GuitarMasterClass Blog

I had some time this weekend and have started making a few minor modifications now that the basic amp is working, I also worked on some cosmetic touches.

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My previous words were prophetic - as it happened I got both sound and fizzing noises - let me explain …

After a few final solder joints, and a quick check over of the layout and components, I launched into Paul Ruby’s excellent Amp Power on Procedure. Paul is a man who has built many amps, and came up with this checklist and step by step process to powering up a tube amp for the first time without destroying all of your expensive parts. I took it by the book.

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OK, its been a while - the move went smoothly, but was a lot of work. After I dealt with the essentials, such as somewhere to cook, and sleep, then the nice to haves (somewhere to watch TV, an office to work in) I was free to start work on the garage, or electronics lab as I like to call it now

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Building upon my successful board creation of last weekend, I have now completed the soldering of the main board - which puts me back where I was many, many weeks ago. This whole exercise is becoming somewhat episodic as work and home commitments phase in and out, preventing me from the rapid progress I had originally envisaged. Be that as it may however, I am still just as motivated to finish this as I was in the beginning, I now see that I am in this for the long haul. I will be moving house in 3 weeks or so, and everything will become frantic around here, so I doubt I will find a lot of time to work on this until after that madness is over, however, when in the new house I will have a lot more space for working and actually prefer the idea of initial switch on and testing in my well appointed new garage with permanent bench bristling with test equipment, rather than the folding table I have now.

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This afternoon I completed the turret board - hurrah! I’m now in a position to rebuild the board to the higher standard I crave. With the correct tools, making the turret board turned out to be pretty easy, I would say an hour from start to finish. The first step was to accurately place the plan on the board as a drilling guide.

 
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Busy few days … Steve Vai was awesome and the trip to Atlantic city was a lot of fun. Work reared its ugly head however and I had to cancel most of my remaining vacation. This weekend however I made some progress. First, I assembled the drill press - not as trivial a task as you might imagine! It was pretty cheap but does the job really well. Surprisingly, the laser is a lot more than a gimmick as it lets you pretty accurately place the thing you are drilling. I did a test drilling of some fibreglass board to see how it would work out. Went pretty well, but my holes were not in straight lines - the trick for that is to clamp a piece of wood to the press as a straight edge - I’ll do that for the real board. Here is a pic of the assembled drill press, drilled board and the “X marks the spot” laser sighting.

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Ok, back from my vacation. While I was away, I took delivery of an oscilloscope and signal generator. Neither are essential for building an amplifier, but they can be useful for scoping input vs output, measuring gain and also for setting and checking tube biases. Besides, I wanted an excuse to get another Oscilloscope! The Scope was bought from a nice guy on AX84.com, and I bought the signal generator from Ebay.

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A big push today - I spent the day wiring up the chassis, ready to drop the new board in when I have it done. Still waiting parts for that, but the wiring went well. All told it took me about 6 hours to do this - partly because I was getting used to making the twisted looms, but also because there is a lot of nitpicking, and I wanted to do a good job of routing the wires. It doesn’t look a lot for 6 hours work, and looks messy because there are a lot of loose wires waiting to be soldered to the board, but I’m pretty pleased with it. The hardest part was the heater filaments (green and grey twisted wires) - I didn’t get those perfect but they should work fine.

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Today I ordered a drill press. Its got a laser so it must be good. I sent an order to Mouser Electronics for new board components - the big caps were about $10 each - ouch! So I revise my estimate to about $50 of components and some more for the turrets and board. It will probably be after the weekend before I get all of this together, so my weekend task will be to wire up the chassis, I can use my existing board as a guide, I just won’t hook it up. Once all the wiring is done, it shouldn’t take long to hook all the wires up to the new board when I have built it.

Having thought about it a little more, I’m not 100% happy with my efforts below. The joints were fine and electrically sound I am sure, but I did not like the eyelet board much. It will only get worse as I start attaching wires - some of those holes are already running out of space. Add to that I am using 18awg wire - only necessary for the heater circuits but I figured thicker wire would be better so decided to use it throughout.

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