DISCLAIMER: USE AT YOUR OWN RISK. THERE ARE DEADLY VOLTAGES AND CURRENTS IN ANY TUBE AMPLIFIER AND YOU CAN KILL YOURSELF IF YOU DO NOT KNOW WHAT YOU ARE DOING. THE BELOW TIPS ARE FOR GENERAL REFERENCE ONLY.
1. SAFETY FIRST! Go read and study up on electronics safety. The GeoFX blurb on safety is a good start.You can kill yourself by doing amp work improperly!
2. Never put two hands inside an engergized circuit, EVER. One hand in the back pocket when taking voltage readings or chopsticking components.
3. Chopstick with a wooden chopstick, not a pencil. Graphite conducts!
4. Discharge the filter caps before working inside an amp. To do this, wire a 100K/1W resistor with insulated alligator clips on both ends (use some wire on one end of the resistor to give yourself some slack to work with). Be sure to shrink wrap any exposed resistor leads. Clip one end of the tool to the chassis, and then clip the other to the + side of the first filter cap. Use your meter to verify that no voltage remains on the cap before working on the amp. Make sure you remember to remove the discharge tool before powering the amp back up!
5. Learn to solder a proper joint BEFORE starting the amp wiring. Heat the turret and component (with a heat sink for capacitors and diodes) and flow the solder onto it. Don't "blob" it on.
6. Learn to read a schematic before starting your project. It's not hard, and if you start on an old Champ schematic, you'll learn all the basics right away.
7. Read the P1 Theory Document, even if you're not planning on building a P1. You won't understand everything, but it's a GREAT way to learn how amps work.
8. After you've wired your amp, go through a copy of the schematic connection by connection with a highlighter, making sure everything is there and properly connected. You will find at least one error, guaranteed!
9. Don't just turn the finished amp on. Get Paul Ruby's start-up guide and use it! Transformers are very easy to kill, and very expensive to replace. Be extremely careful on your first power-up. If you use Ruby's guide, 99% of the time, you will be golden.
10. To reduce filament hum, the center tap on the 6.3V secondary windings should be connected to the cathode of the power tube, not ground (this applies to cathode-biased power amps only). If your transformer doesn't have a center tap (if it only has two green wires, with no green/yellow striped wire), wire up two 100 ohm resistors to make a "poor man's center tap". Solder one end of each resistor to either green secondary lead, and solder the other sides of the resistors together. Then run a wire from where the resistors meet to the cathode pin of the power tube.
11. Plan your amp carefully, and use a paper template to mark your chassis for drilling. Use a center punch on all holes, and remember, you can always make a hole bigger, but never smaller...take your time.
12. This photo shows the proper way to wire an input jack. (Photo is from the fabulous Ampmaker.com kit build guide.)
13. When choosing a power transformer or output transformer. Pay close attention to the current handling capabilities, not just the voltages.
14. Use 600V teflon wire!
15. Never use 1/4 watt resistors in a guitar amp. 1/2 watt should be used in most signal paths, and 1 watt most everywhere else, unless the schematic specifically says otherwise.
16. When using shielded wire for signal leads, only ground one end of the shield, and shrink wrap the other end to make sure the metal braid doesn't short anything out.
17. Leave the "power" switch in the "on" position while working on an amp, and turn it off by unplugging it from the wall. This will keep you from accidentally forgetting that even with the switch in the "off" position, you have 115VAC on the terminals of the switch and, in some cases, fuse housing.
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