in touching the metal frame and any other component. For instance, a cap on one side could discharge "through" a transformer (to ground) on the other side of the chassis.

You can discharge them but should use only a screwdriver with a well insulated handle. You carefully short the positive (+) side of each to the metal chassis. You should be on a dry floor and wearing shoes with rubber soles and keep your other hand in your pocket when you do that.

I'd also suggest safety goggles in that you can get a pretty nasty spark when you do the discharge. There's also a small chance that a going bad cap will explode on you.

However, you should be able to change the tubes in most of the amps I've ever seen without removing the chassis from the case. Use a cloth or something else soft and work the tubes out carefully. As above, one hand in pocket is the best idea. That way, you're not touching the tube with one hand and something you shouldn't with the other.


Top
Profile
Post subject:
Posted: Tue Dec 30, 2008 5:21 pm
Offline
Hobbyist
Hobbyist

Joined: Wed Jul 30, 2008 5:42 pm
Posts: 26
I actually made (with help from my old mentor) a wire with clips on the ends and a resistor in the middle to control and slow the drain.It waspretty interesting to watch it drain wth a multi-tester. Oh, yeah, do it more than once; I watched them charge back up after we removed the wire. Everything HAS to be capable of handling high voltage, though. I'm a serious geek and I was nervous at first. (You keep one hand in your pocket so voltage can't travel from hand-to-hand and hence, through your heart!!!) Be careful!


Top
Profile
Post subject:
Posted: Tue Dec 30, 2008 6:41 pm
Offline
Amateur
Amateur
User avatar

Joined: Sun Aug 12, 2007 4:59 pm
Posts: 183
Location: Fort Myers, Florida swamp
Check out DVD's by Gerald Weber of Kendrick Amplifiers (he has books also) on Amp Repair...
All Experience levels can benefit from this guy! And, he is a big Vintage Fender Amp Fan!
I won't give advice for fear of hurting someone in this forum...
So, do not connect a jumper wire to the back of pin #1 of the pre-amp tube closest to the input socket and run it to ground---WITH THE AMP UNPLUGGED... (which slowly discharges the amp.)
P.S. it's not voltage that Kills you. Voltage is the the measure of power applied... Amps or amperage is what kills you which is the measure of current flowing through the circuit (or your body.)
And Direct Current (DC) kills you really dead, which is what flows out of those capacitors at high amperages after being stored up... even with the power off... Good luck!

_________________
I love the smell of hot vacuum tubes in the morning...


Top
Profile
Post subject:
Posted: Wed Dec 31, 2008 9:28 am
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
The best thing to do if you really need to poke around is to keep one hand in your pocket. allanf64 is correct on all counts.

allanf64, just a quick off topic question, are you a photographer?
I am and the f64 caught my eye.


Top
Profile
Post subject:
Posted: Wed Dec 31, 2008 2:20 pm
Offline
Amateur
Amateur
User avatar

Joined: Sun Aug 12, 2007 4:59 pm
Posts: 183
Location: Fort Myers, Florida swamp
63supro wrote:
The best thing to do if you really need to poke around is to keep one hand in your pocket. allanf64 is correct on all counts.

allanf64, just a quick off topic question, are you a photographer?
I am and the f64 caught my eye.

I am a Sales Supervisor for a Budweiser wholesaler...(a Beerman! or "Budman"). For the last twenty years... and a Guitar player / collector on the side and a part time Bouncer / janitor for my family owned Honky Tonk bar ...
But, my very first job out of High School was an "Aviation Electrician" Petty Officer 2nd Class in the U.S. Navy!
And I still love fixing my own Tube Amps on the side as a result of my training... WE actually worked on old planes that still had tubes in them back in the early 80's! Thanks for asking!

_________________
I love the smell of hot vacuum tubes in the morning...


Top
Profile
Post subject:
Posted: Thu Jan 01, 2009 12:51 pm
Offline
Rock Star
Rock Star
User avatar

Joined: Tue Aug 07, 2007 2:19 pm
Posts: 8827
allanf64,
Very cool. I love Bud. I was worried about the takeover, but I just bought a case of American Ale for New Years and it's excellent.

I was brought up on tube amps. I've been playing close to 42 years.


Top
Profile
Post subject:
Posted: Thu Jan 01, 2009 8:00 pm
Offline
Amateur
Amateur
User avatar

Joined: Sun Aug 12, 2007 4:59 pm
Posts: 183
Location: Fort Myers, Florida swamp
supro63,
The buy out by InBev really has not changed much... Anhueser Busch beers wil still be brewed in the U.S.A... If you like the new ale try any beers brewed by KONA out of Hawaii. (the pale ale is delicious)
By the way, I love the Member name Supro63! I have never played through an old Supro, but would like to.
My first amp ever was actually a Solid State Kustom 1 Lead (12" speaker 30 watts and loud as hell).
My first "tube amp" was a 1966 Fender Pro Reverb which I still have, I bought it for $300 and would not sell it for $3k now - I love that amp.I probably DO need to sell off some stuff though,( not my Fender stuff!) Last count -13 amps -
I am 44 yrs. old... And I've been whackin' away on my guitar since I was 15...

_________________
I love the smell of hot vacuum tubes in the morning...


Top
Profile
Post subject:
Posted: Thu Jan 01, 2009 8:08 pm
Offline
Amateur
Amateur
User avatar

Joined: Sun Aug 12, 2007 4:59 pm
Posts: 183
Location: Fort Myers, Florida swamp
By the way... back on topic. If you DO want to open up your amp and check for burned components, loose wires etc. Use a wooden chopstick! Wood doesn't conduct electricity - you can poke around and find loose solder joints, broken wires etc. and then eat some egg foo young.

and drink some SAke...

I love SAke!

_________________
I love the smell of hot vacuum tubes in the morning...


Top
Profile
Post subject:
Posted: Sat Jan 03, 2009 2:28 pm
Offline
Amateur
Amateur
User avatar

Joined: Mon Nov 19, 2007 9:47 am
Posts: 116
---


Last edited by tinker tech on Wed Jul 29, 2009 10:34 am, edited 1 time in total.

Top
Profile
Post subject:
Posted: Sat Jan 03, 2009 3:03 pm
Offline
Amateur
Amateur
User avatar

Joined: Sun Aug 12, 2007 4:59 pm
Posts: 183
Location: Fort Myers, Florida swamp
I fully agree with you Tinker Tech...

_________________
I love the smell of hot vacuum tubes in the morning...


Top
Profile
Post subject:
Posted: Sun Jan 04, 2009 7:11 pm
Offline
Aspiring Musician
Aspiring Musician
User avatar

Joined: Mon Sep 01, 2008 10:04 am
Posts: 508
Location: Ohio
+1 with what Tinker Tech and Allen said.

As we used to say in the Navy: "If you don't know what it is...Don't F**k with it!!!"

-Harley 8)

_________________
I only have two brain cells left, and I'm saving them....for this weekend!


Top
Profile
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 13 posts ] 

All times are UTC - 7 hours

Fender Play Winter Sale 2020

Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to: