Wednesday, January 11, 2017

Hell Yeah, I'm Building An Amp!! Part 2

Well, the kit arrived, and everything looks great! I decided to use a holiday gift card to upgrade my soldering iron to the industry-standard Weller WES51; cheaper irons are fine for little things like pedals and guitar pickups, but i'm not taking any chances with amplifier connections. I'd prefer any mistakes be limited to my lack of experience and dingus-like tendencies, rather than cheapskate tools.

Step one, make sure everything you need is actually in the package, particularly the small components. I measured each resistor with my Multimeter, checked them off on the parts list, and began dry-mounting them on the eyelet board, followed by the smaller capacitors, and lastly the large electrolytic caps.

In any type of circuit, always note the orientation of the electrolytic capacitors on the schematic and/or wiring diagram, indicated by a + on one end, as they dictate the direction of voltage flow and won't work if wired the wrong way (or maybe explode in your face like a jack-in-the-box if you're really lucky). Also, there are a few components that attach directly to jacks, pots, or switches... be sure to keep them in a safe place for later.

I missed the fine print and didn't realize that this kit does not include any mounting hardware for the chassis... kind of a drag, but nothing a trip to the hardware store can't fix once I'm at that point. Hopefully there's a list somewhere on the internets of nut and bolt sizes for this, and I'll include them in this blog when discovered.

Loaded eyelet board, no solder yet. 

After double- and triple-checking that everything is mounted properly, it's time to heat up the soldering iron, and I was immediately happy that I upgraded. After years of using crap Radio Shack irons, the switch to an industry standard like Weller is HUGE... big league, even. The variable temperature control is incredibly useful, plus it heats up super fast, just a few seconds. Soldering was a breeze with this guy.

No, Weller doesn't pay me to say this, but they should.

Soldered eyelet board

Rear of eyelet board, note connection of electrolytic caps on lower left

Next, I began prepping some of the chassis-mounted components, like the 68k resistor on the input jack, and the 500pF capacitor that connects the volume and tone pots. In order to get the lengths right, you've got to place them in the chassis and line them up with the eyelet board, rather than estimate and potentially waste wire. 

Some chassis-mounted component connections

Shiny chrome faceplate, with one of the input jacks modified into a 3-way boost switch (one of the reasons I chose this kit).

Update 1/12/17: Continued with wiring up some chassis components like the pilot lamp, power switch, and fuse holder, and also prepped the leads from the Power and Output transformers, which mount underneath the chassis. I'm a little nervous that these leads might be too short, but won't know for certain until I mount the tube sockets, which requires a trip to the hardware store (my only gripe about this kit, lacking about $.80 worth of nuts and bolts that would make life a lot easier).

Update 1/15/17: Just about finished wiring! Mounted the tube sockets Friday morning after running to Lowe's for machine screws and nuts, then got to the wiring this afternoon, along with the power and output transformers and all internal connections.

Tube sockets, exterior & interior.

Getting the sockets wired to the board

The entire chassis, with transformers mounted & wired.

Closeups of each end

Using my multimeter, I checked for continuity in all connections, including the grounding scheme; it's fun to hear the little "beep" when you've got a solid connection. All that's left is to wire up the AC cord and flick the power switch, which I'm still deathly afraid to do. Fortunately, I know a great amp tech, Jamie Simpson of BOOYA! Amplifier Services in Lake Hopatcong, NJ, and I'll be taking this project to him for a final inspection before any voltage is applied. I'm sure it'll be a great lesson from a pro, and hopefully I'll pick up a few tips for the future and the final installment of this series. In the meantime, I should probably clean up my workshop...

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