# electronics novice needs safety tips.



## Cary (May 11, 2011)

As the title says, I'm a complete novice when it comes to electronics, but I want to start tinkering a bit, with the goal of being able to so my own tech work (biasing, modding etc.) and eventually putting together a kit from weber or mojo or the like.

I have a soldering iron that gets a lot of use on my guitars, a multimeter (if my friend who borrowed it ever returns it) and a couple other basic tools. 

I guess my first question is about discharging my amp of any current. I've done a couple minor repairs (replaced reverb output phono jack and fuse holder) but i've done them in total fear of zapping myself. Is it enough to just power off my amp (ab 763 super reverb clone) and continue to play until the sound fades, or are there further measures I have to take? I want to do a few more things and I'd way more comfortable if someone could tell me how to not kill myself.

Next question is how do I measure and adjust the bias of my amp? This is something i'd like to be able to do myself, techs want so much money for this, and if want to experiment with a bunch of tubes it will cost me a fortune.


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## notjoeaverage (Oct 6, 2008)

This should get you started
http://www.ax84.com/safety.html


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## loudtubeamps (Feb 2, 2012)

Manuals that are specific to tube amps and repairs are a must.
The Tube Amp Handbook: Aspen Pittman
A Desktop Reference of Hip Vintage Guitar Amps:Gerald Weber
These books are great for reference (good schematics, date codes etc.) as well as tips, mods and should guide you through most amp projects.
Cheers, Doug


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## keeperofthegood (Apr 30, 2008)

A long time fav site online is http://www.repairfaq.org and this page is full of useful information on safety http://www.repairfaq.org/sam/safety.htm Being almost void of images (almost pure text) it is a very bandwidth friendly and fast site. Lots to read there


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## keeperofthegood (Apr 30, 2008)

And to answer about the caps: http://www.repairfaq.org/sam/captest.htm



> For the main capacitors in a switching power supply, TV, or monitor, which might be 400 uF at 350 V, a 2 K ohm 25 W resistor would be suitable. RC=.8 second. 5RC=4 seconds. A lower wattage resistor (compared to that calculated from V^^2 / R) can be used since the total energy stored in the capacitor is not that great.


That gives you for a 400uF cap 4 seconds to discharge it (not fully, but after 5 time constants you get into calculus to determine how long till all charge is gone).

To understand time constants as used here http://www.utc.edu/Faculty/Tatiana-Allen/rctime.html


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## mhammer (Nov 30, 2007)

Two longstanding safety tips for those working on tube amps are to:

a) always work with one hand in your pocket

b) always have a wooden or plastic chopstick to poke at things


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## Cary (May 11, 2011)

looks like i've got some reading to do. Thanks for all the responses folks.


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