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Post by benttop (Steve) on Jul 23, 2014 17:08:25 GMT -7
If you decide to poke around inside your amp, this could be the most important ten minutes of the rest of your life.
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Post by heynewguy (Ol’ Bill) on Jul 23, 2014 18:06:47 GMT -7
I just watched that today. Very well done. A must for anyone with a tube amp.. Thanks for posting Steve.
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Post by BritInvasion on Jul 23, 2014 18:21:30 GMT -7
Vital to know this stuff , great post Steve!
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Post by muZician on Jul 23, 2014 22:10:22 GMT -7
thanks for posting. very useful!
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Post by simpleton on Jul 23, 2014 23:38:31 GMT -7
I've been wondering that very thing for some time now .... Now I know what filter capacitors are and not to go grabbing them. Killer info.....technically none killer info i should say.
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Post by doctorice on Jul 26, 2014 9:02:10 GMT -7
Nicely done tutorial.
I'm glad he made it clear near the end that you (1) unplug; (2) check fuse and then (3) discharge filter caps in that order. I wasn't sure the discharge to ground was done with the AC cord plugged in or not.
I'd like to see him review safety when biasing an amp, since that has to be done under power.
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Post by strat59 on Jul 26, 2014 10:39:21 GMT -7
Shocking information Steve. LOL Seriously, very good info for all to know. I wish someone had informed me before I touched a filter cap in an unplugged 100w Marshall at age 15. I didn't really ever pay attention to the watch pocket in my jeans before that. Saw stars & knocked my ---- in my watch pocket. Found out troubleshooting without proper knowledge leads to trouble. Thanks for posting.
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Post by Paul (TRANE) on Jul 26, 2014 11:09:15 GMT -7
I used to design pad mounted switch gear. 60,000volts at 1,200 amps. Now that was a scary thing to be around during testing. Of course it only takes around 1mA to or so to kill a man. Some really serious voltage and current in a tube amp. Great tutorial. Safety first.
Sent from my SM-N900V using proboards
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Post by benttop (Steve) on Jul 26, 2014 19:27:57 GMT -7
I got hit working on an Ampeg amp once - 750VDC right off the SS Recto. But I had my left hand in my back pocket, so I just flew back a ways and was pretty shook up. It is difficult learning respect the hard way. That inadvertent touch would likely have killed me if my other hand had been on the chassis.
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Post by zpilot on Jul 27, 2014 11:16:02 GMT -7
I got hit working on an Ampeg amp once - 750VDC right off the SS Recto. But I had my left hand in my back pocket, so I just flew back a ways and was pretty shook up. It is difficult learning respect the hard way. That inadvertent touch would likely have killed me if my other hand had been on the chassis. I had a similar experience one time after I had been working on amps long enough to think I was pretty sharp and started to get complacent about safety. I think I've related the story before on the forum. It only takes once to learn your lesson.
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Post by Harvey on Jul 27, 2014 12:03:52 GMT -7
Cool info Steve, so now I can touch this thingie right here BZZZZZZZZZZZZZZZZZ............................................jus kiddin'
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Post by gplayer1965 on Jul 28, 2014 15:26:27 GMT -7
I am scared...in a good way
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Post by Brimstone on Jul 28, 2014 17:33:27 GMT -7
My first amp was a 1959 Ampeg Jet. I wish I still had that one. It had a bad ground someplace. Had to turn it on and off with a pair of pliers to keep from getting zapped. I still miss it.
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Post by kiki90291 on Oct 25, 2014 10:53:05 GMT -7
Two follow up questions - if the amp isn't plugged in, how does the chassis go to ground?
I have a Prescription JR that has two big blue caps on the bottom of the chassis - it's not clear to me how you get to th positive lead on those to discharge them?
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Post by zpilot on Oct 27, 2014 18:31:57 GMT -7
Two follow up questions - if the amp isn't plugged in, how does the chassis go to ground? I have a Prescription JR that has two big blue caps on the bottom of the chassis - it's not clear to me how you get to th positive lead on those to discharge them? The chassis IS ground. In other words it is at zero volts potential in relation to the positive leads or terminals of the filter caps. The terminals of the blue caps are inside the amp chassis and should be labeled '+'.
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