My AX84 Experience:

The Build:

When I got ready to order parts to build my AX84, I was torn between the added features of the standard Rev 9 schematic and the simplicity of the Rev 9 'lite' schematic.  I elected to use most of the Rev 9 as listed, but used the optional solid state rectifier, the standby switch and none of the other switches (for gain, triode/pentode, etc...).  I used the Hammond 269EX transformer for power and the 125E universal output transformer (rated up to 15 watts.)  My speaker was initially a radio shack 8 ohm woofer in a custom cabinet, but I later used my Ampeg 412 cabinet with celestions.

Per Nuke's suggestion, I used a 9x14 uncoated cakepan as a chassis, figuring that I might have punching problems or some such that would require me to start over from scratch, and the $3 price tag was appealing.  

The only tools I purchased was a "unibit" from Home Depot for $34.00, which drills holes nicely in the pan.  It generally leaves one side sort of ragged, but turning the bit around and drilling from the other side cleans this up quite a bit.  The unibit is real good about staying in the spot where you're trying to drill.  It bites down real well.

I elected to use a piece of 1/2" plywood and a number of small zinc screws for the purporse of mounting my components.  After working with a layout on paper until I got one that was as neat as possible, I placed the screws in the wood at locations that would serve as solder points for resistors and such.  Each screw head was sanded, then tinned with a 100w soldering gun.  I now had a bunch of solder points with solder already in place so that my small 30W iron would melt the solder and not have to heat the whole screw (a feat which it would not happily accomplish.)

Assembly took several sittings.   Given a few hours straight, I could have assembled everything in one sitting, but it would have been tedious.

The Errors:

I initially made a wiring error that had the filament lines on the power transformer shorted together.  Needless to say, the transformer was not happy about this, and since I didn't notice for several minutes, the transformer cooked.  

I built a "short-light" following directions on the internet to help protect against a dead short in my circuit.  Short Light consists of a high wattage light bulb and socket wired in series to the hot-line of the main AC power.  I accomplished this by cutting a power cable open, cutting the hot wire, attaching one terminal to one side of the lamp, and the other wire, to the other terminal.  This normally does nothing, but if the neutral line should somehow become shorted with the hot line, the light bulb will light up and burn indicating a short.  I don't know that the bulb provides any protection other than "if you see it light, turn it off quickly"

After correcting this fault and replacing the transformer, I moved from "smoke and smell" to "everything looks OK, but no sound".

I reviewed my circuit a few times and determined that (a) I never finished hooking up the power to my output transformer and (b) the secondary was again shorted.  A wiring error to my impedance switch selected which tap (5 or 6) to short with the common tap (2).  Since both 8 and 4 ohm taps used one of the same wires, I just used a switch to choose between the remaining taps.  I was luckier with my output transformer short than with the power transformer short:  When I corrected these problems, I got sound.  

Horrible buzzing, actually.  I went through the circuit trying to determine what the cause might be.  Removing the preamp tube did not stop the buzz, while removing the power-tube did, so I figured the problem was somewhere after the preamp circuit, but the power-tube was at least involved.  Turns out that I forgot to connect the negative legs of my filter capacitors to ground.  I corrected this and turned on the unit.  It buzzed a little, but the horrible buzz was gone.  Touching a guitar cable to my finger produced the familiar clicks of a working amp.  Plugged in a guitar and it worked.

A valuable lesson:  before you power up, double and triple check not only the physical wiring of your unit, but also make sure that your wiring diagram matches your schematic.  If you can have someone else look over your wiring, this will be a big help too.  I found both of my problems trying to explain how the device worked to someone else.

First Experiences:

Keep in mind that my first experiences used a radio shack speaker which is a bit raspier than a normal guitar speaker, but it was expendible.

I noticed that I wired all of my pots backwards, so rather than turning them clockwise like most devices, you have to turn them counter-clockwise like a water faucet.  I thought it was funny to say you had to "open the valve and let some sound out"

Other:

I performed the modifications recommended by Eric Barbour, and a minor touch up by Randall to allow use of an SV83 tube in place of the EL84.  I can switch between the two now, turning it off first, of course.